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Screening Assessment for the Challenge

1,4-Benzenediamine, N,N’-mixed Phenyl and tolyl derivatives
and
1,4-Benzenediamine, N,N`-mixed tolyl and xylyl derivatives

Chemical Abstracts Service Registry Number
68953-84-4
and
68478-45-5

Environment Canada
Health Canada

September 2011


(PDF Version - 654 KB)

Table of Contents

Synopsis

Pursuant to section 74 of the Canadian Environmental Protection Act, 1999 (CEPA 1999), the Ministers of the Environment and of Health have conducted a screening assessment on 1,4-Benzenediamine, N,N’-mixed phenyl and tolyl derivatives (BENPAT), Chemical Abstracts Service Registry Number[1] 68953-84-4 and 1,4-Benzenediamine, N,N`-mixed tolyl and xylyl derivatives (BENTAX), Chemical Abstracts Service Registry Number 68478-45-5.

These substances were identified as a high priority for screening assessment and included in the Challenge initiative under the Chemicals Management Plan because they were found to meet the ecological categorization criteria for persistence, bioaccumulation potential and inherent toxicity to non-human organisms and are believed to be in commerce in Canada.

These substances were not considered to be a high priority for assessment of potential risks to human health, based upon application of the simple exposure and hazard tools developed for categorization of substances on the Domestic Substances List.

BENPAT and BENTAX are classified as Unknown or Variable Composition, Complex Reaction Products, or Biological Materials (UVCBs), and they are used in Canada and elsewhere in rubber product manufacturing. BENPAT and BENTAX function as antidegradants (antiozonants and antioxidants) in rubber products. These substances are not naturally produced in the environment. Between 100 and 1000 kg of BENTAX, and between 1 000 000 and 10 000 000 kg of BENPAT were imported into Canada in 2006. The quantities of BENPAT and BENTAX imported into Canada, along with the potentially dispersive uses of these substances, indicate that they could be released into the Canadian environment.

Based on experimental degradation data as well as their physical and chemical properties, components of both BENPAT and BENTAX are not expected to degrade quickly in the environment. They are persistent in water, soil and sediments. Major components of BENPAT and BENTAX also have the potential to accumulate in organisms, although this is expected to occur to only a moderate extent. These substances have been determined to meet the persistence, but not the bioaccumulation criteria as set out in the Persistence and Bioaccumulation Regulations. In addition, experimental toxicity values indicate that these substances are highly hazardous to aquatic organisms. Experimental aquatic toxicity data for BENPAT and a chemical analogue, indicate that both BENPAT and BENTAX have the potential to cause harm to aquatic organisms.

For this screening assessment, reasonable worst-case exposure estimates were selected in which industrial operations (users of the substance) discharge BENPAT into the aquatic environment. In the release scenarios considered, the predicted environmental concentration in water (PEC) was typically above the predicted no-effect concentrations (PNECs) calculated for algae. Based on a similar approach for BENTAX, the PEC in water was below the PNECs calculated for algae, using a more conservative exposure scenario.

Based on the information available, it is concluded that BENPAT is entering the environment in a quantity or concentration or under conditions that have or may have an immediate or long-term harmful effect on the environment or its biological diversity. It is concluded that BENTAX is not entering the environment in a quantity or concentration or under conditions that have or may have an immediate or long-term harmful effect on the environment or its biological diversity.

Chronic studies for BENPAT and an analogue indicated no evidence of carcinogenicity in experimental animals and available information on genotoxicity indicates that BENPAT and BENTAX are not likely to be genotoxic. As general population exposure to BENTAX was considered to be negligible, the risk to human health was considered to be low. Margins of exposure between upper-bounding estimates of exposure to BENPAT via environmental media and critical effects levels in experimental animals are considered to be adequate to address uncertainties in the health effects and exposure databases.

Based on the information presented in this screening assessment, it is concluded that BENTAX and BENPAT are not entering the environment in a quantity or concentration or under conditions that constitute or may constitute a danger in Canada to human life or health.

Based on the information available, it is concluded that BENPAT meets one or more of the criteria set out in section 64 of theCanadian Environmental Protection Act, 1999.

Based on the information available, it is concluded that BENTAX does not meet any of the criteria set out in section 64 of CEPA 1999.

In addition, it is concluded that the components of BENTAX and BENPAT meet the criteria for persistence, but not the criteria for the bioaccumulation potential as out in the Persistence and Bioaccumulation Regulations.

Since BENTAX is listed on the Domestic Substances List, its import and manufacture in Canada are not subject to notification under subsection 81(1). Given the potential ecological hazards of this substance, there is concern that new activities that have not been identified or assessed could lead to this substance meeting the criteria set out in section 64 of the Act. Therefore, it is recommended to amend the Domestic Substances List, under subsection 87(3) of the Act, to indicate that subsection 81(3) of the Act applies with respect to this substance so that new manufacture, import or use BENTAX is notified and undergoes ecological and human health risk assessments.

Introduction

The Canadian Environmental Protection Act, 1999 (CEPA 1999) (Canada 1999) requires the Minister of the Environment and the Minister of Health to conduct screening assessments of substances that have met the categorization criteria set out in the Act to determine whether these substances present or may present a risk to the environment or to human health.

Based on the information obtained through the categorization process, the Ministers identified a number of substances as high priorities for action. These include substances that

  • met all of the ecological categorization criteria, including persistence (P), bioaccumulation potential (B) and inherent toxicity to aquatic organisms (iT), and were believed to be in commerce in Canada; and/or
  • met the categorization criteria for greatest potential for exposure (GPE) or presented an intermediate potential for exposure (IPE) and had been identified as posing a high hazard to human health based on classifications by other national or international agencies for carcinogenicity, genotoxicity, developmental toxicity or reproductive toxicity.

The Ministers therefore published a notice of intent in theCanada Gazette, Part I, on December 9, 2006 (Canada 2006), that challenged industry and other interested stakeholders to submit, within specified timelines, specific information that may be used to inform risk assessment, and to develop and benchmark best practices for the risk management and product stewardship of those substances identified as high priorities.

The substances 1,4-Benzenediamine, N,N’-mixed Phenyl and tolyl derivatives an.

1,4-Benzenediamine, N,N`-mixed tolyl and xylyl derivatives were identified as high priorities for assessment of ecological risk as they were both found to be persistent, bioaccumulative and inherently toxic to aquatic organisms and are believed to be in commerce in Canada. It was decided to assess the substances together because of similarities in composition, structure and properties.

The Challenge for these substances was published in theCanada Gazette on September 26, 2009 (Canada 2009a, 2009b). Substance profiles were released at the same time. The substance profiles presented the technical information available prior to December 2005 that formed the basis for categorization of the substances. As a result of the Challenge, submissions of information pertaining to the properties, persistence, and uses of the substance 1,4-Benzenediamine, N,N’-mixed Phenyl and tolyl derivatives, and to the uses of the substance 1,4-Benzenediamine, N,N`-mixed tolyl and xylyl derivatives, were received (Study Submission 2010a, 2010b).

Although BENTAX and BENPAT were determined to be a high priority for assessment with respect to the environment, they did not meet the criteria for GPE or IPE and high hazard to human health based on classifications by other national or international agencies for carcinogenicity, genotoxicity, developmental toxicity or reproductive toxicity. Therefore, this assessment focuses principally on information relevant to the evaluation of ecological risks.

Screening assessments focus on information critical to determining whether a substance meets the criteria as set out in section 64 of CEPA 1999. Screening assessments examine scientific information and develop conclusions by incorporating a weight-of-evidence approach and precaution.[2]

This screening assessment includes consideration of information on chemical properties, hazards, uses and exposure, including the additional information submitted under the Challenge. Data relevant to the screening assessment of these substances were identified in original literature, review and assessment documents, stakeholder research reports and from recent literature searches, up to January 2011 for ecological and human health sections of the document. Key studies were critically evaluated; modelling results may have been used to reach conclusions. When available and relevant, information presented in hazard assessments from other jurisdictions was considered. The screening assessment does not represent an exhaustive or critical review of all available data. Rather, it presents the most critical studies and lines of evidence pertinent to the conclusion.

This screening assessment was prepared by staff in the Existing Substances Programs at Health Canada and Environment Canada and incorporates input from other programs within these departments. The ecological portion of this assessment has undergone external written peer review/consultations. Additionally, the draft of this screening assessment was subject to a 60-day public comment period. While external comments were taken into consideration, the final content and outcome of the screening assessment remain the responsibility of Health Canada and Environment Canada. Approaches used in the screening assessments under the Challenge have been reviewed by an independent Challenge Advisory Panel.

The critical information and considerations upon which the assessment is based are summarized below.

Substance Identity

Substance name

For the purposes of this assessment, the substance 1,4-Benzenediamine, N,N’-mixed phenyl and tolyl derivatives (CAS RN 68953-84-4) will be referred to as BENPAT, derived from the Domestic Substance List (DSL) (see Table 1). Similarly, the substance 1,4-Benzenediamine, N,N`-mixed tolyl and xylyl derivatives (CAS RN 68478-45-5) will be referred to as BENTAX, also derived from the DSL.

Both BENPAT and BENTAX are of Unknown or Variable Composition, Complex Reaction Products, or Biological Materials (UVCBs). For this assessment, another UVCB substance, 1,4-Benzenediamine,N,N’-mixed phenyl, tolyl and xylyl derivatives (CAS RN 68953-83-3), is used as an analogue, based on structural similarities. This analogue will be referred to as BENPATAX, derived from its National Chemical Inventories’ name.

The substance BENPAT is a mixture of phenyl and tolyl derivatives, and the substance BENTAX is a mixture of tolyl and xylyl derivatives. The analogue substance BENPATAX exists as a mixture of three derivatives, phenyl, tolyl and xylyl that are attached to the aromatic amine structure that is common to all three substances, BENPAT, BENTAX and BENPATAX (NICNAS 2001). The substance BENPATAX includes all the major components of both BENPAT and BENTAX. Therefore, this substance can be used as an analogue to both BENPAT and BENTAX. However, given that numerous studies were available for BENPAT, and that BENTAX is a data-poor substance, information pertaining to BENPATAX is used for the purpose of characterizing BENTAX only.

Information regarding substance identity for BENPAT, BENTAX and the analogue substance BENPATAX is described below in Tables 1a, 1b, and 1c, respectively.

Existing combinations of derivatives overlap for all three substances BENPAT, BENTAX and BENPATAX, and they include the following constituent possibilities: two phenyls (Structure 1), a phenyl and a tolyl (Structure 2), two tolyls (Structure 3), a tolyl and a xylyl (Structure 4), and two xylyls (Structure 5). There is only one combination of derivatives possible for the analogue substance BENPATAX that is not present in either BENPAT or BENTAX, and it is phenyl and xylyl.

In addition, most of the single constituents that form the substances BENPAT, BENTAX and BENPATAX have also been assigned CAS registry numbers. Hence, Structure 1 is known as N,N’-diphenyl-p-phenylenediamine (DPPD), CAS RN 74-31-7, Structure 2 (with methyl group in the ortho position on the aryl ring) is known as N-phenyl-N’-(o-tolyl)-p-phenylenediamine, CAS RN 27173-16-6, and finally Structure 3 (with methyl groups in the ortho position on aryl rings) is known as N,N’-di(o-tolyl)-p-phenylenediamine, CAS RN 15017-02-4.

Table 1a. Substance identity for BENPAT

Chemical Abstracts Service Registry Number (CAS RN)68953-84-4
DSL name1,4-Benzenediamine, N,N'-mixed Phenyl and tolyl derivatives
National Chemical Inventories (NCI) names[1]1,4-Benzenediamine, N,N'-mixed Ph and tolyl derivs. (TSCA, DSL, REACH, EINECS, ENCS, PICCS, ASIA-PAC, NZIoC);
Benzene-1,4-diamine, derives mixtes de N,N'-(phenyle et tolyle) (French) (DSL);
benzenediamine-1,4, melange de N,N'-derives phenyles et tolyles (French) (EINECS);
1,4-Benzoldiamin, N,N'-gemischte Phenyl und Tolylderivate (German) (EINECS);
1,4-bencenodiamina, N,N'-mezcla de fenil y tolil derivados (Spanish) (EINECS);
1,4-Benzenediamine, N,N'-mixed phenyl and tolyl derivatives (AICS);
1,4-Benzenediamine, N,N'-mixed phenyl and tolyl derivs. (ECL;)
DERIVATIVES, BENZENE-1,4-DIAMINE, N,N'-MIXED PHENYL AND TOLYL (PICCS);
MIXED PHENYL AND TOLYL P-PHENYLENEDIAMINE (PICCS)
Other namesHydroquinone, o-toluidine, aniline condensate;
N,N'-Diphenyl-p-phenylenediamine, methylated;
Amines (Chemical Category);
Wingstay 100 (Huntink et al. 2006, IUCLID Data Set 2003);
Polystay 100AZ (MSDS 2002a);
Accinox 100, blend of phenyl and tolyl p-phenylenediamines, DAPD, mixed diaryl-p-phenylenediamines, mixed di-aryl-p-phenylenediamines, diaryl-p-phenylenediamines, Naugard 496, Vulkanox 3100,Polystay 100, WTR Number 4a, Nailax (Nailax B)(Iuclid Data Set 2003), DTPD (XingChun Chemical Corporation c2006, Kirk-Othmer c2010)
Chemical group (DSL Stream)Organic Unknown or Variable Composition, Complex Reaction Products, or Biological Materials (UVCB)
Major chemical class or useAmines
Major chemical sub-classAromatic amines
Chemical formulaComplex reaction product that includes the following:

Structure 1
= C18H16N2

Structure 2 = C19H18N2

Structure 3 = C20H20N2
Representative chemical structure used to run the estimation models[2]

Structure 1
Chemical structure 68953-84-4 (Structure 1)

Structure 2
Chemical structure 68953-84-4 (Structure 2)

Structure 3
Chemical structure 68953-84-4 (Structure 3)

Representative SMILES used to run the estimation models[3]Structure 1
N(C1=CC=CC=C1)C1=CC=C(NC2=CC=CC=C2)C=C1

Structure 2CC1=C(NC2=CC=C(NC3=CC=CC=C3)C=C2)C=CC=C1

Structure 3CC1=CC=CC=C1NC1=CC=C(NC2=CC=CC=C2C)C=C1
Molecular mass (g/mol)Structure 1 = 260.33
Structure 2 = 274.36
Structure 3 = 288.39
[1] National Chemical Inventories (NCI) 2009: AICS (Australian Inventory of Chemical Substances); ASIA-PAC (Asia-Pacific Substances Lists); ECL (Korean Existing Chemicals List); EINECS (European Inventory of Existing Commercial Chemical Substances); ELINCS (European List of Notified Chemical Substances); ENCS (Japanese Existing and New Chemical Substances); PICCS (Philippine Inventory of Chemicals and Chemical Substances); and TSCA (Toxic Substances Control Act Chemical Substance Inventory).
[2] This substance is a UVCB (Unknown or Variable Composition,Complex Reaction Products, orBiological Materials); i.e., it is not a discrete chemical and thus may be characterized by a variety of structures. To assist with modelling, the structure and corresponding SMILES presented here were chosen to represent the substance.
[3] Simplified Molecular Input Line Entry System.

Table 1b. Substance identity for BENTAX

Chemical Abstracts Service Registry Number (CAS RN)68478-45-5
DSL name1,4-Benzenediamine, N,N'-mixedTolyl and xylyl derivatives
National Chemical Inventories(NCI) names[1]1,4-Benzenediamine, N,N'-mixed tolyl and xylyl derivs. (TSCA, DSL, REACH, EINECS, PICCS, ASIA-PAC)
Benzene-1,4-diamine, derives N,N'-(tolyles et de xylyles) mixtes (French) (DSL)
benzenediamine-1,4, derives N,N'-(melange de tolyl et de xylyl) (French) (EINECS)
1,4-Benzoldiamin, N,N'-gemischte Tolyl und Xylylderivate (German) (EINECS)
1,4-bencenodiamina, N,N'-mezcla de tolil y xilil derivados (Spanish) (EINECS)
1,4-Benzenediamine, N,N'-mixed tolyl and xylyl derivs. (ECL)
DERIVATIVE, BENZENE-1,4-DIAMINE, N,N'-MIXED TOLYL AND XYLYL (PICCS)
Other namesHydroquinone, o-toludine, xylidine condensate
p-Phenylenediamine, diaryl-Benzene-1,4-diamine, derives N,N'-(tolyles et de xylyles) mixtes
Amines (Chemical Category)
Chemical group (DSL Stream)Organic Organic Unknown or Variable Composition, Complex Reaction Products, or Biological Materials (UVCB)
Major chemical class or useAmines
Major chemical sub-classAromatic amines
Chemical formulaComplex reaction product that includes the following:

Structure 3 =
C20H20N2
Structure 4 = C21H22N2
Structure 5 = C22H24N2
Representative chemical structure used to run the estimation models[2]

Structure 3
Chemical structure 68478-45-5 (Structure 3)

Structure 4
Chemical structure 68478-45-5 (Structure 4)

Structure 5
Chemical structure 68478-45-5 (Structure 5)

Representative SMILES used to run the estimation models[3]Structure 3CC1=CC=CC=C1NC1=CC=C(NC2=CC=CC=C2C)C=C1

Structure 4CC1=CC=C(NC2=CC=C(NC3=CC=CC=C3C)C=C2)C(C)=C1

Structure 5CC1=CC=C(NC2=CC=C(NC3=CC=C(C)C=C3C)C=C2)C(C)=C1
Molecular mass (g/mol)Structure 3 = 288.39
Structure 4 = 302.41
Structure 5 = 316.44
[1] National Chemical Inventories (NCI). 2009: AICS (Australian Inventory of Chemical Substances); ASIA-PAC (Asia-Pacific Substances Lists); ECL (Korean Existing Chemicals List); EINECS (European Inventory of Existing Commercial Chemical Substances); ELINCS (European List of Notified Chemical Substances); ENCS (Japanese Existing and New Chemical Substances); PICCS (Philippine Inventory of Chemicals and Chemical Substances); and TSCA (Toxic Substances Control Act Chemical Substance Inventory).
[2] This substance is a UVCB (Unknown or Variable Composition,Complex Reaction Products, orBiological Materials); i.e., it is not a discrete chemical and thus may be characterized by a variety of structures. To assist with modelling, the structure and corresponding SMILES presented here were chosen to represent the substance.
[3] Simplified Molecular Input Line Entry Syste.

Table 1c. Substance identity for analogue substance BENPATAX

Chemical Abstracts Service Registry Number (CAS RN)68953-83-3
DSL name1,4-Benzenediamine, N,N'-mixed Phenyl and tolyl and xylyl derivatives
National Chemical Inventories (NCI) names[1]1,4-Benzenediamine, N,N'-mixed Ph and tolyl and xylyl derivs. (TSCA, DSL, REACH, EINECS, ASIA-PAC)
Benzene-1,4-diamine, derives mixtes de N,N'-(phenyle, tolyle et xylyle) (French) (DSL)
benzenediamine-1,4, melange de N,N'-derives phenyles, tolyles et xylyles (French) (EINECS)
1,4-Benzoldiamin, N,N'-gemischte Phenyl und Tolyl und Xylylderivate (German) (EINECS)
1,4-bencenodiamina, N,N'-mezcla de fenil, tolil y xilil derivados (Spanish) (EINECS)
1,4-Benzenediamine, N,N'-mixed phenyl and tolyl and xylyl derivs. (AICS)
1,4-Benzenediamine, N,N'-mixed Ph and tolyl and xylyl derivs. (ECL)
Other namesDiaryl-p-phenylenediamines
Hydroquinone, o-toluidine, xylidine, aniline condensate
Amines (Chemical Category)
Wingstay 200 (NICNAS 2001)
Polystay 200 (MSDS 2002b)
Chemical group (DSL Stream)Organic Unknown or Variable Composition, Complex Reaction Products, or Biological Materials (UVCB)[2]
Major chemical class or useAmines
Major chemical sub-classAromatic amines
Chemical formulaComplex reaction product:
C18H16N2 – C22H24N2
Representative chemical structure

where:
R = H (phenyl)
R = CH3 (tolyl)
R = 2 CH3 (xylyl)

Chemical structure 68953-83-3

Molecular mass
(g/mol)
260.33 – 316.44 (based on individual structures)
302 (NICNAS 2001)
[1] National Chemical Inventories (NCI). 2009: AICS (Australian Inventory of Chemical Substances); ASIA-PAC (Asia-Pacific Substances Lists); ECL (Korean Existing Chemicals List); EINECS (European Inventory of Existing Commercial Chemical Substances); ELINCS (European List of Notified Chemical Substances); ENCS (Japanese Existing and New Chemical Substances); PICCS (Philippine Inventory of Chemicals and Chemical Substances); and TSCA (Toxic Substances Control Act Chemical Substance Inventory).
[2] This substance is a UVCB (Unknown or Variable Composition,Complex Reaction Products, orBiological Materials); i.e., it is not a discrete chemical and thus may be characterized by a variety of structures. To assist with modelling, the structure and corresponding SMILES presented here were chosen to represent the substance.

The substances BENPAT and BENTAX are produced through the condensation process of 1 mol of hydroquinone with 2 to 2.5 mols of a mixture of arylamines containing equal parts of either aniline and o-toluidine, or o-toluidine and xylidine, respectively (Goodyear Tire and Rubber Company 1965, Fernandes and McCormack 1971, Kirk-Othmer c2010). The xylidine reactant used in the production of BENTAX could either be 2,4-dimethyl aniline or a mixture of xylidine isomers (Goodyear Tire and Rubber Company 1965).

Since the arylamines present in the reactions are in equal proportions, a random distribution of products should result. Accordingly, the composition of BENPAT has been reported as 25% N,N’-diphenyl-p-phenylenediamine (Structure 1, CAS RN 74-31-7), 50% of N-phenyl-N’-(o-tolyl)-p-phenylenediamine (Structure 2, CAS RN 27173-16-6) and 25% N,N’-di(o-tolyl)-p-phenylenediamine (Structure 3, CAS RN 15017-02-4) (Huntink et al. 2006, IUCLID Data Set 2003).

Based on the compositional information for BENPAT and the ratios of o-toluidine and xylidine in the reaction mixture, the substance BENTAX is assumed to be composed of approximately 25% N,N’-di(o-tolyl)-p-phenylenediamine (Structure 3, CAS 15017-02-4), 50% N-(o-tolyl)-N’-xylyl-p-phenylenediamine, and 25% N,N’-dixylyl-p-phenylene (CAS 28726-30-9). Although the N-(o-tolyl)-N’-xylyl-p-phenylenediamine and N,N’-dixylyl-p-phenylene components of BENTAX are potentially composed of several different isomers, they are represented in this assessment by the isomers N-(o-tolyl)-N’-(2,4-dimethylphenyl)-p-phenylenediamine (Structure 4) and N,N’-(2,4-dimethylphenyl)-p-phenylenediamine (Structure 5), respectively. It should be noted that BENTAX may be composed of additional combinations of isomers resulting from varying substitution patterns of the methyl substituents in tolyl and xylyl derivatives, however the modelled physico-chemical properties would not differ significantly based on these slight differences in substitution. Such variability in the composition of BENPAT is not expected since the specific reactants and their methyl substitution patterns are known for this substance (Goodyear Tire and Rubber Company 1965, Fernandes and McCormack 1971, Kirk-Othmer c2010, Huntlink et al. 2006, IUCLID Data Set 2003).

Finally, impurities found in BENPAT include two residual reactants o-toluidine (<0.1%) and aniline (<0.1%), and additional reaction products including methyldiphenylamine (<0.1%) and diphenylamine (1-5%) (IUCLID Data Set 2003). Similarly, it was reported that o-toluidine was a residual component in BENTAX at <0.1% (MSDS 2002a). Since these impurities are present at very low amounts in the overall composition of BENPAT and BENTAX, they will not be further addressed in the present assessment.

Physical and Chemical Properties

Substances BENPAT and BENTAX are UVCBs, characterized by a combination of phenyl and tolyl, and tolyl and xylyl derivatives, respectively. The analogue substance BENPATAX is a UVCB consisting of a mixture of phenyl, tolyl and xylyl derivatives.

Some physico–chemical properties were available for the commercially available products of all three substances (IUCLID Data Set 2003, European Commission 2000, Goodyear Tire and Rubber Company 1965, NICNAS 2001 and Study Submission 1998); however in some instances exact constituent compositions of the commercial products were not specified or the physico–chemical properties were approximated based on measurements of individual constituents. Therefore, experimental and modelled physico-chemical properties for the substances BENPAT, BENTAX, and the analogue substance BENPATAX are described below in two tables; in Table 2a data available for the commercial products are presented, and next in Table 2b, data available for representative Structures 1 through 5 are presented (see Table 1a, 1b, 1c for descriptions of the representative structures). The experimental and modelled data (as well as general information) available for the representative Structures 1 – 3 are considered relevant and are used as ‘read-across’ for the substance BENPAT while those for the representative Structures 3 – 5 are considered relevant for the substance BENTAX.

The physico–chemical properties described in Tables 2a and 2b are relevant to the environmental fates of the substances. Also, models based on quantitative structure-activity relationships (QSAR) were used to generate data for some of the physical and chemical properties of the five representative structures of BENPAT and BENTAX (see Table 2b). These models (except WSKOWWIN 2008) are mainly based on fragment addition methods, i.e. they rely on the structure of a chemical. Since these models only accept the neutral form of a chemical as input (in SMILES form), the modelled values shown in Table 2b are for the neutral form of the representative structures.

Table 2a. Physical and chemical properties for commercially available forms of BENPAT, BENTAX and BENPATAX

PropertySubstance (CAS RN)TypeValueTemperature (°C)Reference
Melting point
(ºC)
BENPAT (68953-84-4)Experimental90[*] – 105* IUCLID Data Set 2003, European Commission 2000
BENTAX (68478-45-5)Experimental60[*] – 70[a]Goodyear Tire and Rubber Company 1965
Boiling point
(ºC)
BENPATAX (68953-83-3)Experimental>300 NICNAS 2001, Study Submission 1998
Vapour pressure
(Pa)
BENPATAX (68953-83-3)Modelled<1 x 10-5[*]
(<1 x 10-8 kPa)[b]
25NICNAS 2001, Study Submission 1998
Log Kow[c]
(Octanol-water partition coefficient)(dimensionless)
BENPAT (68953-84-4)Experimental3.4 – 4.3 IUCLID Data Set 2003
3.3[*] – 4.6[*]Study Submission 2010c
BENPATAX (68953-83-3)3.5 – 4.5MSDS 2002b
3.5 – 4.56NICNAS 2001, Study Submission 1998
Log Koc [d]
(Organic carbon-water partition coefficient)
(dimensionless)
BENPAT (68953-84-4)Experimental4.39 – 4.95 Study Submission 2010c
Water solubility (mg/L)BENPAT (68953-84-4)Estimated based on experimental data~2.2[e], [*] Study Submission 2010a
BENTAX (68478-45-5)Experimentalinsoluble MSDS 2002a
BENPATAX (68953-83-3)Experimentalinsoluble MSDS 2002b
1.02[*]~20NICNAS 2001, Study Submission 1998
Solubility in pentane (g/mL)BENPAT (68953-84-4)Experimental0.0025 Goodyear Tire and Rubber Company 1965
BENTAX (68478-45-5)0.031 
BENPATAX (68953-83-3)0.013 – 0.027 
Abbreviations: Koc, organic carbon-water partition coefficient; Kow, octanol–water partition coefficient.
[a] Melting point of alkyl-substituted diphenyl-p-phenylenediamines prepared using an amine mixture of mixed toluidines and mixed xylidines is below 60°C. Melting point of alkyl-substituted diphenyl-p-phenylenediamines prepared using an amine mixture of 2,4-dimethyl aniline and o-toluidine ranges from 65 to 70° (Goodyear Tire and Rubber Company 1965).
[b] The value in brackets is the original reported value.
[c] Log Kow values presented in ranges were determined by high performance liquid chromatography ( HPLC) for the individual major components.
[d] Log Koc values presented in a range were determined by HPLC for the individual major components.
[e] It was indicated in the Study Submission (2010a) that this value was obtained from measured solubilities of BENPAT’s major components in the range of 0.045 – 0.013 mg/L and a combined solubility of minor components of 1.9 mg/L. Further details on how this value was established were not provided.
[*] indicates selected value for modelling

Table 2b below describes empirical and modelled properties of representative Structures 1 through 5 for the substances BENPAT and BENTAX (see Tables 1a and 1b for descriptions of the representative structures).

Table 2b. Physical and chemical properties for representative structures of BENPAT[1] (Structures 1 – 3) and BENTAX[2] (Structures 3 – 5)

PropertyStructureTypeValue[1]Temperature (°C)Reference
Melting point
(ºC)
1Experimental154[*] Lorenz and Parks 1962
150 – 151 Merck Index V.12:2 in CHRIP c2008
144 – 153 Kirk-Othmer c2010
Modelled143 MPBPWIN 2008
2Experimental130[*] Lorenz and Parks 1962
Modelled154 MPBPWIN 2008
3Experimental135[*]-136[*] Lorenz and Parks 1962
Modelled159 MPBPWIN 2008
4Modelled169[*] 
5179[*] 
Boiling point
(ºC)
1Experimental220-225
(@0.5mmHg)
 Merck Index V.12:2 in CHRIP c2008
Modelled398 MPBPWIN 2008
2Modelled410 
3Experimental420 CHRIP c2008
Modelled421 MPBPWIN 2008
4Modelled433 
5445 
Vapour pressure
(Pa)
1Experimental8.47 x 10-7
(extrapolated)
  
Modelled7.65 x 10-5[*]25MPBPWIN 2008
2Modelled3.06 x 10-5[*]25MPBPWIN 2008
31.42 x 10-5[*]
45.65 x 10-6[*]
52.23 x 10-6[*]
Henry’s Law constant
(Pa·m3/mol)
1Modelle.2.08 x 10-525HENRYWIN 2008
22.29 x 10-5
32.53 x 10-5
42.79 x 10-5
53.08 x 10-5
Log Kow
(Octanol-water partition coefficient)
(dimensionless)
1Experimental> 3.722.8IUCLID Data Set 2003
3.4 Study Submission 2010b, IUCLID Data Set 2003
3.3[*] Study Submission 2010c
3.50 Study Submission 1998
Modelled4.04 KOWWIN 2008
2Experimental> 4.322.8IUCLID Data Set 2003
3.82 Study Submission 2010b, IUCLID Data Set 2003
3.92 Study Submission 1998
3.9[*]Study Submission 2010c
Modelled4.59 KOWWIN 2008
3Experimental> 4.622.8IUCLID Data Set 2003
4.28 Study Submission 2010b, IUCLID Data Set 2003
4.6[*] Study Submission 2010c
4.17 – 4.21Study Submission 1998
Modelled5.13 KOWWIN 2008
4Experimental4.39 – 4.42 Study Submission 1998
Modelled5.68 KOWWIN 2008
5Experimental4.51 – 4.56 Study Submission 1998
Modelled6.23 KOWWIN 2008
Log Koc (Organic carbon-water partition coefficient) (dimensionless)1Experimental4.39 Study Submission 2010c
Modelled4.7151
(from MCI[**])
KOCWIN 2008
3.1165
(from log Kow)
2Experimenta.4.66 Study Submission 2010c
Modelled4.92
(from MCI)
KOCWIN 2008
3.42
(from Log Kow)
3Experimenta.4.95 Study Submission 2010c
Modelled5.14
(from MCI)
KOCWIN 2008
3.72
(from Log Kow)
4Modelled5.35
(from MCI)
 KOCWIN 2008
4.02
(from Log Kow)
5Modelled5.55
(from MCI)
 KOCWIN 2008
4.33
(from Log Kow)
Water solubility (mg/L)1Experimental0.13[*] Study Submission 2010a
Modelled7.35325WSKOWWIN
2008
1.5867WATERNT 2008
2Experimental0.11[*] Study Submission 2010a
Modelled2.0925WSKOWWIN
2008
Modelled0.50WATERNT 2008
3Experimental0.045[*] Study Submission 2010a
Modelled0.5925WSKOWWIN 2008
Modelled0.16WATERNT 2008
4Modelled0.1725WSKOWWIN
2008
Modelled0.05[*]WATERNT 2008
5Modelled0.0525WSKOWWIN
2008
Modelled0.02[*]WATERNT 2008
pKa2[3]ModelledpKa1 = 1.91 ACD/pKaDB 2005
pKa2 = -1.29
3[3]pKa1 = 2.24
pKa2 = -1.22
[1] BENPAT is composed of representative Structures 1 – 3. See Table 1a for descriptions of the representative structures.
[2] BENTAX is composed of representative Structures 3 – 5. See Table 1b for descriptions of the representative structures.
[3] In water, BENPAT and BENTAX (represented by Structures 2 and 3 for the purpose of ACD/pKaDB [2005] modelling) behave as a base attracting protons and ,therefore, the secondary pKa values decrease (opposite trend would be observed for an acid).
[*] indicates selected value for modelling
[**] MCI = Molecular Connectivity Index

Modelled and experimental data for the physico-chemical properties of the representative Structures 1 – 5 indicate the following general qualities of the structures: low water solubility, very low to negligible vapour pressure and Henry’s law constant, moderate to very high log Koc and moderate to high log Kow. Moreover, based on the results obtained from the modelling program pKa DB from ACD (2005), using Structure 2 and Structure 3 as representative of the substances BENPAT and BENTAX, respectively, it is concluded that both substances ionize very little in water and should therefore be considered non-ionizing.

Solubility of a substance influences its mobility in the environment. Therefore, it is one of the key parameters in the characterization of the chemical’s fate when it is released into the environment.

The aqueous solubilities of BENPAT and analogue substance BENPATAX were determined experimentally and a full study was submitted to Environment Canada for BENPATAX (Study Submission 1998), whereas an IUCLID study summary was submitted for BENPAT (Study Summary 2010a). Both studies were carried out according to the Organisation for Economic Cooperation and Development (OECD) guideline no. 105 for determining water solubility; BENPATAX was tested with the original protocol of the guideline, adapted in 1981. OECD guideline no.105 has since been revised and adopted in 1995 with changes mainly pertaining to the format (OECD 1995). OECD guideline no. 105 features column elution method with High Performance Liquid Chromatography (HPLC) (UV detection).

For BENPAT, it was determined experimentally that representative Structures 1 – 3 (major components) have water solubilities in the range of 0.045 – 0.13 mg/L and minor components have water solubility of about 1.9 mg/L. Moreover, it was determined that the overall water solubility of BENPAT was about 2.2 mg/L. Since the experimental details were not provided, it is not clear how this higher water solubility value was established. It was also not explained why the overall water solubility of BENPAT, a multi-component substance, was higher than any of the individual components that make up the substance. Average overall water solubility for BENPATAX was determined as 1.02 mg/L (Study Submission 1998) and given that BENPATAX is composed of major components that are more methyl-substituted and less water soluble than those found in BENPAT, it was consistent for both BENPAT and BENPATAX that the overall water solubilities were higher than those of the individual components. Details of how the overall water solubility of BENPATAX was established from the HPLC peaks of individual components were not provided in the full study (Study Submission 1998).

The water solubility study for BENPATAX was critically reviewed for validity. This review (Robust Study Summary) is found in Appendix I.

Finally, there are differences between the available experimental water solubility values for representative Structures 1 – 3 and modelled water solubility values, where the experimental values are approximately a magnitude lower that the modelled ones. Experimental values were used in model inputs for representative Structures 1 – 3, and modelled values (from the model WATERNT 2008) were used for representative Structures 4 and 5. Therefore, water solubilities for Structures 4 and 5 may be overestimations; however these values are equivalent to, or lower than, the water solubility values for representative Structures 1 – 3 and are in agreement with the general trend that the more methyl-substituted compounds should display lower water solubility.

Sources

BENPAT

The substance BENPAT is not naturally produced in the environment. Based on information collected through a survey conducted pursuant to section 71 of CEPA 1999 (Canada 2009b), seven notifiers indicated that between 1,000,000 and 10,000,000 kg of BENPAT were imported into Canada in 2006. The substance was not reported to be manufactured in Canada. Additionally, one company identified stakeholder interest in BENPAT.

Elsewhere, BENPAT has been identified as a high production volume (HPV) chemical on the lists from the following organisations: the US Environmental Protection Agency (US EPA) (US EPA 2009), the European Commission Joint Research Centre (ESIS) (ESIS c1995–2009), and the Organisation for Economic Co-operation and Development (OECD) (OECD 2004a).

In the past, information received from the Domestic Substances List nomination (1984–1986) indicated that the total quantity of BENPAT reported as imported into, manufactured in or in commerce in Canada during the calendar year 1986 was in the range of 100 000 – 1 000 000 kg (Environment Canada 1988). The number of notifiers for the calendar years 1984 – 86 was four.

BENTAX

The substance BENTAX is also not naturally produced in the environment. Between 100 and 1000 kg of BENTAX were imported into Canada in 2006, as identified through a survey conducted pursuant to section 71 of CEPA 1999 (Canada 2009b). BENTAX was not reported to be manufactured in Canada. Fewer than four notifiers responded to the survey and one company identified stakeholder interest in BENTAX.

In 2005, between 1001 – 100 000 kg of BENTAX were imported into Canada as identified in a survey conducted pursuant to section 71 of CEPA 1999 for that year (Environment Canada 2005).

BENTAX has not been reported as a HPV chemical or low production volume chemical by EU Industry (ESIS c1995-2009). It was also not found on HPV lists from other organisations such as US EPA or OECD.

Finally, in the past, the quantity reported to be manufactured, imported or in commerce in Canada during the calendar year 1986 was between 100 000 and 1 000 000 kg (Environment Canada 1988). The number of notifiers for the calendar years 1984-86 was fewer than four.

Uses

In Canada, industrial uses of the substances BENPAT and BENTAX were identified as a result of section 71 survey under CEPA 1999 (Canada 2009b); most of these uses are considered confidential business information and cannot be disclosed. However, all uses were taken into consideration in conducting this assessment.

One company reported that the substance BENPAT is used in rubber product manufacturing in concentrations of 0.29 to 2.17% (Environment Canada 2010c). One of the uses of the substance BENTAX was reported as an antidegradant in rubber compounding to impart aging protection by retarding degradation due to exposure to heat, oxygen, ozone, ultra-violet radiation or moisture in finished materials.

In general, the substances BENTAX and BENPAT are used as additives to protect elastomers against ozone deterioration (Kirk-Othmer c2010). They are commonly referred to as antiozonants or antioxidants as the protective effects on rubber products ensue from a reaction of the chemical additive with ozone.

BENPAT and BENTAX belong to a class of commercial chemical antiozonants that are derivatives of N,N’-diaryl-p-phenylenediamine (N,N’-diaryl-p-PDA), where the aryl group may be phenyl, methylphenyl, or napthalenyl (Miller et al. 1985). They are moderately active antiozonants, used at low concentrations due to their poor water solubility (Kirk-Othmer c2010). Their main advantage was recognized to be high resistance to loss by consumption and vaporization (Ambelang et al. 1963). Thus, in combination with more reactive antiozonants, they offer an increased protection in longer-term applications such as radial passenger tires (Miller et al. 1985).

BENPAT is known to be used as an antioxidant/antiozonant in high durability rubber products including tires and hoses (Iatropoulos et al. 1997). It should be noted that rubber protective agents, i.e. antioxidants and antiozonants are typically added to make up approximately 1% (wt-%) of a typical tire thread composition (Wik and Dave 2009). However, as different chemicals may be used as protective agents and processing aids, the composition of different tires varies (Wik and Dave 2009).

BENTAX and BENPAT were not notified as ingredients in cosmetic products in Canada (CNS 2010) and do not appear on the Cosmetic Ingredient Hotlist, Health Canada’s administrative list of ingredients that are intended to be prohibited or restricted for use in cosmetics in Canada (Health Canada 2009). BENTAX and BENPAT are not currently used in any pest control products registered for use in Canada as either active ingredients or formulants (PMRA 2007). BENTAX and BENPAT are not listed as approved food additives under Division 16 of the Food and Drug Regulations (Canada 1978). BENTAX and BENPAT were not identified in food packaging applications or as incidental additives (April 2010 email from Food Directorate, Health Canada, to Risk Management Bureau, Health Canada; unreferenced).

BENTAX and BENPAT are not listed in the Drug Product Database (DPD), the Therapeutic Products Directorate's internal Non-Medicinal Ingredient Database, the Natural Health Products Ingredients Database or the Licensed Natural Health Products Database as medicinal or non-medicinal ingredients present in final pharmaceutical products, natural health products or veterinary drugs (DPD 2010; NHPID 2010; LNHPD 2010; April 2010 email from Therapeutic Products Directorate, Health Canada to Risk Management Bureau, Health Canada, unreferenced).

In the past, industrial use codes for substance BENPAT and BENTAX were identified through Domestic Substance List nomination data (Environment Canada 1988). These included the following applications that may still be relevant: ‘antioxidant/corrosion inhibitor/tarnish inhibitor/scavenger/antiscaling agent’ and ‘organic chemicals/industrial’.

In the Nordic countries, industrial use of the substance BENPAT was indentified as ‘manufacture of rubber and plastic products’, with the use category defined as antioxidants (antiozonants) (SPIN 2006).

Releases to the Environment

A method has been developed by Environment Canada to estimate a substance’s losses during different stages of its life cycle, including its fate within a finished product or article (Environment Canada 2008). This method consists of a life cycle analysis and a spreadsheet tool (Mass Flow Tool or MFT) that integrates information on the manufacturing, importation and use data available for the substance. Starting with an identified mass of the substance, each life cycle stage is subsequently evaluated until all of the mass is accounted for. Relevant factors are considered, uncertainties recognized and assumptions may be made during each stage, depending on information available. The estimated losses represent a complete mass balance over the life cycle of the substance and include releases to wastewater and other receiving compartments (land, air), chemical transformation, transfer to recycling activities and transfer to waste disposal sites (landfill, incineration). However, unless specific information on the rate or potential for release of the substance from landfills and incinerators is available, the method does not quantitatively account for releases to the environment from disposal.

In general, releases of a substance to the environment depend upon various losses from its manufacture, industrial use, and/or consumer/commercial use. These losses can be grouped into seven types: (1) discharge to wastewater; (2) emission to air; (3) loss to land; (4) chemical transformation; (5) disposal to landfill; (6) loss to incineration; and (7) disposal through recycling (i.e., recycling is deemed a loss and therefore not considered further in the present assessment). They are estimated using regulatory survey data, industry data and data published by different organizations. The discharge to wastewater refers to raw wastewater prior to any treatment, whether it be on-site industrial wastewater treatment or off-site municipal wastewater treatment. In a similar manner, the loss via chemical transformation refers to changes in a substance's identity that may occur within the manufacture, industrial use, and consumer/commercial use stages, but excludes those during waste management operations such as incineration and wastewater treatment. The loss to land includes unintentional transfer or leakage to soil or paved/unpaved surfaces during the substance’s use and service life (e.g., from the use of agricultural machinery or automobiles). The loss to land, however, does not include transfers subsequent to a substance’s use and service life (e.g., land application of biosolids and atmospheric deposition).

The losses estimated for the substances BENPAT and BENTAX over their lifecycle (based on conservative assumptions) are presented in Table 3 (Environment Canada 2010a, 2010b). Neither BENPAT nor BENTAX are manufactured in Canada above the reporting threshold, so the estimated losses are based on import quantities reported for the year 2006. The 2006 volumes reported in Canadian commerce were between 1 000 000 and 10 000 000 kg/year for BENPAT and between 100 and 1000 kg/year for BENTAX (Canada 2009b).

Table 3. Estimated Losses of BENPAT and BENTAX during their Lifecycle[1]

Type of LossProportion (%)
BENPATBENTAX
Industrial useCommercial/Consumer useTotalIndustrial useCommercial/Consumer useTotal
Wastewater0.03 – 0.65.6 – 5.7[*]5.6 – 6.30.04 – 0.81.3 – 2.41.3 – 3.2
Land-5.50 – 5.53[**]5.50 – 5.53---
Air0.004 – 0.1 0.004 – 0.10.04 – 0.1-0.04 – 0.1
Chemical Transformation[***]Non-zeroNon-zero Non-zeroNon-zero 
Incineration0.001 – 0.0048.28 – 8.338.28 – 8.330.002 – 0.022.9 – .2.9 – 3
Landfill0.5 – 0.612.3 – 12.512.8 – 13.10.08 – 1.592.3 – 95.693.8 – 95.7
Recycling-67.0 – 67.467.0 – 67.4---
ExportUnknownUnknown UnknownUnknown 
[1] For BENPAT and BENTAX, information from the following key documents was used to estimate releases to the environment and the distribution of the substance, as summarized in this table: OECD 2004b, c, d; US EPA 2007 and ChemRisk LLC 2010. Note that ChemRisk LLC 2010 documents are developed by industry for their use in the European Registration, Evaluation, Authorisation and Restriction of Chemical substances (REACH) context. Other documentation has provided information for some assumptions.
[*] For the consumer/commercial use scenario developed for BENPAT, it is expected that in some locations across Canada roadway run-off is collected by the municipal wastewater treatment plants, but in some locations this run-off could be discharged untreated directly into ambient waters.
[**] For the consumer/commercial use scenario developed for BENPAT, the type of loss denoted as ‘Land’ generally refers to streets, roads and associated nearby soil.
[***] Potential chemical transformation of antiozonants BENPAT and BENTAX stemming from the process of oxidation is acknowledged; however, at the present time the extent to which it occurs is not adequately documented in the available literature.

The majority of BENPAT in commercial/consumer products is estimated to be recycled (approximately 67%). BENPAT is also estimated to be released onto land and into roadway run-off water at approximately equal proportions of 5.5 % and 5.7 %, respectively, as a result of consumer or commercial use of products containing this substance. It should be noted that for the consumer/commercial use scenario developed for BENPAT, ‘Land’ generally refers streets, roads and associated soil nearby. Moreover, in the consumer/commercial release scenario, approximately 13% of BENPAT is estimated to be disposed of in landfills and about 8% is estimated as destined for incineration. Overall releases of BENPAT estimated from industrial activities or uses are less than 1% to each of wastewater and landfill and up to 0.1% to air.

BENTAX is estimated to be released to wastewater at 1.3 – 3.2% of the total quantity used in Canadian commerce. In contrast to BENPAT, BENTAX in commercial/consumer products is estimated to primarily end up at waste disposal facilities (incineration at approximately 3% and landfill at 93.8 – 95.7%). Finally, releases of BENTAX from industrial uses are estimated at up to 0.8% to wastewater and similarly to BENPAT, emissions to air are estimated at up to 0.1%.

The above loss estimates indicate that BENPAT and BENTAX have a potential for release to the environment. In general, wastewater is a common source for releases of a substance to water and soil through wastewater treatment facilities and the subsequent waste management of sludge. Tire rubber particles containing BENPAT can be deposited on the side of roads and washed into sewers. BENPAT can subsequently leach out once the rubber particles come into contact with water (Wik 2007). A small fraction of rubber tire particles may be transferred by wind or rain to nearby soil, however concentrations of these particles tend to decrease with distance from the roads, and reductions of greater than 80% have been reported at 30m from roads (Wik and Dave 2009). As a result of recycling activities, a substance could find its way to water or soil, depending upon the operational characteristics of facilities. Finally, landfills have the potential to leach substances into groundwater, most likely in instances when the landfill has no liner and/or leachate collection system. However, offgassing or migration of BENPAT and BENTAX from landfills is not expected to be a significant source of release, as both substances have low volatility and adsorb highly to soils.

Although there is the possibility that other consumer/commercial products containing BENPAT or BENTAX may be imported into Canada in addition to those reported as a result of industry surveys conducted pursuant to section 71 of CEPA 1999, no information is available on the quantity of such imports. It is anticipated that the life cycle stages and proportional losses resulting from use of these other products would not be significantly different from those considered and estimated above. However, the actual mass of the substance lost from each of the life cycle stages may be higher than the estimates provided above, if such information was available for consideration.

Environmental Fate

Level III fugacity modelling (EQC 2003) simulates the distribution of a substance in a hypothetical, evaluative environment according to chemical partitioning, reactivity and inter-media transport processes. The mass-fraction values shown in Tables 4a, 4b, 4c and 4d represent the net effect of these processes under conditions of continuous release when a non-equilibrium “steady-state” has been achieved (i.e., Level III). Model inputs for to EQC (2003) are provided in Appendix II. Since a variety of data on commercial products and representative structures of BENPAT and BENTAX were available, the model was run a number of times in order to understand the range of likely behaviour/ fate of these substances.

In general, the results of Level III fugacity modelling indicate little variation and suggest that both BENPAT and BENTAX are expected to predominantly reside in water, soil, and sediment, depending on the compartment of release.

EQC modelling results for BENPAT from Tables 4a and 4b and results for BENTAX from Tables 4c and 4d are described collectively below.

Table 4a describes fugacity modelling results of the substance BENPAT based on physico-chemical properties available for the commercial product, and Table 4b describes fugacity modelling results of the representative Structures 1 – 3 of BENPAT, presented in ranges. Similarly, Table 4c describes fugacity modelling results of the substance BENTAX, based on physico-chemical properties available for the commercial product, and results for representative Structures 3 – 5 of BENTAX are summarized in Table 4d.

Table 4a. Results of the Level III fugacity modelling of BENPAT (presented in ranges)[*] (EQC 2003)

Substance released to:Percentage of substance partitioning into each compartment
AirWaterSoilSediment
Air (100%)0.21.4 – 2.797<1.4
Water (100%)negligible67 – 94negligible6 – 33
Soil (100%)negligiblenegligible100negligible
[*] Some of the experimental physico-chemical properties of the substance BENPAT were available as ranges; consequently the upper and lower limits of the ranges were used as model inputs (see Table 2a and Appendix II).

Table 4b. Results of the Level III fugacity modelling of representative Structures 1 – 3 of BENPAT (presented in ranges)[*] (EQC 2003)

Substance released to:Percentage of substance partitioning into each compartment
AirWaterSoilSediment
Air (100%)1.2 – 4.61.7 – 4.291 – 960.2 – 1.6
Water (100%)negligible50 – 950.74 – 49
Soil (100%)negligible<1100negligible
[*] EQC model results are combined for representative Strucutures 1 – 3 and shown in ranges (see Table 2b and Appendix II for model inputs).

Table 4c. Results of the Level III fugacity modelling of BENTAX (EQC 2003)

Substance released to:Percentage of substance partitioning into each compartment
AirWaterSoilSediment
Air (100%)0.41.4971.2
Water (100%)negligible52.5negligibe.47.5
Soil (100%)negligiblenegligible100negligible

Table 4d. Results of the Level III fugacity modelling of representative Structures 3 – 5 for BENTAX (presented in ranges)[*] (EQC 2003)

Substance released to:Percentage of substance partitioning intoeach compartment
AirWaterSoilSediment
Air (100%)<1.21.696<1.6
Water (100%)negligible50 – 60<140 – 50
Soil (100%)negligiblenegligible100negligible
[*] EQC model results are combined for representative Strucutures 3 – 5 and shown in ranges (see Table 2b and Appendix II for model inputs).

If released to air, low or negligible amounts of BENPAT and BENTAX are expected to reside in air (see Tables 4a – 4d). Based on the negligible to low modelled vapour pressures for the representative Structures 1 – 5 in the rage of 0.2 x 10-5 – 8 x 10-5 Pa and Henry's Law constants in the range of 2x10-5 – 3x10-5Pa·m3/mol, BENPAT and BENTAX are considered non-volatile. Therefore, if released solely to air, BENPAT and BENTAX will reside in this compartment only in very small fractions. Soil is the major compartment into which these substances are expected to be distributed (>90 %, see Tables 4a – 4d) from releases to air.

If released into water, BENPAT and BENTAX are expected to adsorb to suspended solids and sediment based upon moderate to high estimated log Koc values of 3.1 – 4.3 (obtained from log kow) and 4.7 – 5.5 (obtained from MCI) for representative Structures 1 – 5. Experimental log Kocvalues of 4.39 – 4.95 for the representative Structures 1 – 3 of BENPAT also support this trend. Upon release into water, these substances are also predicted to remain in the water compartment at steady state. Volatilization from water surfaces is expected to be an unimportant fate process based upon estimated Henry's Law constants for BENPAT and BENTAX. Thus, if water is the receiving medium, BENTAX and BENPAT are expected to mainly reside in water and in sediment, with negligible fractions in air and soil (see Table 4a – 4d). However, BENPAT is expected to be more soluble in water than BENTAX due to the lower degree of methyl-substitution of its components, which translates to lower Kow and Koc values. This is illustrated by the results of the Level III fugacity modelling (see Tables 4a and 4b), where it is predicted that when released to water, BENPAT would tend to reside more in this compartment (50 – 95%), with a smaller fraction occurring in sediment (up to 49 %), whereas BENTAX would tend to reside in water and sediment in approximately equal fractions (50 – 60 % and 40 – 50%, respectively).

If released to soil, BENPAT and BENTAX are expected to have high to moderate adsorptivity to soil (i.e., expected to be relatively immobile) based upon their estimated log Kocvalues. Volatilization from moist soil surfaces seems to be an unimportant fate process based upon the estimated Henry's Law constants of the representative structures. Moreover, BENPAT and BENTAX are not expected to volatilize from dry soil surfaces based upon the vapour pressures of their representative structures and the analogue substance BENPATAX. Therefore, if released to soil, BENPAT and BENTAX will mainly reside in the soil compartment, as illustrated by the results of the Level III-fugacity modelling (see Tables 4a – 4d).

Persistence and Bioaccumulation Potential

Environmental Persistence

In water

Empirical degradation data were available for the substance BENPAT. No degradation data were available for the substance BENTAX. Empirical data on some of the representative structures, namely Structure 1 and Structure 3, were also available; Structures 1 and 3 are partly representative of BENPAT and Structure 3 is partly representative of BENTAX. In addition, empirical degradation data for the analogue substance BENPATAX are included. These data are considered appropriate for both BENPAT and BENTAX, however, they are will be used for BENTAX only since the same types of studies are available for BENPAT.

Table 5a presents the empirical degradation data for the substance BENPAT, analogue substance BENPATAX as well as representative Structures 1, and 3.

For BENPAT, 0 – 0.64 % biodegradation over 28 days in a ready-biodegradation test was reported (IUCLID Data Set 2003, Study Summary 2010b). For BENTAX, data available for the analogue substance BENPATAX were used based on the structural similarities of the substances, namely presence of xylyl and tolyl derivatives. Biodegradation of 1.72 % over 28 days in water was reported for BENPATAX (NICNAS 2001). All biodegradation studies in water were conducted according to the OECD Guideline 301.

Empirical biodegradation data for the representative Structure 1 and photodegradation data for the representative Structure 3 were also available. Structure 1 was shown to degrade slowly with 0.2% biodegradation over two weeks in a test performed according to the OECD TG 301C guideline (CHRIP c2008). The conclusion from this test was ‘non-biodegradability’.

A photodegradation study performed in water was available for the representative Structure 3, a major component of both BENPAT and BENTAX (Study Submission 2010a). Relatively short half-lives of 2.5 and 4.7 days were obtained under two aquatic study conditions characterised by pH 6 and pH 8, respectively. However, this mode of degradation would only be applicable to the fraction of the substance found at the top of the water column and available to sunlight. Considering physico-chemical properties of Structure 3 (see Table 2), in particular its low water solubility, and resulting environmental fate predicted by the EQC modelling (see Table 4c), where partitioning to sediment is expected when this substance is released into water, it is expected that a limited amount of the substance would be available in a water column for photodegradation. In addition, transformation products of the substance were not identified in this study.

Table 5a. Empirical data for degradation of BENPAT, analogue substance BENPATAX and representative Structures 1 and 3[1]

SubstanceMediumFate processDegradation valueDegradation endpoint / unitsReference
BENPATWaterBiodegradation[2]0.64Biodegradation
28 day/ %
IUCLID Data Set 2003, Study Submission 2010b
WaterBiodegradation0Biodegradation
28 day/ %
IUCLID Data Set 2003
BENPATAXWaterBiodegradation1.72Biodegradation
28 day/ %
NICNAS 2001
Structure 1WaterBiodegradation0.2Biodegradation
14 day/ %
CHRIP c2008
Structure 3WaterPhoto-degradation2.5, 4.5[3]Half-life / daysStudy Submission 2010a
[1] Structure 1 is partially representative of the substance BENPAT and Substance 3 is partially representative of both substances BENTAX and BENPAT
[2] Biodegradation was evaluated using OECD 301F respiratory method and inoculum obtained from activated sludge from a waste water treatment plant.
[3] Half-lives measured at pH 6 and 8, respectively

A hydrolysis study of BENPAT was performed over 28-day period (Study Submission 2010c). Analysis of the aqueous BENPAT solution showed a decrease of the initial concentrations of BENPAT’s representative Structures 1 – 3 to 34 – 39% within the first 7 days of the study and a further, slower concentration decline in the subsequent days. However, no degradation products were detected in the aqueous solution as BENPAT disappeared. Instead, precipitates of the three representative Structures were found on the surface of the glassware used in the study. These results indicated that chemical reactions did not occur between BENPAT and water under the experimental conditions; rather physical precipitation of the substance took place. As BENPAT does not have the functional groups that undergo hydrolysis, it is expected that the hydrolysis reaction would be unlikely for this substance.

Since relatively few experimental data on the degradation of BENPAT and BENTAX are available, a QSAR-based weight-of-evidence approach (Environment Canada 2007) was also applied using the degradation models shown in Table 5b below. Given the ecological importance of the water compartment, the fact that most of the available models apply to water and the fact that both BENPAT and BENTAX are expected to be released to this compartment, biodegradation in water was primarily examined. Both substances BENPAT and BENTAX do not contain functional groups expected to undergo hydrolysis. In addition, there is a general lack of information on the degradation of these substances in sediments.

Table 5b summarizes the results of available QSAR models for degradation in water and air. Since both BENTAX and BENPAT exist as mixtures, individual components of the mixtures, i.e. representative Structures 1 – 5 were examined with QSAR models.

Table 5b. Modelled data for degradation of representative Structures 1 – 5.

Fate ProcessModel and model basisRepresentative StructureModel ResultModel PredictionExtrapolated Half-life (days)
Air
Atmospheric oxidationAOPWIN 2008[1]Structures 1 – 3t 1/2 = 0.053 days (or 0.64 hrs) ≤ 2
Structures 3 – 5
Ozone reactionAOPWIN 2008[1]Structures 1 – 3n/a[2] n/a
Structures 3 – 5
Water
HydrolysisHYDROWIN 2008[1] n/a[2] n/a
Primary biodegradation 
Biodegradation (aerobic)[3]BIOWIN 2008[1]
Sub-model 4:
Expert Survey
(qualitative results)
Structures 1 – 33.07 – 3.26biodegrades slowly< 182
Structures 3 – 52.90 – 3.07
Ultimate biodegradation
Biodegradation (aerobic)[3]BIOWIN 2008[1]
Sub-model 3:
Expert Survey
(qualitative results)
Structures 1– 32.14 – 2.39“biodegrades slowly”≥ 182
Structures 3 – 51.93 – 2.14
Biodegradation (aerobic)[4]BIOWIN 2008[1]
Sub-model 5:
MITI linear probability
Structures 1 – 3-0.27 - -0.26“biodegrades very slowly”≥ 182
Structures 3 – 5-0.27 - -0.29
Biodegradation (aerobic)[4]BIOWIN 2008[1]
Sub-model 6:
MITI non-linear probability
Structures 1 – 30.002 – 0.003“biodegrades very slowly”≥ 182
Structures 3 – 50.001 – 0.002
Biodegradation (aerobic)[4]TOPKAT 2004
Probability[*]
Structures 1, 20“biodegrades slowly”≥ 182
Structures 4, 5
Biodegradation (aerobic)CATABOL c2004 – 2008
% BOD
(biological oxygen demand)
Structures 1 – 30.0038 – 0.007“biodegrades very slowly”≥ 182
Structures 3 – 50.0036 – 0.0038
[1] EPIsuite (2008)
[2] Model does not provide an estimate for this type of structure.
[3] Output is a numerical score from 0 to 5.
[4] Output is a probability score.
[*] TOPKAT 2004 prediction for Structure 3 was found to be unreliable and was excluded

In water, a predicted hydrolysis half-life could not be determined for the representative structures of BENPAT and BENTAX as the model HYDROWIN (2008) does not estimate hydrolysis rate constants for these types of structures (no hydrolysable functional groups present).

Ultimate biodegradation model results from models BIOWIN 2008 Sub-models 3, 5, 6, TOPKAT 2004 and CATABOL c2004 – 2008 obtained for the representative structures of BENPAT and BENTAX are very consistent and suggest slow or very slow biodegradation in water and that the half-life would be >182 days for complete mineralization in this compartment. The results of the BIOWIN Sub-model 4 (primary survey model) would suggest that the substance has a primary half-life of <182 days, however the identity of the degradation products is unknown. The rate of primary biodegradation is relatively slow and when extrapolated to complete mineralization, the half-life is expected to be >182 days.

Using an extrapolation ratio of 1:1:4 for a water: soil: sediment biodegradation half-life (Boethling et al. 1995), the half-life in soil is also >182 days and the half-life in sediments is >365 days. This indicates that the components of BENPAT and BENTAX are expected to be persistent in soil and sediment.

Overall, the experimental and modeled biodegradation data for the substance BENPAT, the analogue substance BENPATAX as well as some of the data on individual representative Structures 1 and 3 (Table 5a) indicate that the ultimate biodegradation half-lives in water for the components of BENPAT and BENTAX are likely to be longer than 182 days (6 months).

In other compartments

Air

In air, a predicted atmospheric oxidation half-life value of 0.053 days for all five representative structures (see Table 5b) demonstrates that the components of BENPAT and BENTAX are likely to be rapidly oxidized. Even though the ozone reaction could not be estimated for the representative structures using the model AOPWIN, based on their mode of action as anti-ozonants and anti-oxidants in rubber products, the substances are expected to react with other photo-oxidative species in the atmosphere, such as O3.Also, based on results from photolysis experiments in water using representative Structure 3, the components of the substances BENPAT and BENTAX are likely to degrade via direct photolysis. These degradation processes will further reduce the half-life of BENPAT and BENTAX in the atmosphere. With a half-life of less than 0.053 days via reactions with hydroxyl radicals, and potentially via photolysis and reaction with ozone, components of BENPAT and BENTAX are considered not persistent in air.

Soil

Behaviour of the representative Structure 3, a major component of both BENPAT and BENTAX, in soil was studied in a soil dissipation study performed in field conditions in North Carolina (US) according to the US EPA guideline 164-1 (Springborn Laboratories 2004). The test substance was radiolabelled with C14 and applied to the top of sandy loam soil test samples at the nominal concentration of 165 µg of substance/kg dry weight. Total radioactivity was measured in soil samples at 0 – 3 inches and 3 – 6 inches over a period of 362 days (at days 0, 7, 14, 32, 61, 90, 180 and 362). Concentrations below 6 inches of soil were not measured. Soil sampling over 362 days indicated that most (98%) of the radiolabelled material remained in the top 3 inches of the soil. Most of the radioactivity applied (>95%) became quickly bound to the soil and unextractable. The unbound, extractable radiolabelled substance dissipated quickly, with 5% remaining after 32 days, 3% after 180 days and less than 1% after 362 days. The concentrations of the extractable radioalabelled representative Structure 3 in the top 3 inches of the soil were used to calculate the dissipation rates and corresponding dissipation half-lives assuming pseudo-first order kinetics. Initial dissipation rate from day 0 to day 32 of the study was 0.064 day-1 and the corresponding dissipation half-life was 10.8 days, the dissipation rate between days 32 and 362 was 0.00788 day-1 and the corresponding dissipation half-life was 88 days and the dissipation rate between days 0 and 362 was calculated as 0.0104 day-1 with the corresponding dissipation half-life of 66.5 days. It was noted that the dissipation rate decreased between days 32 and 180 of the study with the net dissipation half-life of 217 days and increased between days 180 and 362, with a net dissipation half-life of 58 days. This slowing and acceleration in the dissipation of the representative Structure 3 was in part attributed to the seasonal changes in temperature, as these study periods corresponded to spring and autumn conditions.

At the end of the study, 46% of the initial radioactivity remained in the upper 3 inches of the soil, less than 2% in the 3 – 6 inch layer. Over 95% of the radioactivity remaining in the top three inches of the soil samples was unextractable. Overall, there was no accumulation of extractable degradates, losses were presumed to be to the atmosphere as carbon dioxide or volatile organic degradates. However, monitoring of such compounds was not performed.

In summary, the dissipation study of the representative Structure 3 indicated that this substance has a high potential for binding to soil, it is likely relatively immobile in the soil column and that changes in the environmental conditions such as temperature can exert influence over its dissipation rates. High adsorptive potential to soil particles of both BENPAT and BENTAX is expected based on the high Koc values of the representative Structures 1 – 5. Lastly, the results of this study represent a mass-balance picture of the fate of the representative Structure 3 of BENPAT in soil. As such, this study does not address the intrinsic property of the representative Structure 3 to degrade in this environmental compartment.

Oxidation

Rubber antidegradants such as antiozonants and antioxidants function through sequential migration to the surface, which is initiated by a disruption of equilibrium within the rubber mix caused by the reaction of the chemical at the rubber surface (Ignatz-Hoover et al. 2003). There are several theories explaining the protective action of antiozonants at the rubber surface (Kirk-Othmer c2010). The scavenger theory suggests that the antiozonant diffuses to the surface of the rubber and ozone reacts preferentially with the antiozonant instead of the rubber. The protective film theory proposes that the ozone-antiozonant reaction products, generated as described in the scavenger theory, form a film on the surface of the rubber, which further prevents ozone attack of the rubber. The relinking theory presumes that the antiozonant can prevent scission of the ozonized rubber or recombine severed double bonds in the rubber. Finally, the self-healing theory supposes that the antiozonant can react with ozonized rubber or other reaction products to give a low molecular weight, inert self-healing film on the rubber surface (Kirk-Othmer c2010).

More than one of these proposed mechanisms may contribute to the protection of rubber; however the available evidence suggests that the scavenger theory is the most important mode of action (Kirk-Othmer c2010). Visual and microscopic evidence is also available for the presence of a film forming on the rubber surface. Upon spectroscopic characterization, the composition of this film was shown to consist of some un-reacted antiozonant as well as some reaction products observed in ozonized liquid antiozonant (Lattimer et al. 1980, Andries et al. 1975, Andries et al. 1979). The re-linking and self-healing theories are less established compared to the scavenger and protective film theories, as there is little evidence of a reaction between the antiozonant and ozonized rubber or that antiozonants can attach themselves to the rubber chains following ozone attack (Lorenz and Parks 1963a, 1963b).

The mechanism of anti-ozone activity of representative Structure 1 (or DPPD) was studied and its transformation products were characterized (Rotschová and Pospíšil, 1981). BENPAT and BENTAX are used as antiozonants in rubber (Kirk-Othmer c2010), and in their primary role as protective agents they undergo oxidation by ozone in lieu of the rubber (Rapta et al. 2009), similarly to the scavenger theory described above. As inferred from findings on Structure 1, this oxidation results in the formation of 1,4-benzoquinone diimine derivatives, which were shown to be stable to oxidation over a one year period with no further changes noted in the compounds’ composition (Rotschová and Pospíšil, 1981). In addition, it was found that Structure 1 forms N,N’-diphenyl-p-quinondiimine when it reacts with peroxy radicals (Kochi 1973, Boozer et al. 1955).

Long Range Transport Potential

The Transport and Persistence Level III Model (TaPL3) (TaPL3 2000) was used to estimate the Characteristic Travel Distance (CTD) defined as the maximum distance traveled in air by 63% of the substance. Beyer et al. (2000) have proposed CTDs of >2000 km as representing high long-range atmospheric transport potential (LRATP), 700-2000 km as moderate LRATP, and <700 km as low LRATP. Based on the CTD estimate of 60 km for the substance BENTAX, and 28 km for the substance BENPAT, the long-range atmospheric transport potential of both substances is considered to be low. This means that the substances BENTAX and BENPAT are not expected to be transported through the atmosphere a significant distance from its emission sources.

Conclusion

Based on the empirical data that includes representative Structures 1 and 3 and analog data, as well as modelled data (see Tables 5a and 5b), there is consistent and reliable evidence to show that substances BENPAT and BENTAX contain significant quantities of the components that meet the persistence criteria in water, soil and sediment (half-lives in soil and water ≥ 182 days and half-life in sediment ≥ 365 days), but do not meet the criteria for air (half-life in air ≥ 2 days) as set out in the Persistence and Bioaccumulation Regulations (Canada 2000).

Potential for Bioaccumulation

In the aquatic compartment

Experimental and modelled log Kow values for the representative Structures 1 – 3 of BENPAT and representative Structures 3 – 5 of BENTAX suggest that these chemicals have moderate to high potential to bioaccumulate in biota (see Tables 2a and 2b; experimental and modelled log Kow values range between 3.4 – 6.23).

Experimental bioaccumulation data for BENPAT is described below, whereas bioaccumulation studies were not identified for BENTAX. Subsequently, modelled bioconcentration factor (BCF) and bioaccumulation factor (BAF) values for both BENPAT and BENTAX are provided.

Experimental bioaccumulation data for BENPAT

Bioaccumulation of the substance BENPAT was studied in carp,Cyprinus carpio (Study Submission 2010b), and summarized in IUCLID Data Set (2003). MITI Method for Testing the Degree of Accumulation of Chemical Substances in Fish Bodies (analogous to the OECD 305C method) was used to measure BCF values for BENPAT at two test concentrations, 0.05 and 0.005 mg/L, over an 8 week period (IUCLID Data Set 2003, Study Submission 2010b). Ten fish were exposed at each test concentration, and 5 fish were used in the control group. The concentration of BENPAT in water was measured twice a week throughout the study, and the concentration of BENPAT in fish was analyzed during weeks 1, 2, 4, 6, and 8, each time in two fish, using high-performance liquid chromatography. Two control fish were analyzed at the initiation and termination of exposure. In addition, a depuration test was performed following the bioaccumulation test, where additional fish were subjected to analysis on days 1, 5, and 8 after the termination of exposure to clarify the clearance process of concentrated test substance from test fish (Study Submission 2010b).

It was indicated in the IUCLID Data Set (2003) summary that over the course of the study there were difficulties in maintaining the nominal concentrations of BENPAT in the test medium (test concentrations ranged from 60 to 100%) possibly due to rapid uptake by the fish and partitioning to tank surfaces. Moreover, since the test substance BENPAT is a complex reaction product, there was a high degree of variability in the data resulting in ranges of BCF values for different components of the product.

In the full report of the study (Study Submission 2010b), it was indicated that, in general, the concentration of test substances in test water decreases when they have a bioconcentration potential, likely as a result of rapid intake and metabolism.

Five peaks, a – e, were identified by HPLC: peaks a and b were identified as minor components and peaks c – e were identified as the major components. Furthermore, peak ‘c’ was identified as the representative Structure 1, peak ‘d’ was identified as the representative Structure 2, and peak ‘e’ was identified as the representative Structure 3 (Study Submission 2010b).

Overall, the ranges of BCF values obtained for each peak were equivalent at the two experimental exposure levels of 0.05 and 0.005 mg/L. Therefore, the most effective way to characterize the BCF for each representative structure is to present the average BCF values from both exposure levels.

For representative Structure 1, the average BCF was 1363±573, for representative Structure 2, the average BCF was 2472±890 and for representative Structure 3, the average BCF was 6250±2548, calculated from 20 BCF values ranging from 269 – 2630 for peak c, 776 – 3790 for peak d and 1420 – 11300 for peak e, respectively.

A depuration test was performed on BENPAT to clarify the clearance process of concentrated test substance from the test fish for exposure concentrations of 0.05 and 0.005 mg/L (Study Submission 2010b). The depuration half-lives obtained were as follows, at the 0.05 and 0.005 mg/L exposure concentrations, respectively: for the representative Structure 1,0.7 days and 3 days; for the representative Structure 2, 3.6 days and 5.7 days; and for the representative Structure 3, 44.4 days and 193 days (Study Submission 2010b).

These depuration results for BENPAT were also summarized in the IUCLID Data Set (2003). However, the half life of 193 days for the representative Structure 3 at 0.005 mg/L exposure concentration was excluded from the IUCLID Data Set (2003) summary, and instead it was indicated that this half-life was below 6 days. According to the IUCLID Data Set (2003), the depuration results indicated that half-lives were below 6 days for peaks a – e at exposure level of 0.005mg/L, and below 4 days for peaks a – d at exposure level of 0.05 mg/L, however depuration half-life for peak e at 0.05 mg/L exposure level was reported as 44 days. This half-life value for peak e was deemed as suspect in the IUCLID Data Set summary (2003) since it was much higher than the depuration half-life obtained for the same peak at 0.005 mg/L exposure level and inconsistent with the general depuration half-life trend of less than five days observed for peaks a – d at both exposure levels (IUCLID Data Set 2003). However, the half-life of 44 days (as well as 193 days) is consistent with the higher observed BCFs reported for the representative Structure 3 in Study Submission (2010b).

To address the substantial variation observed in the BCF values for each peak and to apply appropriate statistical methods in order to form a basis for interpretation of results, an additional project was undertaken entitled “Statistical Calculations of Data from a Bioaccumulation Study with Wingstay 100 in Carp” and summarized in IUCLID Data Set (2003). This analysis employed the Monte Carlo uncertainty analysis method. Results indicated a maximum BCF value of 6600 for peak e, and depuration data confirmed the attainment of tissue steady state levels of BENPAT components within three weeks, with depuration half-lives of less than 5 days for all components. It was also noted that as methyl substitution of the test substance increased so did the bioaccumulation in carp, and this trend was consistent with increasing log Kowvalues. Therefore, the results of the bioaccumulation study indicate that representative Structure 3, one of the major components of BENPAT (comprising ≥ 20% of BENPAT [Huntlink et al. 2006, IUCLID Data Set 2003]), is likely to bioaccumulate in carp, with a BCF value > 5000.

Additionally, experimental BCF values were available for the representative Structure 1. Carp, Cyprinus carpi, were tested at two concentrations 0.1 mg/L and 0.01 mg/L and the resulting highest BCF values were 1420 and 2150, respectively. The conclusion for Structure 1 was “moderate bioconcentration” (CHRIP c2008). These results for Structure 1 are generally consistent with the carp bioconcentration study described above (IUCLID 2003, Study Summary 2010b), i.e. since Structure 1 is the least substituted component of the substance BENPAT, the BCF values are expected to be moderate.

Table 6a presents the empirical BCF values for BENPAT in fish.

Table 6a. Empirical data for bioaccumulation of BENPAT and representative Structure 1

SubstanceTest organismEndpointValue wet weight (L/kg)Reference
BENPATCarp
(Cyprinus carpio)
average BCF[1]representative Structure 1
1363±573

representative Structure 2
2472±890

representative Structure 3[2]
6250±2548
IUCLID Data Set 2003, Study Submission 2010b
Structure 1Carp
(Cyprinus carpio)
BCF260 – 1420[3]
500 – 2150[4]
CHRIP c2008
[1] Average BCFs for each representative structure were calculated by combining the reported BCF values from two exposure levels, at 0.005 and 0.05 mg/L.
[2] BCF of ~7000 was obtained by applying Monte Carlo estimation to the range of BCF values for the representative Structure 3 (compound e) (IUCLID Data Set 2003).
[3] BCF measured for test concentration of 0.1 mg/L (ppm)
[4] BCF measured for test concentration of 0.01 mg/L (ppm)

Modelled bioconcentration and biomagnification data for representative structures of BENPAT (Structures 1 – 3) and BENTAX (Structures 3 – 5)

Since few BCF data for BENPAT were available and no bioaccumulation data were available for BENTAX, a predictive approach was applied using available bioaccumulation (BAF) and BCF models. According to the Persistence and Bioaccumulation Regulations (Canada 2000) a substance is bioaccumulative if its BCF or BAF is > 5000; however measures of BAF are the preferred metric for assessing bioaccumulation potential of substances. This is because BCF may not adequately account for the bioaccumulation potential of substances via the diet, which predominates for substances with log Kow > ~4.5 (Arnot and Gobas 2003).

Due to the structural similarities between the representative Structures of BENPAT, and BENTAX and their comparable log Kow values, predictions were generated for all of the representative Structures for these two commercial substances. A modified version of the kinetic mass-balance model developed by Arnot and Gobas (2003) was employed. Metabolic rate constants were calculated based on empirical study data by normalizing to the study weight, lipid content of fish and temperature of water as outlined in Arnot et al. (2008a), when BCF is known. This modeling is considered “in domain” because it is based on first principles and as long as the mechanistic domain (passive diffusion), global parameter domain (range of empirical log Kow and MW) and metabolism domain (corrected kM) are satisfied, predictions are considered valid (Arnot and Gobas 2003; Arnot and Gobas 2006).

The mean of whole body BCF values reported for the structures in Table 6a were used to generate metabolic rate constants. Gut and tissue metabolism is generally not an important elimination process for chemicals with log Kow less than approximately 4.5 (Arnot et al. 2008a, b; Arnot and Gobas 2006), but this can depend on the size and lipid content of fish used in testing.

From Table 6b it can been seen that the total elimination rate (depuration rate) constants, estimated by the mass-balance kinetic model normalized to fit the empirical study data, are over-estimated when compared with the empirical depuration rate reported for BENPAT’s representative Structures 1 – 3 (Study Submission 2010b). However, an estimate of kM must be less than the depuration rate constant. Thus, when growth-corrected, the kM[3] for representative Structures 1 – 3, based on the study conditions, is expected to be approximately 0.094 days-1. The QSAR-based estimate of kM for the representative structures of BENPAT and BENTAX using the BCFBAFWIN model (Arnot et. al. 2009), which uses only structure and log Kow for estimation, ranges from 2.3 to 0.17 days-1 providing further confidence of a relatively fast metabolic transformation rate. Based on the close structural similarity, log Kow and the likely biotransformation pathway (Phase 1 arene oxidation), the empirically-derived rate constant of 0.094 days-1 is used for all structures of BENPAT and BENTAX to represent the biotransformation potential of the fish in the empirical studies.

Since the metabolic potential, and thus elimination, can be related to the body weight and temperature (Hu and Layton 2001, Nichols et al. 2007), BCF and BAF predictions were further normalized to the middle trophic level fish in the Arnot-Gobas model according to the procedure outlined in Arnot et al. (2008b). The middle trophic level fish was used to represent the overall model output as suggested by the model developer. Moreover, it is the most representative of fish weight likely to be consumed by an avian or terrestrial piscivore.

The results of the mass-balance kinetic modelling are presented in Table 6c. These results indicate that at a kM of approximately 0.05 days-1, which is the metabolic rate constant normalized to the middle trophic level fish in the model, none of the representative structures of BENPAT and BENTAX have a BCF or BAF greater than 5000. Even when the metabolic rate constant is set to zero (i.e., kM = 0 days-1), the predicted BCF and BAF for a middle trophic level fish is close to, but still less than, 5000.

Table 6b: Kinetic rate constants and BCF and BAF calculated for BENPAT, BENTAX and BENPATAX based on available BCF data and normalized to study conditions.

SubstanceStudy End-
point[b]
Uptake Rate
Constants day-1 (k1)[a]
Total Elimi-
nation Rate Constant day-1 (kT)[a], [d]
Gill Elimi-
nation Rate Constant day-1(k2)[a]
Meta-
bolic Rate Constant day-1 (kM)[a]
Growth Rate Constant day-1(kG) [a]Fecal Egestion Rate Constant day-1(kE) [a]BCF
(study condi-
tions)[a]
BAF
(study condi-
tions)[a]
Refe-
rence
BENPAT:
representative Structure 1
BCF
(1363)
4316.016.00-5.7000.0010.0107281IUCLID Data Set 2003, Study Sub-
mission 2010b
BENPAT:
representative Structure 1
BCF
(1747)
3874.124.12-3.9160.0010.00895105CHRIP c2008
BENPAT:
representative Structure 2
BCF
(2472)
4510.4010.397-0.2260.0010.01010962344IUCLID Data Set 2003, Study Sub-
mission 2010b
BENPAT:
Representative Structure 3
BCF (6250)4520.3260.315-0.2550.0010.01013805888IUCLID Data Set 2003, Study Sub-
mission 2010b
BENPAT
(representative Structures 1, 2 and 3)
Depuration test4290.139[c]unknown[h]~0.094[i]0.035[e]0.012258[f] Study Sub-
mission 2010b
[a] calculated using mass-balance approach as outlined in Arnot et al. (2008a) when BCF is known and correcting for logkow and mean body weight, temperature and lipid content of fish in available studies
[b] reported from available data (geomean used when applicable)
[c] based on an average of reported depuration half-lives in Study Submission (2010b) (= 5 days)
[d] kT = sum of all elimination rate constants or k2 + kG when these are known
[e] growth rate not reported. Growth rate estimated based on the Challenge submission data for test fish of similar weight and fed at 2-3% body weight
[f] calculated as k1/k2 (i.e., kinetic BCF)
[h] this value cannot be accurately calculated because estimates are greater than the reported depuration rate constant in Study Submission 2010a
[i] this is an upper estimate of the metabolic rate constant for BENPAT as it must be less than 0.139 and does not consider gill elimination

Table 6c. Predicted BCF and BAF for representative structures of BENPAT (representative Structures 1 – 3) and BENTAX (representative Structures 3 – 5) for a representative middle trophic level (MTL) fish

SubstanceLog kowMetabolic Rate Constant day-1(kM) [a]BCF MTL [b]BAF MTL [b]Reference
BENPAT:
representative Structure 1
3.30.05130135Arnot and Gobas (2003)
BENPAT:
representative Structure 2
3.90.05501537Arnot and Gobas (2003)
BENPAT and BENTAX:
representative Structure 3
4.60.0516211905Arnot and Gobas (2003)
BENTAX:
representative Structure 4
4.40.0512021584Arnot and Gobas (2003)
BENTAX:
representative Structure 5
4.50.0.14121584Arnot and Gobas (2003)
[a] Based on a metabolic rate constant of 0.094 day-1 normalized to middle trophic level fish (W=184g, L=6.8%, T=10) according to procedure in Arnot et al. (2008b)
[b] calculated using a modified three trophic level mass-balance model from Arnot and Gobas (2003) normalized to middle trophic level fish (W=184g, L=6.8%, T=10)

Empirical BCF and Metabolism Database Verification

Arnot and Gobas (2006) critically evaluated available bioaccumulation data (BCF and BAF) for fish and other organisms. Part of this effort was stimulated by DSL Categorization activities in the early 2000s, and lead to an empirical database of quality BCF and BAF values that Canada has used for categorization and is now using for the Challenge (Arnot and Gobas 2003b). In the empirical database for BCF, at a log Kow of 4.5 to 4.6 (i.e., representative of Structures 3 – 5), the empirical distribution of “acceptable” fish BCF data shows that there are only two chemicals (tetrachlorobenzene and trichlorotoluene) with fish BCFs exceeding the Canadian criterion of BCF ≥5000 (there are many chemicals with BCFs lower than 5000 at this log Kow). Some of the reported BCFs for these two halogenated compounds are less than 5000 showing the variability in BCF testing. The metabolic transformation of these two compounds is expected to be much slower than BENPAT and BENTAX components. Indeed, examination of the kM database from Arnot et al. (2008b) for 10g fish at 15oC shows that these two halogenated chemicals have empirically-based metabolic rate constants (kM) predominantly in the range of 10-3 and QSAR predicted kM values for a 10g fish at 15oC ranging from 10-2 to 10-1. When normalized to a middle trophic level fish weighing 184g at 10oC, the kM values are even lower, ranging from 10-4 to 10-2. Therefore, considering comparable log Kow to the halogenated compounds, but given a much higher empirically-derived (and estimated) kM for BENPAT and BENTAX, there is no supporting empirical evidence to suggest that BENPAT or BENTAX would have a BCF exceeding 5000.

Mass-Balance Studies in Mammals

Studies in rabbits and rats have been undertaken to examine biological fate of the representative Structures 1 – 3 of BENPAT, including absorption, metabolism and excretion (Umeniwa et al. 1985, Research Triangle Institute 1998a, 1998b). To summarize, mammalian metabolism studies of the representative Structures 1 – 3 of BENPAT indicated that, following ingestion, these substances are excreted predominantly in feces and bile. These substances are also readily metabolised and metabolites are excreted in a fashion similar to the parent compounds. The above information cannot easily be used to explain the mass-balance in water-breathing organisms such as fish, where it is expected that gill exchange plays an important loss mechanism for BENPAT and BENTAX. Metabolic transformation rates are also expected to somewhat slower in fish than mammals. However, the information does support that these structures are metabolized in vivo and that loss through fecal egestion and urine in fish may be higher than that calculated by the mass-balance kinetic BCF model, suggesting that these factors mitigate bioaccumulation potential.

Conclusion

BENPAT and BENTAX

Modelled BCF and BAF values for the Structures 1 – 3, representative of the substance BENPAT are in the range of 130-1905. Predicted BCF and BAF values for BENPAT are essentially equal which suggests that uptake from the diet is not a factor for this UVCB and that BCF is the preferred metric for assessing bioaccumulation. Indeed, given the low to moderate log Kow values for BENPAT, the bioavailable fraction in the water as predicted using the Arnot-Gobas model is 99 – 100% for all representative structures.

Steady-state empirical BCF data available for BENPAT indicate that a major component, representative Structure 3, has the potential to bioaccumulate with a BCF > 5000. However, this empirical result does not agree with the overall depuration rate constant observed for the representative structures of BENPAT in the subsequent depuration rate study (Study Submission 2010b). This result also does not agree with the mean empirical BCF of approximately 2500 for the representative structure 2, which differs from the representative structure 3 by only a single methyl group and less than half a log unit of log Kow. When the depuration rate constant from this study was used to correct the Arnot-Gobas kinetic mass-balance model, the representative Structures 1 – 3 of BENPAT were predicted to have BCFs and BAFs of less than 5000. There exists some inconsistency in the available bioconcentration data for BENPAT. This is likely propagated by fluctuating exposure concentrations which were not well maintained during the test exposure period (reported to vary between 60 – 100% of the nominal test concentrations). The BCF result for representative structure 3 is, therefore, questionable in light of other evidence, especially all acceptable empirical evidence for low to moderate bioconcentration at log Kow of ~ 4.5 to 4.6.

Therefore, it is concluded that there is sufficient consistent physical-chemical, log Kow, biotransformation and modelled and in vivo evidence to suggest that none of the BENPAT or BENTAX representative structures meet the bioaccumulation criterion (BCF or BAF > 5000) as set out in the Persistence and Bioaccumulation Regulations (Canada 2000).

Potential to Cause Ecological Harm

Ecological Effects Assessment

A - In the Aquatic Compartment

There is modelled and experimental evidence that substances BENTAX and BENPAT cause harm to aquatic organisms following short-term (acute) and longer-term (chronic) exposure at relatively low concentrations. Empirical data available for BENPAT, the analogue substance BENPATAX, and representative Structure 1 for aquatic organisms are presented in Table 7. Although modelled predictions for aquatic toxicity were generated for both BENPAT and BENTAX, given the numerous experimental data available for the substances as well as the analogue substance BENPATAX (see Table 7), they are not included.

In addition, it is noted that, for UVCBs, the EC50 or LC50 values actually represent “the loading rate” of the compound and that the true dissolved concentration of the various components may differ. Nonetheless, the toxicological information available is acceptable.

Ecotoxicological effects of the substance BENPAT were studied in several aquatic species including algae, crustaceans, bacteria and fresh water fish. All studies were performed according to OECD guidelines and were described as reliable by the authors of the study (IUCLID Data Set 2003, Study Submission 2010b). While the test substance was first dissolved in acetone before its addition to the test water, solvent controls were included in the study design.

For an algae species, Selenastrum capricornutum, the EC50 values for inhibition of the biomass and growth rate were determined following 72 hour exposure to BENPAT. EC50 values for the test substance were 0.018 mg/L for inhibition of biomass generation and > 0.079 mg/L for inhibition of the growth rate. In addition, the EC10 and No Observed Effect Concentrations (NOEC) were determined to be 0.0043 mg/L and 0.013 mg/L for inhibition of the biomass generation and growth rate, respectively. It should be noted that since statistically significant effects were observed at all test concentrations for the biomass generation parameter, the calculated EC10 value was used to provide an estimate of the NOEC.

Daphnia magna were exposed to BENPAT in an acute immobilization test. The results indicated that the EC50and NOEC values for the test substance were 1.8 mg/L and 0.36 mg/L, respectively. In addition, brown particulates, suggested to be the test substance, were observed to adhere to the test daphnids to the extent that some of the test organisms were buoyed to the surface of the aquaria.

In a more recent toxicity study (Study Submission 2010c), D. magna exhibited a higher sensitivity to BENPAT. Using the acute EC50 value of 1.8 mg/L, exposure concentrations of the test solutions were initially established in the range of 0.26 – 10 mg/L. However, after two days of exposure, these test concentrations caused high D. magna mortalities, so that the study was recommenced using a lower range of exposure concentrations of 0.02 – 0.32 mg/L. This study was carried over 21 days. Using the parameter of fecundity (i.e. live offspring per parent alive at the end of the test period), the 21-day reproduction EC50 value was estimated to be 0.033 mg/L, LOEC value was estimated as 0.007 mg/L, and the NOEC value was less than the lowest concentration tested. Both EC10 and EC20 values were projected from the data generated as 0.0045 mg/L and 0.0090 mg/L, respectively. Moreover, using survival of parent D. magna as a parameter, the 21-day LC50 was calculated as 0.048 mg/L, LOEC was calculated as 0.036 mg/L, and NOEC was calculated as 0.016 mg/L (Study Submission 2010c).

Fresh water fish, rainbow trout and carp, were exposed to BENPAT in a 14 – day test. The resulting LC50 and NOEC values for the rainbow trout were 0.26 mg/L and 0.14 mg/L, respectively. Additional effects in rainbow trout were observed at test substance concentrations exceeding the LC50, including darkened pigmentation of the fish, explained to be likely to due adsorption of the test chemical, lethargic behaviour, loss of equilibrium, as well as effects on body length and weight. LC50 and NOEC values obtained for carp were 0.43 mg/L and 0.28 mg/L, respectively. Additional effects were also observed in the carp at concentrations higher than the LC50, and included darkened pigmentation of the fish, lethargic behaviour and loss of equilibrium.

Finally, toxicity of BENPAT to microorganisms (such as bacteria) was studied in a test for inhibition of oxygen consumption in activated sludge. The observed EC50 value following a 30 minute exposure to the test substance was > 10 000 mg/L.

In addition, cytotoxicity of several antioxidants including representative Structure 1 (or DPPD) was determined in a ciliateTetrahymena pyriformis in a 48-hour photodynamic assay (Epstein et al. 1967). Stock solution of the substance was prepared in acetone. Cultures were incubated in the dark at 28°C; cytotoxicity was established by microscopic examination of culture aliquots. Median LC50 of representative Structure 1 toT. pyriformis was determined to be 0.010 mg/L (Epstein et al. 1967). In the same publication, LC50 values from acute oral toxicity studies of the antioxidant substances to rats were presented. LC50 of representative Structure 1 to rats obtained from an acute oral toxicity study was reported to be in the range of 800 – 1600 mg/kg body weight (Epstein et al. 1967). The authors showed a positive association between toxicity of antioxidants from studies using T. pyriformis and those using rats.

Ecotoxicity of the substance BENTAX was characterized in an MSDS sheet (MSDS 2002a) reporting LC50 and EC50values for several aquatic species. However, it was determined that the ecotoxicity endpoints were actually for a similar material, likely BENPAT, since the test species, the type of test and LC50 and EC50 values were the same as those reported for BENPAT in IUCLID Data Set (2003). Therefore, toxicity information available for the analogue substance BENPATAX (see Table 7) is considered for the substance BENTAX since this analogue contains xylyl derivatives absent from BENPAT (see Table 1a, 1b and 1c for information on substance composition).

Aquatic toxicity of the analogue substance BENPATAX was characterized in several species including algae, crustaceans and fresh water fish (Study Submission 1998). Studies were conducted according to the OECD guidelines. Solvent controls were included in the experimental design.

Toxicity of BENPATAX to algae using S. capricornutmspecies was established in a chronic test where effects on the growth rate and biomass generation were investigated. Based on the algae growth rates observed in the study, the 72-hour EC50 and NOEC values for BENPATAX were 0.11 mg/L and 0.0020 mg/L, respectively. Moreover, the 72-hour EC50for biomass generation was calculated to be 0.0094 mg/L. Similarly, the EC10 was determined to be 0.00075 mg/L and because statistically significant effects were observed on biomass at all treatment levels tested, this value was used as a NOEC estimate for the biomass generation.

Effects of BENPATAX on D. magna were studied in an acute test under flow-through conditions. Resulting 24- and 48-hour EC50 values associated with the observed immobilization of test organisms were > 0.81 mg/L and 0.59 mg/L, respectively. NOEC was established as 0.18 mg/L, based on the absence of immobilization and adverse effects in daphnids following exposure to the test substance. Adverse effects such as lethargy were observed in daphnids exposed to test concentrations lower that the reported EC50 concentrations. Finally, common carp were exposed to BENPATAX in a 14 day test under flow through conditions. LC50 and NOEC values were established as 0.35 mg/L and 0.17 mg/L, respectively. In addition, sub-lethal effects including lethargy and loss of equilibrium were observed in fish exposed to 0.35 mg/L of the substance.

Table 7. Empirical aquatic toxicity data

SubstanceTest organismType of testEndpointValue (mg/L)Reference
BENPATAlgae
(Selenastrum capricornutum)
Chronic
(72 hours)
EC50[1]
(biomass increase)
0.018 (18 µg/L)Study Submission 2010b, IUCLID Data Set 2003
EC50
(growth rate)
> 0.079 (>79 µg/L)
EC10[*]
(biomass increase)
0.0043
(43 µg/L)
NOEC[2]
(growth rate)
0.013
Water flea
(Daphnia magna)
Acute
(48 hours)
EC50
(immobilization)
1.8Study Submission 2010b, IUCLID Data Set 2003
NOEC0.36
Chronic
(21 days)
EC50
(fecundity)
0.033Study Submission 2010c
EC20
(fecundity)
0.0090
EC10
(fecundity)
0.0045
LOEC
(fecundity)
0.007
LC50[3]0.048
LOEC
(survival)
0.036
NOEC
(survival)
0.016
Carp
(Cyprinus carpio)
Acute
(14 day)
LC500.43Study Submission 2010b,
IUCLID Data Set 2003
NOEC0.28
Rainbow trout
(Oncorhynchus mykiss)
Acute
(14 day)
LC500.26
NOEC0.14
Activated sludge (micro-organisms such as bacteria)Acute
(30 minutes)
EC50> 10 000IUCLID Data Set 2003
Structure 1Ciliate
(Tetrahymena pyriformis)
Acute
(48 hours)
IC50[4]0.010
(10 µg/L)
Epstein et al. 1967
BENPATAXAlgae
(Selenastrum capricornutum)
Chronic
(72 hours)
EC50
(biomass increase)
0.0094Study Submission 1998
EC50
(growth rate)
0.11
EC10[*]
(bioamass increase)
0.00075
NOEC
(growth rate)
0.0020
Water flea
(Daphnia magna)
Acute
(24 hours)
EC50>81
Acute
(48 hours)
EC500.59
NOEC0.18
Carp
(Cyprinus carpio)
Acute
(14 day)
LC500.35
NOEC0.17
[1] EC50- The concentration of a substance that is estimated to cause some effect on 50% of the test organisms.
[2] NOEC – The No Observed Effect Concentration is the highest concentration in a toxicity test not causing a statistically significant effect in comparison to the controls.
[3] LC50 – The concentration of a substance that is estimated to be lethal to 50% of the test organisms.
[4] IC50 – The inhibiting concentration for a specified percent effect. A point estimate of the concentration of a test
substance that causes 50% reduction in a quantitative biological measurement such as growth rate.
[*] These EC10 values were chosen as the critical toxicity values (CTV) for the purpose of characterisation of ecological risk. Toxicity studies for BENPAT and BENPATAX to algae S. capricornutum (Study Submission 2010b, 1998) were critically evaluated and the studies were determined to be reliable.

In summary, studies characterizing toxicity of the substance BENPAT and the analogue substance BENPATAX in several aquatic species were available. Although the substance BENPAT can be considered as a read-across substance to BENTAX, it does not include the more methyl-substituted derivative xylyl. Therefore, information available for the substance BENPATAX was considered more relevant and was applied to BENTAX, based on the structural similarities, namely, presence of both tolyl and xylyl derivatives. Additionally, the analogue substance BENPATAX also contains the phenyl derivative, which is not present in BENTAX.

The weight of evidence regarding experimental data for substances BENPAT and BENTAX indicates that both BENPAT and BENTAX are expected to cause acute harm to aquatic organisms at low concentrations (acute LC50s are < 1.0 mg/L).

In addition, studies on the toxicity of tire leachates were reviewed and it was found that rubber antidegradants, including BENPAT, and components of the substance BENPAT and potentially BENTAX, can be detected in the leachates and can contribute to their overall toxicity in the aquatic environment (Wik 2007, OMOEE 1994). The Ontario Ministry of the Environment and Energy (OMOEE 1994) performed chemical analyses and aquatic toxicity tests on tire leachate using several species including Daphnia magna, Ceriodaphnia dubia, rainbow trout and fathead minnow. A Toxicity Identification Evaluation (TIE) was also conducted to identify the substances contributing to the toxicity of the leachate. Test water samples were prepared in batches by submerging a whole automobile tire in water and a batch of water without a submerged tire was used as the negative control. All batches of the test water were acutely toxic to rainbow trout, but toxicity was not observed in all other tested species. The 24- and 96- hour LC50 values for rainbow trout calculated for the first batch of tire water were 58 and 34% vol/vol respectively, and 83 and 52% vol/vol for the second batch (OMOEE 1994).

For the TIE, trout tests were conducted using full strength tire water samples, and the median times to mortality (LT50) were used as the measure of toxicity. Chemical additives (such as hydrochloric acid and sodium hydroxide to determine pH sensitivity, ethylenediaminetetraacetate and sodium thiosulfate to determine if metals were contributing to the observed toxicity) were used to determine characteristics of the toxicants in the tire leachate, and both light sensitivity and persistence of toxicants were also investigated. Finally, addition of the activated carbon to the test samples completely removed the toxicity of the tire leachate to trout indicating that the compound(s) responsible for the toxicity of the tire water are most-likely non-volatile, polar organic compounds (OMOEE 1994).

Test water samples were also analyzed for general water quality parameters (such as hardness, concentrations of organic and inorganic carbon, nitrogen compounds and metals), target organic compounds (including pesticides, chlorinated hydrocarbons, polynuclear aromatic hydrocarbonds, phthalates, amines, etc) and non-target chemicals several of which were arylamines and alkyl phenols that were thought to be degradation products of antioxidant and antiozonant additives . These included Structure 1 (or DPPD), aniline, p-benzoquinone, 2-methyl-N-phenyl-aniline, and N-phenyl-aniline (OMOEE 1994). These components may have been responsible for the observed toxicity, since they are non-volatile organic compounds, however there are several other rubber additives that fit into this class of chemicals, and no link was established between the concentrations of antidegradants in the leachate and toxicity to trout.

In a more recent study, the acute toxicity of BENPAT (referred to as DTPD in this study) in rubber leachates to Daphnia magna was evaluated by Wik (2007), where the toxicity of leachates produced from tire rubber samples that contained various rubber additives (i.e. process and extender oils, antioxidants and antiozonants, vulcanization accelerators, and fillers/reinforcing agents) was assessed.

A typical rubber tire tread was prepared using a minimum number of components and was tested as a reference sample, and rubber samples were prepared by individually adding the different additives to the reference rubber formulation (1.9% BENPAT was added). Tests were conducted by adding cut pieces of the rubber samples to water in the range of 0.31 – 10g rubber/L dilution water, and equilibrated for 72 hours prior to exposure of test organisms. A positive control (K2Cr2O7), and a negative control (dilution water) were used, and both the percentage of immobilized daphnia and EC50 values were calculated for 24 and 48 hour exposure periods. Leachates with the surviving test organisms were subsequently irradiated with ultraviolet (UV) light for 2 hours, and the percentage of immobilized daphnia was recorded 1 hour afterward (Wik 2007).

After 24- and 48-hour exposure to the rubber samples containing BENPAT, the percentages of immobilized daphnia were significantly higher (at 37-42% and 54-56%) than those observed for the reference sample (at 6.3% and 20.6%). Immobility after UV irradiation was also significantly higher in the BENPAT samples than all other samples. The 24 and 48 hour EC50 values for the rubber samples containing BENPAT were 2.5 – 3.3 and 1.4 – 1.5 g rubber/L dilution, respectively. It should be noted that the toxicity reported for the various samples represents the toxicity of the particular additive in addition to the background toxicity of the reference sample (Wik 2007). EC50 values were not calculated for the rubber reference samples due to poor concentration-response relationships.

The highest toxicity to D. magna was observed in rubber samples containing antidegradants, including BENPAT. It is possible that the observed high toxicity was caused by the sequential migration of the antidegradants to the surface of the rubber, where they could leach out more easily. Moreover, toxicity of the rubber samples containing BENPAT increased following UV radiation suggesting that BENPAT could possibly photodegrade into more toxic components (Wik 2007). UV radiation may have also induced degradation of the rubber samples, which in turn increased the leachability of BENPAT. However, non-irradiated samples, which could have been used as controls for increases in toxicity potentially caused by additional leaching of the substance during the last three hours of the test, were not included in the study.

Overall, the study by Wik (2007) indicated that leachates from rubber containing antidegradants such as BENPAT caused toxic effects to D. magna suggesting that these substances could leach out from rubber, and exert toxic effects on aquatic organisms.

In summary, findings from studies on rubber leachates from OMOEE (1994) and Wik (2007) suggest that antidegradants including BENPAT as well as components of the substances BENPAT and BENTAX (such Structure 1, aniline, p-benzoquinone, 2-methyl-N-phenyl-aniline, and N-phenyl-aniline) can potentially leach out of rubber when exposed to water and exert toxic effects in the aquatic environment at relatively low concentrations.

B - In Other Compartments

Toxicity of BENPAT to soil- and sediment-dwelling organisms was investigated under laboratory test conditions (Study Submission 2010c). Soil and sediment studies investigating the effects of BENTAX were not identified.

Soil

Effects of BENPAT on the survival, growth and reproductive capacity of the adult earthworm, Eisenia fetida, were determined. The study was carried out at four test concentrations: 125, 250, 500 and 1000 mg of BENPAT/kg soil dry weight, and using both solvent control (acetone-treated) and untreated controls. Adult earthworms were tested in the treated soil over 28-day exposure period and their offspring was left to develop over the subsequent 28 days. Parameters measured were survival and change in body weight of the adult earthworms after 28 days of exposure and an assessment of the numbers of juvenile worms that had developed by day 56 of exposure.

Following the 28-day exposure period, BENPAT did not cause significant mortality of adult earthworms at the treatment concentrations tested (i.e., 125 – 1000 mg of BENPAT/kg soil dry weight). Effects of exposure to BENPAT on the behaviour, health and biomass of earthworms were not observed. Moreover, no significant effects on the reproductive capacity of earthworms were established. Therefore, the NOEC for BENPAT relating to mortality, change in biomass, behaviour and reproductive capacity of earthworms was found to be the maximum concentration tested or 1000 mg of BENPAT/kg soil dry weight (Study Submission 2010c).

Sediment

Effects of BENPAT in sediment were investigated in a study based on the OECD 218 guideline: Sediment-Water Chironomid Toxicity Test using Spiked Sediment (Study Submission 2010c). The non-biting midge, Chironomus riparius, was used as the animal model. The larvae of C. riparius are tube dwelling suspension and deposit feeders, obtaining nutrition from organic matter in the sediments. Therefore, they tend to come in contact with any sediment-bound contaminants. First instar Chironomids, (i.e., less than three days old) were used in the study. BENPAT was tested at five test concentrations: 25, 64, 160, 400 and 1000 mg/kg dry sediment, and using both solvent (acetone-treated) and untreated controls over a period of 28 days. Sediment test samples were prepared as follows; BENPAT test solutions were added to dry sand, mixed and acetone was evaporated off, and subsequently the spiked dry sand was mixed with the prepared wet sediment.

Both the development time and the total number of fully emerged male and female midges were recorded. The 28-day EC50value of BENPAT to C. riparius was estimated to be greater than 615.2 mg/kg (or 1000mg/kg nominal concentration). The NOEC values for both emergence ratio and the development rate after 28-days were determined to be 615.2 mg/kg (1000mg/kg [nominal concentration]).

Summary

Both soil and sediment studies performed on the earthworm and Chironomids, respectively, showed no effects to the exposure of BENPAT at the maximum concentrations tested.

It is possible that due to its high adsorptive potential, BENPAT is tightly bound to the soil or sediment particles and as a result not bioavailable to the soil and sediment- dwelling organisms. However, given that only one soil and one sediment species were tested thus far, it is also possible that these particular organisms, i.e., the earthworm E. fetida and the non-biting midge C. riparius, do not exhibit high sensitivities to the substance BENPAT.

Ecological Exposure Assessment

Data concerning concentrations of BENPAT and BENTAX in the Canadian environment were not identified. Therefore, environmental concentrations are estimated from available information, including estimated substance quantities, release rates, and size of receiving water bodies. Information regarding the presence of rubber antidegradants such as BENPAT in the environment from tire wear is also summarized.

A – Industrial Release

The aquatic exposure of BENPAT and BENTAX is expected when these substances are released from industrial use to a wastewater treatment plant and the treatment plant discharges its effluent to a receiving water body. The concentration of the substance in the receiving water near the discharge point of the wastewater treatment plant is used as the predicted environmental concentration (PEC) in evaluating the aquatic risk of the substance. It can be calculated using the equation

Cwater-ind = [1000 × Q × L × (1 - R)] / [N × F × D]

where

Cwater-ind: aquatic concentration resulting from industrial releases, mg/L
Q: total substance quantity used annually at an industrial site, kg/yr
L: loss to wastewater, fraction
R: wastewater treatment plant removal rate, fraction
N: number of annual release days, d/yr
F: wastewater treatment plant effluent flow, m3/d
D: receiving water dilution factor, dimensionless

BENPAT

A site-specific exposure analysis was conducted for the aquatic compartment at a total of 3 sites where BENPAT was used as an antiozonant in the production of high durability rubber products. The actual quantity of the substance used at each site was in the overall range of 10 000 to 500 000 kg/yr. Two release scenarios, Scenario 1 and Scenario 2, are presented for each site to capture the range of estimates of the substance loss to wastewater from the production processes from two different information sources.

In release Scenario 1, the estimated fraction lost to wastewater from the production processes is 1% based on OECD (2004c). In release Scenario 2, the estimated fraction lost to wastewater from the production processes is 0.05% based on information provided in Study Submission (2010b). The wastewater containing the substance is then treated by off-site secondary and teritiary (for Sites 2 and 3) wastewater treatment systems with a model predicted removal rate of 48 %. This removal rate was estimated using the wastewater treatment plant removal model ASTreat (2006) based on representative Structure 2, a major component of BENPAT present at approximately 50% of the overall composition of the substance (Huntink et al. 2006). The effluents from these treatment systems are then released to rivers or lakes and a dilution factor limited to a maximum of 10, is used in deriving the predicted environmental concentrations (PECs) from the effluent concentrations. An assumption for the frequency of release of 350 days/year for the 3 sites was also used in the estimation.The PECs estimated for the 3 sites are in the range of 0.8 to 64.82 µg/L for Scenario 1 and 0.04 to 3.24 µg/L for Scenario 2 (Environment Canada 2011a). These PEC values represent the level of exposure in the receiving water near the point of the discharge from the wastewater treatment plant at each site.

Exposure variables used in determining releases of BENPAT from the 3 industrial sites as well as PECs for release Scenarios 1 and 2 are summarised in Table 8a below.

Table 8a. Summary of industrial releases of BENPAT

ScenarioSite 1Site 2Site 3
Scenario 1Scenario 2Scenario 1Scenario 2Scenario 1Scenario 2
PEC (µg/L)12.220.610.80.0464.823.24

BENTAX

A site-specific exposure analysis was conducted for the aquatic compartment at one industrial site where BENTAX was used industrially as an antiozonant in the production of rubber products (Environment Canada, 2011b). The quantity of BENTAX imported for use at this site was reported to be in the range of 100 – 1000 kg (Environment Canada 2010c).

In this site-specific exposure analysis, the industrial site includes one facility, a primary and a secondary wastewater treatment plant and a receiving water body. The predicted environmental concentration (PEC) in the receiving water was estimated based on the concentration in the wastewater treatment effluent and a dilution factor of 10 provided by the receiving water. The fraction released to wastewater was conservatively estimated to be in the range of 2% resulting from the chemical container handling operations and the industrial processes relevant to the facilities under consideration. An assumption for the frequency of release of 24 days/year was also used in the estimation. This assumption is based on estimations of activities relating to the total amount of produced products and the associated use of the substance in batch modes that occur infrequently. The removal rate by a local wastewater treatment plant was estimated by a computer model to be 46.4% (SimpleTreat 1997), based on representative Structure 4, a major component of BENTAX which is expected to be present at approximately 50% of the overall composition of the substance, similarly to representative Structure 2 in BENPAT (Huntink et al. 2006).

Based on the above assumptions, the PEC is estimated to be 0.02 µg/L for the industrial site considered.

Since only the top user was considered in this site-specific analysis along with certain upper bound assumptions, the PEC value obtained is considered to represent the level of exposure under a conservative release scenario in the receiving water near the point of the discharge from the wastewater treatment plant at an industrial site in Canada.

B – Consumer Release

BENPAT use in tires

As BENPAT is found in consumer products including tires and can potentially be released to water, Mega Flush, Environment Canada’s spreadsheet tool was employed to estimate the substance concentration in multiple water bodies receiving wastewater treatment plant effluents to which consumer products containing the substance may have been released (Environment Canada 2009).

This consumer release scenario was not applied to BENTAX, as releases of this substance from consumer products are expected to be very low based on the reported substance use quantities and use patterns (Environment Canada 2005, 2010c).

Mega Flush spreadsheet tool provides estimates for approximately 1000 release sites across Canada based on realistic assumptions. Two Mega Flush release scenarios, Scenario 1 and Scenario 2, were conducted for BENPAT to account for differences in estimations of releases to water and soil. In release Scenario 1, assumptions based on ChemRisk LLC (2009) were used, where releases are distributed at 66% to water and 33% to soil, and of the 66 % water releases, 50% is assumed to be distributed to the sewer and 50 % to other receiving water. In release Scenario 2, a 50/50 % distribution to water and soil is used based on assumptions used in the Mass Flow Tool (see Table 3, Environment Canada 2010a).

The realistic assumptions include.

  • loss to waste water at 0.378% for release Scenario 1 and 0.252% for release Scenario 2,
  • sewage treatment plant removal rate estimated at 0.0 % in case of no treatment,

17 % for primary only treatment and 48 % for primary-secondary combined treatment.

  • number of annual release days at 365 days/year,
  • receiving water dilution factor in the range of 1 to 10.
  • 12% of rubber released from rubber particles due to abrasion (ChemRisk LLC 2009)
  • 6.3% of BENPAT leaching out of rubber particles into water[4]

The predicted environmental concentration (PEC) of BENPAT in the receiving water bodies was estimated to be in the range of 7.4x10-6 to 2.2x10-3 mg/L. The estimate is based on a total substance quantity assessed to be used in tires. The equation and inputs used to calculate the PEC are described in Environment Canada (2011c, d ).

Additional information on tire wear

Additional information regarding the presence of rubber antidegradants such as BENPAT in the environment from tire wear is summarized below.

Tire wear particles are released from the tire tread as a result of the interaction between the tire and the pavement (ChemRisk 2008). Most of the abraded rubber is released as relatively large particles that deposit on the sides of roads, whereas less than 5% of particles are airborne and less than 1% of abraded rubber is released as gaseous emissions. Particles deposited on the sides of road can subsequently make their way into aquatic environments through road runoffs (Wik and Dave 2009). Estimates based on 1970 data indicated that approximately 30% of tread rubber from tires is worn off and released to the environment (Wik and Dave 2009). More recent estimates point to lower environmental releases of tread rubber, in the range of 10 – 12% (Camatini et al,

2001, Blok 2005, OECD 2004c, ChemRisk LLC 2009). Historical estimates of tread rates from the 1970s are higher because modern radial tires are characterized by a lower wear rate than the bias ply tyres used in the earlier time period (Veith 1992). Antiozonants typically make up about 1% of tread rubber (Wik and Dave 2009). Elsewhere, it was reported that antiozonants may be present in rubber in a range of 0.25 – 4 % and up to 8% by weight (Goodyear Tire and Rubber Company 1965).

A multi-year research program to address the potential environmental, health, and ecological impacts associated with tire wear particles was undertaken by the Tire Industry Project Group (TIPG), working through the World Business Council on Sustainable Development, and including several industry members (ChemRisk 2008). Information to date includes studies addressing roadway particle composition, including both organic and inorganic substances, as well as their environmental leaching potential. Available findings have been summarized in reports (ChemRisk 2008, ChemRisk and DIK 2008), published in peer-reviewed literature (Kreider et al. 2010) and presented at a conference (MacAtee et al. 2010).

Three types of particles originating from tire wear were identified and their composition and physical properties were analysed in a study undertaken by the TIPG (ChemRisk 2008). Roadway particles (RP) are composed of a mixture of elements from tires, pavements, fuels, breaks and road dust. Tire Wear Particles (TWP) are produced by the interaction between tires and pavement. Tire Particles (TP) are composed of pure tire tread. The overall chemical composition varies for these three types of particles and their size and physical shapes also exhibit differences (ChemRisk 2008, Kreider et al. 2010). For instance, RPs and laboratory generated TWP have a similar elongated cigar-shape, the TPs are larger and have more jagged edges.

For this study, tire particles were generated in a laboratory setting and collected from typical passenger and truck tires using a specifically designed on-road collection system. Road-generated and laboratory particles were similar in elemental composition and contained a similar amount of rubber.

Analyses of the organic components of RPs and laboratory generated TWPs revealed the presence of antioxidants including BENPAT (referred to as DTPD in the report) at concentrations in parts per million (ppm) (ChemRisk 2008). Moreover, an acetone extraction was performed to identify components of RPs and TPs that have a potential to leach. Several antioxidants were found in the acetone extracts of both RPs and TPs along with several other organic chemicals such as components of oils and waxes, and phthalates (ChemRisk 2008). BENPAT was detected in the acetone extraction from TPs (MacAfee et al. 2010).

The leaching potential of the chemicals identified in the acetone extractions was tested where the RPs and TP were leached in simulated rainwater. Rain water at pH 7.5was dripped for 16 hours onto columns containing RPs or TPs. The water was then collected and tested for organic chemicals and metals. Organic chemicals were not detected in the water leachate after 16 hours, except formaldehyde (ChemRisk 2008). Leaching of chemicals from RPs that have been mixed with soil, as may occur along a roadside, was also simulated in a similar manner to the water column studies for the period of 16 hours. The soil leachate water was collected and analyzed. Organic chemicals including antiozonants were not present in the soil leachate.

These 16-hour studies, simulating a single rainfall event, on the leaching potential of organic tire additives including BENPAT, indicated lack of presence of such substances in the leachates (ChemRisk 2008). However, given the very short duration of these studies, lack of variation in experimental conditions and a strong adsorptivity potential of BENPAT, the leaching potential of this substance may not be fully captured. Indeed, these studies do not illustrate longer-term environmental conditions and associated effects on the leaching potential of antiozonants such as BENPAT from tire wear particles.

In other studies, dating back to the 1970s, estimates of tread rubber emissions from tires based on different tire markers have been reported (Wik and Dave 2009). Tire markers provide a feasible way to monitor tire wear particle concentrations in the environment. Soil, sediment and airborne tire wear fractions cannot be determined from measured or theoretically derived tire wear rates (ChemRisk and DIK 2008). Data on releases of rubber tire particles to the environment for selected European countries, Japan and the US were summarized by Wik and Dave (2009). Concentrations of rubber particles in the environment were estimated based on tire markers, i.e. measured concentrations of common rubber components and additives including styrene butadiene rubber (SBR), natural rubber (NR), benzothiazoles (HOBT and 24MoBT) and organic zinc (Wik and Dave 2009). The use of antiozonants as tire markers has not been documented, presumably because antiozonants are chemically reactive rubber additive materials (ChemRisk and DIK 2008). However, chemical analyses of tire tread particles revealed that they contain antidegradent substances (ChemRisk 2008).

It should be noted that the use of tire markers can lead to both overestimation and underestimation of tire particle concentrations, as the markers could be subject to degradation in the environment, or they could have other sources of releases to the environment in addition to tires (Wik and Dave 2009). Further description of reliability of the different tire markers, including various polymer based markers, benzothiazole (BT) and 2-(4-morpholinyl)benzothiazole (24MoBT), N-Cyclohexyl-2-benzothiazolamine (NCBA), zinc based markers, and high-boiling additive based markers present in styrene butadiene rubber (SBR), was presented in the report by ChemRisk and DIK (2008). It was concluded that tire markers with the most potential for use were the polymer based pyrolysis markers (isoprene, butadiene and thiophenes) and the organic zinc.

Estimated environmental concentrations of tire particles from the Wik and Dave (2009) study are summarized for the US only and presented in Table 8b. In the US, annual releases of tire rubber particles to the environment are approximately 500 million kg. Concentrations of tire particles in road dust were estimated to be in the range of 0.7 to 210 g/kg dw based on the highest measured concentrations of different tire markers. In soils alongside roads, 0.6 – 117 g/kg dw were estimated based on the highest measured concentrations of different tire markers. The concentrations of tire particles in road dust and soil decreased with distance from the roads. Tire tread particles could also be applied to agricultural soils as a component of sludge from wastewater treatment plants (WWTPs). It has been estimated that approximately 16% of zinc from WWTPs originates from tire wear, and zinc concentrations in WWTP sludge have been measured to be as high as 4g/kg dw. Assuming zinc makes up approximately 1.5% of tread rubber, the concentration of rubber tire particles in WWTP sludge was estimated to be 42.7 g/kg dw (Wik and Dave 2009).

Based on concentrations of benzothiazoles, tire wear particle concentrations in road runoff were estimated to range from 0.3 to 197 mg/L. Comparatively low concentrations of tire particles were estimated in receiving waters. Based on the road runoff values, tire particle concentrations of 0.03 to 17.9 mg/L were estimated to be found in receiving waters. Concentrations of 0.09 to 6.4 mg/L were obtained based on measured concentrations of benzothiazoles (Wik and Dave 2009). Concentrations of tire particles in sediment were estimated to range from 0.3 to 155 g/kg dw based on measured concentrations of benzothiazoles and zinc. However, since the benzothiazole compounds are soluble in water and do not tend to accumulate in sediment, this marker likely underestimates the concentration of tire particles found in sediment (Wik and Dave 2009). Concentrations of tire particles in ambient air along roadways are estimated to range from 0.4 to11 µg/m3.

Table 8b. Estimated environmental concentrations of tire particles

MediumLocation; yearTire markerReference[1]Estimated environmental concentrations of tire particles[2]
AirAkron Expressway, Ohio, USA; 1973; Allegheny Mountain Tunnel, Pennsylvania, USA; 1973SBR[4]Cardina 1974; Pierson and Brachaczek 19746-11 µg/m[3]
San Gabriel River Freeway, California, USA; 1974SBR[4]/NR[5]Cadle and Williams 19780.5 µg/m[3]
Road runoffPawtuxet, Woonasquatucket, and Moshassuck Rivers, Rhode Island , USA; 1995HOBT[6]Reddy and Quinn 199787 mg/L
Ballona Creek and Santa Ana River, California, USA; 1997-199824MoBT[7]Zeng et al. 200492 mg/L
River waterhighway-settling pond (intersection of RI Routes 102 and 4) and the Pawtuxet River, Rhode Island, USA; 199524MoBTReddy and Quinn 19971.6 mg/L
SedimentSan Francisco Bay, California, USA24MoBTSpies et al. 1987155000 mg/kg dw
highway settling-pond, Pawtuxet River, and Narragansett Bay, Rhode Island, USA; 1995HOBTReddy and Quinn 1997400 mg/kg dw
SoilSan Gabriel River Freeway, California, USA; 1974; Rotunda Drive, Michigan, USA; 1973 (0m from road)SBRCadle and Williams 1978; Pierson and Brachaczek 19744500-24000 mg/kg dw
Highway 80, Berkeley, California, USA (0m from road)24MoBTSpies et al. 1987117000 mg/kg dw
Rotunda Drive, Michigan, USA; 1973 (8m from road)SBRPierson and Brachaczek 19741000 mg/kg dw
San Gabriel River Freeway, California, USA; 1974 (30m from road)SBRCadle and Williams 19780 mg/kg dw
dw = dry weight; OC = organic carbon
[1] Studies that report measured environmental tire marker concentrations that were used by Wik and Dave (2009) in the estimation of tire particles in the environment
[2] estimated by Wik and Dave (2009)
[3] Calculated antidegradent concentrations based on reported estimates of tire particles, assuming 1% antidegradent in the tire tread rubber (Wik and Dave 2009)
[4] SBR: styrene butadiene rubber
[5] NR: natural rubber
[6] HOBT: 2-hydroxybenzothiazole
[7] 24MoBT: 2-(4-morpholinyl)benzothiazole

In summary, the Wik and Dave (2009) study illustrated that particles from tire treads are released into the environment. Tire tread particles contain antidegradent substances like BENPAT; such substances are added to tires as protective agents (Kirk-Othmer c2010, Iatropoulos et al. 1997).

Finally, bioavailability of antiozonants from tire particles is not well addressed at the present. Reliable studies on bioavailability of antioxidants from tire wear particles were not identified; however bioavailability of tire antidegradants from whole tire leachate was demonstrated in a study by Stephensen et al. (2003). In the Stephensen et al. (2003) study, four antidegradants or metabolites of antidegradants, other than BENPAT, were measured in bile of rainbow trout after exposure to water containing whole tire leachate. It is possible that BENPAT was not present in the rubber samples tested by Stephensen et al. (2003), however some of the antiozonant compounds measured were structurally similar. For example, a compound measured, N-(1-methylethyl)-N’-phenyl-1,4-benzenediamine (IPPD), differed from the representative Structure 1 of BENPAT by the presence of an alkyl group instead of an aryl group.

Lastly, several studies on bioavailability of tire wear particles were summarized in Wik and Dave (2009), and overall, the results indicated that tire wear particles may be bioavailable to pelagic filter-feeding organisms, to benthic organisms and to plants.

Characterization of Ecological Risk

The approach taken in this ecological screening assessment was to examine various supporting information and develop conclusions based on a weight-of-evidence approach and using precaution as required under CEPA 1999. Lines of evidence considered include results from risk quotient calculations, as well as information on persistence, bioaccumulation, toxicity, sources and fate of the substance.

Components of BENPAT and BENTAX are expected to be persistent in water, soil and sediment; major components of both BENPAT and BENTAX are also expected to have a moderate to high bioaccumulation potential. Components of BENPAT and BENTAX meet the criteria for persistence, but not bioaccumulation potential as set out in thePersistence and Bioaccumulation Regulations (Canada 2000). Once released into the environment, both BENPAT and BENTAX may be found in water, soil as well as sediment. BENPAT and BENTAX have also been demonstrated to have a high potential for toxicity to aquatic organisms.

Substances that are persistent remain in the environment for a long time after being released, increasing the potential magnitude and duration of exposure. Substances that have long half-lives in mobile media (such as water) and partition into these media in significant proportions have the potential to cause widespread contamination. Releases of small amounts of bioaccumulative substances may lead to high internal concentrations in exposed organisms.

BENPAT

A risk quotient analysis, integrating estimates of exposure with toxicity information, was performed for the aquatic medium to determine whether there is potential for ecological harm in Canada. The site-specific industrial scenarios (considering the actual receiving water bodies) presented above yielded a predicted environmental concentration (PEC) in the range of the range of 0.8 to 64.82 µg/L for Scenario 1 and 0.04 to 3.24 µg/L for Scenario 2 (Environment Canada 2011a). A predicted no-effect concentration (PNEC) for BENPAT was derived from the chronic toxicity value of 0.0043 mg/L (as the most sensitive experimental value, see Table 7) for algae, S. capricornutum, by dividing this value by an assessment factor of 10 (to account for interspecies and intraspecies variability in sensitivity and to extrapolate from laboratory to field conditions) to give a value of 0.00043 mg/L (or 0.43 µg/L). The resulting risk quotients (PEC/PNEC) for BENPAT resulting from release Scenario 1 are in the range of 1.9 – 150.7 and in the range of 0.1 – 7.5 for Scenario 2. They are summarized in Table 8c below.

Table 8c. Risk quotients for BENPAT obtained from industrial release scenarios

ScenarioSite 1Site 2Site 3
Scenario 1Scenario 2Scenario 1Scenario 2Scenario 1Scenario 2
PEC (µg/L)12.220.610.80.0464.823.24
RQ28.41.41.90.1150.77.5

Using a similar PEC/PNEC approach, the consumer release spreadsheet tool (Mega Flush) predicted in the first scenario considered (Scenario1), that PECs for BENPAT may exceed the PNEC in about 4% of the water bodies receiving wastewater across Canada under low (10th percentile) flow conditions (Environment Canada 2011c). Predictions from the second scenario (Scenario 2) were higher, where about 11% of the water bodies receiving wastewater across Canada under low (10th percentile) flow conditions (Environment Canada 2011d). The maximum PEC/PNEC calculated from Mega Flush release Scenario 1 was 3.7 and the maximum RQ calculated from Mega Flush release Scenario 2 was 5.1 (Environment Canada 2011c, d).

The information indicates that BENPAT has the potential to cause ecological harm in Canada.

BENTAX

A risk quotient analysis, integrating conservative estimates of exposure with toxicity information, was performed for the aquatic medium to determine whether there is potential for ecological harm in Canada. The site-specific industrial scenario (considering the actual receiving water body) yielded a predicted environmental concentration (PEC) of 0.0036 µg/L (Environment Canada 2011b). A predicted no-effect concentration (PNEC) was derived from the acute toxicity value of 0.00075 mg/L as the most sensitive valid experimental value available for the analog substance BENPATAX for algae, S. capricornutum (see Table 7), and by dividing this value by an assessment factor of 10 (to account for interspecies and intraspecies variability and extrapolation from laboratory to field conditions) to give a value of 0.000075 mg/L (or 0.075 µg/L). The resulting risk quotient (PEC/PNEC) = 0.047. Therefore, harm to aquatic organisms is unlikely due to the limited industrial use and release quantities of the substance.

Overall, this information suggests that BENTAX is unlikely to be causing ecological harm in Canada.

Uncertainties in Evaluation of Ecological Risk

All modelling of a substance’s physical and chemical properties and persistence and bioaccumulation characteristics are based on chemical structures. As substances BENPAT and BENTAX are UVCBs (Unknown or Variable composition, Complex reaction product or Biological materials), they cannot be represented by single, discrete chemical structures. Therefore, for the purposes of modelling, “representative structures”, i.e. representative Structures 1 – 5 were identified to provide conservative estimates. These structures represent the major components that make up BENPAT and BENTAX. Given that several representative structures may be derived for the same UVCB, it is recognized that structure-related uncertainties exist for these substances. For instance, while the proportion of the various representative structures can be estimated or measured, these proportions may vary between batches of the imported substance. Also minor components of BENPAT and BENTAX that are present in the mixtures in less than 5 % were not considered in the present assessment.

Some of the available experimental physico- chemical properties of BENPAT were reported as ranges (see Tables 2a and b), therefore there is variability in those results. When such properties were used for input into models, this variability was translated into the model outputs that potentially either over- or under-estimated the true values. When ranges of values were available for physico-chemical endpoints, models were run for both the highest and the lowest values of the ranges to infer into the possible extent of outputs.

There is uncertainty regarding the experimental evaluation of water solubility of BENPAT as well as the analogue substance BENPATAX. The water solubilities of individual major components and minor components of BENPAT and BENPATAX were established experimentally. Water solubilities of the major components were a magnitude lower that those of the minor components, and still lower than the overall water solubilities established for each substance. It is unclear how the overall water solubility values of BENPAT and BENTAX were estimated and consequently how accurate these values are. Since water solubility is one of key parameters to the general understanding of the behaviour and fate of a substance in the environment, and in fugacity modelling, it is important that such estimates are reliable.

It is noted that environmental exposure stemming from BENPAT present in recycled rubber products, including those used in recreational areas such as playgrounds and sports fields, is not addressed in this screening assessment. Information regarding potential environmental releases from recycled products containing BENPAT and potentially BENTAX is presently not available in the published literature and unpublished sources. As such, any potential releases to the environmental media are unknown at the present time.

With regards to the bioaccumulation data for the representative Structure 3 of BENPAT and BENTAX, there is uncertainty associated with the available empirical results. Based on a careful analysis of metabolic rates, depuration rates and consideration of the variability encountered in the available fish study, it is believed that the results for the representative Structure 3 do not constitute sufficient and consistent evidence that it meets the bioaccumulation criterion (BCF or BAF > 5000) as set out in thePersistence and Bioaccumulation Regulations (Canada 2000); however, this major component of BENPAT is believed to have a significant potential to bioaccumulate. Additional bioaccumulation experimental data for BENPAT is therefore desirable to confirm the analysis of bioaccumulation potential. Structure 3 is also partially representative of BENTAX, with the expected distribution similar to that found in BENPAT, at approximately 25%. Experimental bioaccumulation data, including an in vivo aquatic bioaccumulation study, for the substance BENTAX is not currently available. Such data, and in particular fish BCF values for the representative Structures 3, 4 and 5 of BENTAX, which are analogous to those determined for the representative Structures 1, 2 and 3 of BENPAT, are important and valuable. These data could also be applied to inform and evaluate experimental results obtained for BENPAT and its representative Structure 3.

When BENPAT is released into a water body, it tends to partition into suspended particulate matter and to bottom sediments, where sediment-dwelling organisms could be exposed to the substance. No environmental monitoring data are presently available for this substance. Ecotoxicological data specific to a single sediment-dwelling organism, the non-biting midge, C. riparius, indicated no toxicity (Study Submission 2010c). Based on the data available, it is uncertain whether bioavailability of sediment-adsorbed BENPAT is limited or whether the non-biting midge exhibits low sensitivity to this substance. Given the high toxicity of the substance to a number of aquatic species tested (see Table 7), it is difficult to indicate with certainty that harm to sediment-dwelling organisms in Canada is unlikely.

Given that BENTAX, similarly to BENPAT, tends to partition into suspended particulate matter and to bottom sediments, sediment-dwelling organisms could be exposed to the substance. Ecotoxicological data established for sediment-dwelling organisms was not available for BENTAX; however data obtained for BENPAT (Study Submission 2010c) can be used as read-across for this substance based on similar structural and property characteristics of these substances. Given the uncertainties associated with availability of the toxicity profile to only one species, the non-biting midge, C. riparius, it is difficult to predict the degree of effects for other sediment-dwelling organisms. Based on the risk quotient analysis for the industrial site where BENTAX is used and assuming that the level of sensitivity to the substance is similar to that of the aquatic species, harm to sediment-dwelling organisms is unlikely.

Potential to Cause Harm to Human Health

Exposure Assessment

Environmental Media and Food

Based on their use patterns, BENTAX and BENPAT are not expected to be found in food or beverages in Canada.

Empirical data on concentrations of BENTAX and BENPAT in environmental media in Canada were not identified. Environmental concentrations were estimated using ChemCAN v6.00, a Canada-specific far-field level III fugacity model that estimates environmental concentrations on a regional scale due to annual releases of a substance (ChemCAN 2003). Annual releases of BENTAX and BENPAT were conservatively estimated using the upper bound of the total quantity in commerce in 2006, namely 1 000 kg and 10 000 000 kg, respectively, and the loss percentages predicted by the Mass Flow Tool for industrial, commercial and consumer use (see Table 3) (Environment Canada 2010a, b, c). The loss percentages are not considered to be releases to the environment; however, they were used as worst-case estimates for the purposes of modelling. Loss quantity estimations are provided in Appendix III.

The environmental concentrations estimated by ChemCAN v6.00 are also presented in Appendix III. Conservative upper-bounding daily intakes of BENTAX and BENPAT for the general population in Canada were derived based on the estimated environmental concentrations. Negligible environmental exposure to BENTAX in the order of 10-1 nanograms (10-10 g) per kg-bw (kilogram of body weight) per day was estimated. Total estimated environmental exposure to BENPAT ranged from 0.06 – 0.63 µg/kg-bw per day for various age groups and was highest for formula-fed infants (0-6 months) (see Appendix IV).

BENPAT and BENTAX are used as additives to prevent degradation in high durability rubber. BENPAT specifically may be used in tire rubber. Release of tire particles from tire wear could therefore represent a potential source of exposure for the general population, especially along transportation corridors. However, the potential for inhalation exposure to BENPAT is expected to be low as almost all roadway particles (containing approximately 15% tire material), generated under realistic outdoor driving conditions, are greater in size than the respirable cutoff diameter (10 µm) (Kreider et al. 2010). In addition, while there may be some dispersion of these tire particles to adjacent soil, the dispersive tendency is considered minimal as a reduction of tire particle concentrations of greater than 80% has been observed within 30 m of a road (Wik and Dave 2009).

Consumer Products

As discussed above, BENTAX and BENPAT are used as additives to prevent degradation in highly durable rubber. In the class of diaryl para-phenylenediamines, these substances may be used as rubber antiozonants and antioxidants (TradingChem 2008, PCP 2008).

BENPAT is present as an antiozonant in some rubber compounds at a reported concentration of 0.29 to 2.17% by weight (Environment Canada 2010c). In tread rubber from tires, the typical concentration of antiozonants is 1% by weight (Wik and Dave 2009). Elsewhere, it was reported that antiozonants are present in rubber at a range of 0.25 – 4% and up to 8% by weight (Goodyear Tire and Rubber Company 1965). In general, BENPAT is used as an antioxidant for chloroprene rubber and in the tire and industrial belt industries (PCP 2008). As BENPAT is a rubber additive mixed within the polymer matrix of rubber at low concentrations, any incidental dermal contact with tires by consumers is not expected to result in dermal exposure.

Uses for BENTAX, in response to a notice issued under section 71 of CEPA 1999, were reported as confidential business information and cannot be disclosed. However, based on its use as a moderately active antiozonant at low concentrations with poor water solubility, any exposure to rubber products is anticipated to be incidental to negligible (Kirk-Othmer c2010).

Health Effects Assessment

Available health effects information for BENPAT and BENTAX are summarized in Appendix V. Health effects data on the analogue BENPATAX were also considered to further inform the assessment of health effects of BENPAT, and are summarized in Appendix V. The structures and identities of these substances are presented in Table 1 of the Substance Identity section.

Australia’s National Industrial Chemicals Notification and Assessment Scheme (NICNAS) conducted a risk assessment of BENPATAX (NICNAS 2001). No national or international assessments were identified for BENPAT or BENTAX specifically.

No carcinogenic effects were observed in a 52-week oral study in Fischer 344 rats exposed to BENPAT at doses up to 95 mg/kg-bw per day (AHF 1996c, Iatropoulos et al. 1997). Although significant increases in urothelial cell proliferation and hyperplasia were observed in all BENPAT treated groups, no neoplasia was observed. The absence of tumour initiating or promoting activity in liver and urinary bladder of male Fischer 344 rats was also confirmed in a 38-week accelerated bioassay (at a dose of 95 mg/kg-bw per day) (AHF 1996b; Iatropoulos et al. 1997). Similarly, no carcinogenic effects were reported in a 52-week oral toxicity study in rats exposed to the analogue BENPATAX at doses up to 100 mg/kg-bw per day (Iatropoulos et al. 2000).

The potential genotoxicity of BENPAT, BENTAX or BENPATAX has been assessed in several in vitro and in vivoassays. There was no indication of genotoxicity in any of thein vivo tests, which included a mouse bone marrow micronucleus assay and two mutagenicity assays inDrosophila spp. (AHF 1995; ECB 2003; Goodyear Tire and Rubber Company 1992a, c; Litton Bionetics 1979; Pharmakon 1993a). Most of the in vitro tests in both bacterial and mammalian cell systems were negative (AHF 1999, Crebelli et al. 1985; ECB 2000, 2003; Jeffrey 1999; SanSebastian 1994). Weak positive responses in some Salmonella strains in the presence of metabolic activation, were observed with all three compounds (ECB 2003, Stankowski 1998, Goodyear Tire and Rubber Company 1992 a, c, d). Positive results were also observed in DNA damage and repair assays with Escherichia coli for BENPAT and BENTAX in the absence of metabolic activation (assays were not conducted with metabolic activation) (ECB 2003, Goodyear Tire and Rubber Company 1992a, c, d). Consideration of the above mentioned available information indicates that BENPAT and BENTAX are not likely to be genotoxic.

In a two-generation reproductive toxicity study, Sprague-Dawley rats were orally exposed to 0 to 75 mg/kg-bw per day of BENPAT from 10 weeks premating through to the weaning period of pups (21 days). Significantly prolonged gestation periods were observed in dams at 20 and 75 mg/kg-bw per day for F0 dams and at all dose levels for F1 dams. Significant increases in post implantation loss and decreases in total and live pups were seen in the F1 and F2 litters at 20 and 75 mg/kg-bw per day. Dystocia and delayed parturition were also observed at these doses in the study. Polycystic lesions in the kidneys with dose-related incidence and severity were reported at all dose levels (6, 20 and 75 mg/kg-bw per day) in F0 and F1 parents and in F1 and F2 weanlings. However, there was no evidence of male reproductive toxicity reported (Goodyear Tire and Rubber Company 2001). A mechanistic study was also performed in the same strain of rats at an oral dose of 125 mg/kg bw/day, to further investigate the association of exposure stages versus the health effect observed in the above mentioned two-generation study. The results confirmed that exposure to BENPAT during the gestational period resulted in dystocia and delayed parturition, and also resulted in polycystic kidneys in F1 offspring. Pre-gestational exposure did not enhance the effects attributed to BENPAT ingestion during the gestation period (Goodyear Tire and Rubber Company 2001).

In two developmental toxicity studies, female Sprague-Dawley rats were exposed by gavage to BENPAT or BENPATAX for 10 days during gestation. Reduced body weights in foetuses and dams (associated with reduced food consumption) were observed at 200 mg/kg-bw per day for BENPAT (highest dose tested) and at 70 and 200 mg/kg-bw per day for BENPATAX. No compound-related abnormalities (malformations or variations) were observed in offsprings (ECB 2003; Tyl 1996).

With regards to non-cancer effects, a significant increase in urothelial cell proliferation and hyperplasia were observed at all doses tested in both genders of Fischer 344 rats orally exposed to BENPAT at doses of 0 to 95 mg/kg-bw per day for 52 weeks (Iatropoulos 1997). Increases in relative organ weights (liver, spleen, heart and kidney) and decreases in body weight gain and food consumption were also observed in high-dose rats. Similarly, an increase in urothelial cell proliferation in the bladder, decreased body weights and increased organ weights (at 30 and 120 mg/kg-bw per day) were also reported in the same strain of rats in a 28-day oral study with BENPAT (AHF 1996a). Oral administration of BENPATAX for 4 weeks resulted in hyperplasia of the urothelium and increased urothelial cell proliferation in high-dose Fischer 344 rats (100 mg/kg-bw per day) (Iatropoulos et al. 1998; NICNAS 2001).

Hematological effects due to oral exposure of BENPAT were also observed in several chronic and short term toxicity studies in Fischer 344 rats. Signs of macrocytic anemia, including reversible increases in mean corpuscular volumes (MCV) and decreases in mean corpuscular hemoglobin concentration (MCHC), as well as clinical chemistry changes (increased blood bilirubin and cholesterol levels) were observed in both sexes of high-dose (120 mg/kg-bw) rats in a 28-day study with BENPAT (AHF 1996a). Significantly increased MCV, decreased MCHC and red blood cell count accompanied by microscopic evidence of extramedullary erythropoiesis in the spleen and liver were also observed at 95 mg/kg-bw per day (highest dose tested) in a 52-week study. Increased bilirubin and cholesterol and decreased total protein levels were also reported in high dose rats (AHF 1996c, Iatropoulos et al. 1997). The same results were confirmed by a 38-week accelerated oral bioassay in rats exposed to BENPAT at 95 mg/kg bw/day (Iatropoulos et al. 1997). Similar hematopoietic effects were also observed in a 52-week study in rats exposed to the analogue, BENPATAX. At 20 and 100 mg/kg-bw per day. histopathological changes in the spleen, liver, kidney and bladder in high dose animals provided further evidence of macrocytic anemia (Iatropoulos et al. 2000, NICNAS 2001). Signs of macrocytic anemia were also reported in the 28-day study in rats exposed to BENPATAX at 120 mg/kg-bw per day (Iatropoulos et al. 1998).

The chronic oral lowest observed adverse effect levels (LOAELs) ranged from 2.7 mg/kg-bw per day (lowest tested dose) for BENPAT in rats, based on significant increases in urothelial cell proliferation and hyperplasia (AHF 1996c), to 20 mg/kg-bw per day for BENPATAX in rats, based on macrocytic anemia (Iatropoulos et al. 2000). The lowest oral short-term LOAELs identified ranged from 30 mg/kg-bw per day for BENPAT in rats, based on increased urothelial cell proliferation in the bladder (AHF 1996a), to 120 mg/kg-bw per day for BENPAT and BENPATAX in rats, based on macrocytic anemia (AHF 1996a, Iatropoulos et al. 1998). In a developmental oral toxicity study in rats, a developmental LOAEL of 20 mg/kg-bw per day, based on prolonged gestation length, increased post implantation loss, and decreased number of total pups and live pups, and a systemic LOAEL of 6 mg/kg-bw per day, based on polycystic lesions in the kidneys, were determined (Goodyear Tire and Rubber Company 2001).

The results from acute toxicity studies indicated that the oral LD50 values in rats for BENPAT, BENTAX and the analogue BENPATAX and the dermal LD50 values in rabbits for BENPAT and BENPATAX were all greater than 2000 mg/kg-bw following a single exposure (Bayer 1990, ECB 2003, Pharmakon 1993b, The Goodyear Tire and Rubber Company 1992b, WARF 1959, Merriman 1995a, b, Springborn Laboratories 1995a). No acute inhalation studies were identified. Mixed results were observed in skin and eye irritation studies in rabbits exposed to BENPAT (Bayer 1991, Springborn Laboratories 1995b, WARF 1959). BENPAT was considered to be a skin sensitizer based on weak sensitization responses observed in a maximization test in guinea pigs (Springborn Laboratories 1995c). Similar sensitization responses were observed in guinea pigs with the analogue BENPATAX (Merriman 1995d). BENPATAX also demonstrated slight to moderate irritation to the skin of rabbits (Merriman 1995b, c).

Confidence in the Health Effects Database

The confidence in the toxicity database of BENPAT is considered to be moderate as empirical data were identified. However, no repeated dose dermal or inhalation toxicity studies were identified for BENPAT nor for BENTAX (or BENPATAX). Although repeated dose oral toxicity and reproductive/developmental toxicity studies were not identified for BENTAX specifically, read-across from BENPAT and BENPATAX databases increased confidence in determining the potential health effects of BENTAX. Thus, the confidence in the toxicity database for BENTAX is low to moderate.

Characterization of Risk to Human Health

No evidence of carcinogenicity was observed in several chronic oral studies in rats exposed to BENPAT and the analogue BENPATAX. Available information indicates that BENPAT, BENTAX and BENPATAX are not likely to be genotoxic. Therefore, characterization of risk in this assessment is based on non-cancer effects of BENPAT and BENTAX.

Empirical health effects data identified for BENPAT, BENTAX and BENPATAX indicate a low potential for acute hazard by the oral and dermal routes. The target organs following repeated oral exposure to BENPAT and BENPATAX were consistently the urinary and hematopoietic systems. The lowest observed adverse effect level was determined to be 2.7 mg/kg-bw per day of BENPAT, based on a significant increase of urothelial cell proliferation and hyperplasia in rats. The lowest concentration at which adverse hematological changes (increased MCV, decreased MCHC and red blood cell count) were observed was 20 mg/kg-bw per day with BENPATAX administered orally to rats; these effects were also reported in other short-term and chronic studies conducted with BENPAT and BENPATAX at doses of 95 and 120 mg/kg-bw per day.

Critical effects included reproductive and developmental effects. Prolonged gestational lengths for F1 dams and polycystic lesions in kidneys of F1 and F2 weanlings were observed in rats exposed to 6 mg/kg-bw per day (LOAEL) of BENPAT in a reproductive and developmental toxicity study. Repeated oral exposure of BENPAT at 20 mg/kg-bw per day resulted in reproductive impairment in dams, including dystocia, increased post implantation loss, decreased total and live pups numbers, and delayed parturition.

Environmental exposure to BENTAX was estimated to be in the order of nanograms (10-9 mg) per kg-bw per day, and therefore was considered to be negligible. Maximum estimated environmental exposure to BENPAT was 0.63 µg/kg-bw per day (see Appendix IV). The potential for exposure of the general population to BENPAT and BENTAX in consumer products is considered to be negligible as incidental dermal contact with rubber products is not expected to result in dermal exposure.

A comparison between the critical effect levels for repeated dose oral exposure (2.7, 6 and 20 mg/kg-bw per day) to the upper-bounding estimates of exposure from all sources of environmental exposure to BENPAT (0.06 - 0.63 µg/kg bw/day) results in margins of exposure (MOEs) of approximately 4 285 to 333 300 (see Appendix VI for details). These margins are considered adequate to account for uncertainties in the health effects and exposure databases.

Uncertainties in Evaluation of Risk to Human Health

Confidence in the estimates of exposure to BENPAT and BENTAX of the general population from environmental media is low. Data in the literature were not identified for concentrations of these substances in environmental media. Maximum values of quantities in commerce were combined with the Mass Flow Tool percentages for the ChemCAN model; therefore, it is likely that modeled estimates of environmental exposure are conservative. The commercial uses identified for BENTAX and BENPAT in literature searches and in responses to a notice issued under section 71 of CEPA 1999, namely as antiozonant and antioxidant agents in rubber products, are not expected to result in exposure of the general population.

There is some uncertainty with regards to exposure to BENPAT and BENTAX from consumer products; however, available sources of information indicate that exposure of the general population from consumer products is unlikely. There is also some uncertainty related to potential secondary uses of tires however there is insufficient data to characterize potential exposure from this source.

Although there is uncertainty associated with the assessment of health effects and exposure for BENPAT and BENTAX due to the limitations in the database, margins between upper-bounding estimates of exposure from environmental media and effect levels in experimental animals were adequate to address uncertainties in the health effects and exposure databases.

Conclusion

Based on the information available, it is concluded that BENPAT is entering or may be entering the environment in a quantity or concentration or under conditions that have or may have an immediate or long-term harmful effect on the environment or its biological diversity. Based on the information available, it is concluded that BENTAX is not entering the environment in a quantity or concentration or under conditions that have or may have an immediate or long-term harmful effect on the environment or its biological diversity. Additionally, components of BENPAT and BENTAX meet the criteria for persistence, but not bioaccumulation potential as set out in the Persistence and Bioaccumulation Regulations (Canada 2000).

Based on the information available, it is concluded that BENPAT and BENTAX are not entering the environment in a quantity or concentration or under conditions that have or may have an immediate or long-term harmful effect on human life and health.

Based on the available information, it is concluded that BENPAT meets one or more criteria under section 64 of CEPA 1999.

Based on the information available, it is concluded that BENTAX does not meet any of the criteria set out in section 64 of CEPA 1999.

Since BENTAX is listed on the Domestic Substances List, its import and manufacture in Canada are not subject to notification under subsection 81(1). Given the potential ecological hazards of this substance, there is concern that new activities that have not been identified or assessed could lead to this substance meeting the criteria set out in section 64 of the Act. Therefore, it is recommended to amend the Domestic Substances List, under subsection 87(3) of the Act, to indicate that subsection 81(3) of the Act applies with respect to this substance so that new manufacture, import or use BENTAX is notified and undergoes ecological and human health risk assessments.

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[US EPA] United States Environmental Protection Agency. 2010. High Production Volume Information System (HPVIS). Detailed Chemical Results for 1,4-Benzenediamine, N,N'-mixed Ph and tolyl derivs. High Production Volume Information System (HPVIS).

[WARF] Wisconsin Alumni Research Foundation. 1959. Acute Toxicity of WINGSTAY 100 to the Goodyear Tire and Rubber Company. In: US EPA 2010.

[WATERNT] Water Solubility Program [Estimation Model]. 2008. Version 1.01. Washington (DC): US Environmental Protection Agency, Office of Pollution Prevention and Toxics; Syracuse (NY): Syracuse Research Corporation. Exposure Assessment Tools and Models

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Wik A, Dave G. 2009. Occurrence and effects of tire wear particles in the environment – A critical review and an initial risk assessment. Environmental Pollution 157: 1–11.

[WSKOWWIN] Water Solubility for Organic Compounds Program for Microsoft Windows [Estimation Model]. 2008. Version 1.41. Washington (DC): US Environmental Protection Agency, Office of Pollution Prevention and Toxics; Syracuse (NY): Syracuse Research Corporation. Exposure Assessment Tools and Models

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Zeng EY, Tran K, Young D. 2004. Evaluation of potential molecular markers for urban stormwater runoff. Environmental Monitoring and Assessment 90: 23–43.

Veith AG. 1992. A review of important factors affecting tread wear. Rubber Chem Technol 65: 601-658. In: ChemRisk LLC 2009

Appendix I: Robust Study Summaries

Robust Study Summary: Evaluation of aquatic bioaccumulation potential

NoItemWeightYes/NoSpecify
1Reference: Study Submission. 2010b. Unpublished confidential studies for CAS RN 68953-84-4 submitted to Environment Canada under the Chemicals Management Plan Challenge initiative. Gatineau (QC): Environment Canada, Program Development and Engagement Division. Submission dated June 8, 2010. Bioaccumulation test in carp, Final report
2Substance identity: CAS RNn/a  
3Substance identity: chemical name(s)n/a  
4Chemical composition of the substance2Y 
5Chemical purity1Y100%
6Persistence/stability of test substance in aquatic solution reported?1Ytest substance was confirmed to be stable under storage and test conditions
7If test material is radiolabelled, were precise position(s) of the labelled atom(s) and the percentage of radioactivity associated with impurities reported?2 n/a
Method
8Reference1YJapanese Industrial Standard: Method for testing the degree of accumulation of chemical substances in fish body- method essentially the same as that in OECD Guidelines for testing of chemicals, bioaccumulation #305C
9OECD, EU, national, or other standard method?3YJapanese Industrial standard method
10Justification of the method/protocol if not a standard method was used2 n/a
11GLP (Good Laboratory Practice)3Y 
Test organism
12Organism identity: namen/a carp
13Latin or both Latin & common names reported?1YCyprinus carpio
14Life cycle age / stage of test organism1Ybased on length, weight of fish and feed type, it can be determined that they were juvenile
15Length and/or weight1Ywt = 22.9 g ave length = 9.7cm
16Sex1 n/a
17Number of organisms per replicate1Y20 fish per level 1 and 2 and 5 in control
18Organism loading rate1N 
19Food type and feeding periods during the acclimation period1Y 
Test design / conditions
20Experiment type (laboratory or field.n/a lab
21Exposure pathways (food, water, both)n/a water
22Exposure durationn/a 8 weeks
23Number of replicates (including controls)1Ytwo concentrations were tested, 20 fish per concentration, 5 fish in control
24Concentrations1 0.05mg/L and 0.005mg/L
25Food type/composition and feeding periods during the test1Y 
26If BCF/BAF derived as a ratio of chemical concentration in the organism and in water, was experiment duration equal to or longer than the time required for the chemical concentrations to reach steady state?3Ydepuration time for compound e was 5.7 days for level 1 exposure and 44.4 days for level 2 exposure
27If BCF/BAF derived as a ratio of chemical concentration in the organism and in water, were measured concentrations in both water and organism reported?3  
28Were concentrations in the test water measured periodically?1YOnce a week, Tbl 1
29Were the exposure media conditions relevant to the particular chemical reported? (e.g., for the metal toxicity - pH, DOC/TOC, water hardness, temperature)3Y 
30Photoperiod and light intensity1Y 
31Stock and test solution preparation1Y 
32Analytical monitoring intervals1Y 
33Statistical methods used1Y 
34Was solubilizer/emulsifier used, if the chemical was unstable or poorly soluble?n/aYtetrahydrofuran (20x the amount of the test substance)
Information relevant to the data quality
35Was the test organism relevant to the Canadian environment?3Y 
36Were the test conditions (pH, temperature, DO, etc.) typical for the test organism?1Y 
37Does system type and design (static, semi-static, flow-through; sealed or open; etc.) correspond to the substance's properties and organism's nature/habits?2y 
38Was pH of the test water within the range typical for the Canadian environment (6 to 9).1y7.9-8
39Was temperature of the test water within the range typical for the Canadian environment (5 to 27°C)?1Y25 +/- 2
40Was lipid content (or lipid-normalized BAF/BCF) reported?2Y3.6% ave
41Were measured concentrations of a chemical in the test water below the chemical’s water solubility?3Y 
42If radiolabelled test substance was used, was BCF determination based on the parent compound (i.e. not on total radiolabelled residues)?3 n/a
Results
43Endpoints (BAF, BCF) and valuesn/an/aBCF
44BAF or BCF determined as: 1) the ratio of chemical concentration in the organism and in water, or 2) the ratio of the chemical uptake and elimination rate constantsn/an/a(2)
45Whether BAF/BCF was derived from a 1) tissue sample or 2) whole organism?n/an/a(2)
46Whether 1) average or 2) maximum BAF/BCF was used.n/an/amaximum, i.e. ranges were presented
47Score: %97.7
48EC Reliability code:1
49Reliability category (high, satisfactory, low):High Confidence

Robust Study Summary: Evaluation of water solubility experimental data using Kollig’s approach[*]

ItemWeightResponseScore
Reference: Study Submission. 1998. Unpublished confidential studies for CAS RN 68953-83-3 submitted to Environment Canada under the New Substances Notification Regulations of CEPA 1999. Gatineau (QC): Environment Canada.
Determination of water solubility
Test substance: CAS RN: 68953-83-3
Could you repeat the experiment with available information?5Fairly well2.5
Is a clear objective stated?1Yes1
Is water quality characterized or identified (distilled or deionized)?2Yes
(reagent water obtained with a Sybron/Barnstead NANOpure II system)
2
Are the results presented in detail, clearly and understandably?3Fair
Details regarding calculations used to establish overall substance water solubility (from major and minor components) were not provided
1.5
Are the data from a primary source and not from a referenced article?3Primary3
Was the chemical tested at concentrations below its water solubility?5N/AN/A
Were particulates absent?2Not indicated
(pore size of the filter not provided)
0
Was a reference chemical of known constant tested?3Two sets of standard were analyzed by HPLC-UV with the sample set3
Were other fate processes considered?5N/AN/A
Was a control (blank) run?3N/AN/A
Was temperature kept constant?5Yes (~20 °C)5
Was the experiment done near room temperature (15-30o C)?3Yes3
Is the purity of the test chemical reported (> 98%)?3Yes (100%)3
Was the chemical's identity proven.3Yes3
Is the source of the chemical reported?1Yes1
Results:(X±SE)
Solubility (water): overall mean solubility was 1.02 mg/L
Score:82%
Degree of reliability[**]High confidence
[*] Kollig,1988.
[**] The reliability code for ecotoxicological studies from DSL categorization is used.

Appendix II: PBT Model Inputs Summary Table

Physico-Chemical Properties/Fate

EPISuite (2008) Input (all models, including: AOPWIN, KOCWIN, BCFWIN BIOWIN and ECOSAR)

StructureSMILES Code
Structure 1N(C1=CC=CC=C1)C1=CC=C(NC2=CC=CC=C2)C=C1
Structure 2CC1=C(NC2=CC=C(NC3=CC=CC=C3)C=C2)C=CC=C1
Structure 3CC1=CC=CC=C1NC1=CC=C(NC2=CC=CC=C2C)C=C1
Structure 4CC1=CC=C(NC2=CC=C(NC3=CC=CC=C3C)C=C2)C(C)=C1
Structure 5CC1=CC=C(NC2=CC=C(NC3=CC=C(C)C=C3C)C=C2)C(C)=C1

Fate

EQC (2003) (type I inputs)

ParametersBENPATBENTAXStructure 1Structure 2Structure 3Structure 4Structure 5
Molecular weight (g/mol)274.35302[1]260.31274.36288.39302.41316.44
Melting point (ºC)90-10560154130135.5168.91179.02
Data temp (ºC)2520[1]22.825252525
Vapour pressure (Pa)1x10-51x10-57.65x10-53.06x10-51.42x10-55.65x10-62.23x10-6
Log Kow3.3 – 4.64.56[1]3.33.94.64.424.56
Water solubility (mg/L)2.21.0210.130.110.0450.04890.0153
[1] physical chemical data for analogue substance BENPATAX

TaPL3 (2000)

ParametersBENPATBENTAX
Type of chemical11
Molecular weight (g/mol)288.39316.44
Melting point (ºC)10560
Data temperature (ºC)2020
Vapour pressure (Pa)1x10-51x10-5
Log Kow4.64.56
Water solubility (mg/L)2.21.02
Reaction half-life in air (h)0.60.6
Reaction half-life in water (h)43684368
Reaction half-life in soil (h)43684368
Reaction half-life in sediment (h)87608760
Reaction half-life in suspended sediment (h)43684368
Reaction half-life in fish (h)43684368
Reaction half-life in aerosol (h)1x10111x1011

Appendix III: Loss quantities for BENTAX and BENPAT and resulting estimated concentrations in environmental media

Loss quantities for BENTAX and BENPAT based on the range midpoints specified in the Mass Flow Tool output

SubstanceForm of lossReceiving compartmentVolume (kg/yr)
BENTAXWastewaterWater22.5
Air emissionAir0.5
LandfillSoil947.5
BENPATWastewaterWater600 000
LandSoil550 000
Air emissionAir5 000
LandfillSoil1 295 000

Estimated concentrations of BENTAX and BENPAT in environmental media using ChemCAN v6.00 (ChemCAN 2003)[1]

SubstanceMediumConcentration
BENTAXAir[2]0.0622 ng/m3
Water[3]3.05 ng/L
Soil[3]55.2 ng/g solids
Sediment[3]104 ng/g solids
BENPATAir[2]0.0635 ng/m3
Water[3]5 361 ng/L
Soil[3]14 694 ng/g solids
Sediment[3]16 838 ng/g solids
[1] All modelling assumed release into the region of southern Ontario (Ontario Mixed-Wood Plain).
[2] Atmospheric oxidation half-lives were estimated using AOPWIN v1.92 (AOPWIN 2008).
[3] Due to persistence in water, soil and sediment, negligible degradation was assumed in these environmental compartments.

Appendix IV: Upper-bounding estimates of daily intakes of BENPAT for various age groups (µg/kg-bw per day)

Route of exposure0–0.5 years[1], [2], [3]0.5–4 years[4]5–11 years[5]12–19 years[6]20–59 years[7]60+ years[8]
Breast milk fedFormula fedNot formula fed
Air[9]1.78 × 10-51.78 × 10-51.78 × 10-53.81 × 10-52.97 × 10-51.69 × 10-51.45 × 10-51.26 × 10-5
Drinking water[10]N/A5.72× 10-12.14 × 10-12.42× 10-11.90 × 10-11.08 × 10-11.13 × 10-11.19 × 10-1
Food and beverages[11]N/AN/AN/AN/AN/AN/AN/AN/A
Soil[12]5.88 × 10-25.88 × 10-25.88 × 10-29.48 × 10-23.08 × 10-27.42 × 10-36.22 × 10-36.12 × 10-3
Total intake5.88 × 10-26.31 × 10-12.73 × 10-13.37 × 10-12.21 × 10-11.16× 10-11.20 × 10-11.25 × 10-1
N/A, not available
[1] No quantitative data were identified for concentrations of BENPAT in breast milk.
[2] Assumed to weigh 7.5 kg, to breathe 2.1 m3 of air per day, to drink 0.8 L of water per day (formula fed) or 0.3 L/day (not formula fed) and to ingest 30 mg of soil per day (Health Canada 1998).
[3] For exclusively formula-fed infants, intake from water is synonymous with intake from food. No quantitative data on concentrations of BENPAT in drinking water or formula were identified for Canada. The concentration of BENPAT in drinking water was estimated using ChemCAN v6.00 at 5 361 ng/L (ChemCAN 2003). For non-formula-fed infants, approximately 50% are introduced to solid foods by 4 months of age and 90% by 6 months of age (NHW 1990).
[4] Assumed to weigh 15.5 kg, to breathe 9.3 m3 of air per day, to drink 0.7 L of water per day and to ingest 100 mg of soil per day (Health Canada 1998).
[5] Assumed to weigh 31.0 kg, to breathe 14.5 m3 of air per day, to drink 1.1 L of water per day and to ingest 65 mg of soil per day (Health Canada 1998).
[6] Assumed to weigh 59.4 kg, to breathe 15.8 m3 of air per day, to drink 1.2 L of water per day and to ingest 30 mg of soil per day (Health Canada 1998).
[7] Assumed to weigh 70.9 kg, to breathe 16.2 m3 of air per day, to drink 1.5 L of water per day and to ingest 30 mg of soil per day (Health Canada 1998).
[8] Assumed to weigh 72.0 kg, to breathe 14.3 m3 of air per day, to drink 1.6 L of water per day and to ingest 30 mg of soil per day (Health Canada 1998).
[9] No quantitative data were identified for concentrations of BENPAT in air. The concentration of BENPAT in air was estimated using ChemCAN v6.00 at 0.0635 ng/m3 (ChemCAN 2003).
[10] No quantitative data were identified for concentrations of BENPAT in drinking water. The concentration of BENPAT in drinking water was estimated using ChemCAN v6.00 at 5 361 ng/L (ChemCAN 2003).
[11] No quantitative data were identified for concentrations of BENPAT in food or beverages.
[12] No quantitative data were identified for concentrations of BENPAT soil. The concentration of BENPAT in soil was estimated using ChemCAN v6.00 at 14 694 ng/g solids (ChemCAN 2003).

Appendix V: Summary of health effects information for BENPAT, BENTAX and analogue BENPATAX

EndpointsLowest effect levels[1] / Results
Acute toxicity

BENPAT (CAS RN 68953-84-4)

Lowest oral LD50(rat) > 2000 mg/kg-bw (Bayer AG 1990; ECB 2003)

Other oral LD50(rat) > 4000- 5000 mg/kg-bw (Pharmakon 1993b; WARF 1959)

Dermal LD50 (rabbit) > 2000 mg/kg-bw (Springborn Laboratories 1995a; ECB 2003)

BENTAX (CAS RN 68478-45-5)

Lowest oral LD50(rat) > 6130 mg/kg-bw (Goodyear Tire and Rubber Company 1992b)

BENPATAX (analogue, CAS RN 68953-83-3)

Oral LD50(rat) = between 2000 mg/kg-bw and 5000 mg/kg-bw (Merriman 1995a)

Dermal LD50 (rabbit) > 2000 mg/kg-bw (Merriman 1995b)

No inhalation studies were identified.

Short-term repeated-dose toxicity

BENPAT (CAS RN 68953-84-4)

Lowest oral LOEL = 7.5 mg/kg-bw per day based on increased urothelial cell proliferation in bladder in both sexes of Fischer 344 rats (14 rats/sex/group) exposed by diet to 0, 7.5, 30 or 120 mg/kg-bw BENPAT for 4 weeks. Increased liver and kidney weights in mid-dose females and in high-dose males and females; increased heart and spleen weight and decreased body weight in high dose females (with reduced food consumption) were observed. Increase cell division for liver and decrease cell division for kidney cells were also observed (mid-dose males and high-dose males and females). Reversible hematological signs (including increased mean corpuscular volume, and decreased mean corpuscular hemoglobin level) and clinical chemistry changes (including increased blood bilirubin and cholesterol levels) occurred in high-dose groups. The authors of the study considered 30 mg/kg-bw to be the LOAEL for this study based on increased urothelial cell proliferation in bladder in both sexes of animals and increased liver and kidney weight in mid-dose females (AHF 1996a).

Other oral LOEL = 100 mg/kg-bw per day based on significantly dose related decrease in body weight, increase in liver weight and hepatocellular labelling index (0.1g/kg) in both sexes of Fischer 344/N TacfBR rats exposed by gavage to 0, 100, 300, 1000 or 3000 mg/kg-bw per day of BENPAT for 21 days. Doses of 1000 and 3000 mg/kg-bw were lethal to male and female rats after 6 days exposure (AHF 1994).

BENPATAX (analogue, CAS RN 68953-83-3)

Lowest oral LOEL = 120 mg/kg-bw per day based on macrocytic anemia [higher mean corpuscular volume (MCV) and lower mean corpuscular hemoglobin concentration (MCHC)] , compensatory extramedullary erythropoiesis, bodyweight gain reduction, increases in relative liver, kidney and brain weights. increases in total bilirubin, cholesterol, albumin and total protein values in high dose male and female Fischer 344 rats (6 to 8 rats/sex/group) exposed by diet to 0, 7.5, 30 or 120 mg/kg-bw of Wingstay 200 (trade name for BENPATAX) for 28 days. Hyperplasia of the urothelium and increased urothelial cell proliferation were also seen in high dose groups (Iatropoulos et al. 1998).

No short-term studies were identified forBENTAX and no dermal or inhalation studies were identified for all three compounds.

Subchronic toxicity

BENPAT (CAS RN 68953-84-4)

Oral LOAEL: Groups of male Fischer 344 rats (number not specified) were exposed by diet to 1900 ppm (equivalent to 95 mg/kg-bw per day; based on Health Canada 1994) of BENPAT for 38 weeks (accelerated bioassay designed to assess tumour induction and promotion potential in target organs (liver and urinary bladder)). The substance exerted chronic anemia, accompanied by body weight reduction, compensary extramedullary erythropoiesis in liver and spleen, increases in kidney and heart weights and increases in total bilirubin and decreases in total protein, albumin and biliprotein (bilirubin plus albumin). There was an absence of tumour initiating or promoting activity. (AHF 1996b; Iatropoulos et al. 1997).

No subchronic studies were identified for BENTAX and BENPATAX and no dermal or inhalation studies were identified for all three compounds.

Chronic toxicity/ carcinogenicity

BENPAT (CAS RN 68953-84-4)

Oral LOAEL (non-neoplastic) = 2.7 mg/kg bw per day based on a significant increase in urothelial cell proliferation and hyperplasia observed at all doses tested in both sexes of Fischer 344 rats exposed via the diet to 0, 53, 310 and 1900 ppm (equivalent to 0, 2.7, 15.5 and 95 mg/kg-bw per day; based on Health Canada 1994) of BENPAT for 52 weeks (followed by a 12-week recovery period). Increases in relative liver, spleen, heart and kidney weights; and decreases in body weight gain and food consumption were reported in high dose groups. Significantly increased mean corpuscular volume (MCV) and decreased mean corpuscular hemoglobin concentration (MCHC) and red blood cell count were also observed in high dose groups, accompanied by microscopic evidence of extramedullary erythropoiesis in the spleen and liver. Increased blood bilirubin, cholesterol level and decreased total protein level were noticed in high dose treated animals. No evidence of treatment related carcinogenic activity was found (AHF 1996c; Iatropoulos et al. 1997).

BENPATAX (analogue, CAS RN 68953-83-3)

Oral LOAEL (non-neoplastic) = 20 mg/kg bw based on macrocytic anemia in a 52-week repeated dose study in Fischer 344 rats (20 rats/sex/group) exposed via the diet to 0, 4, 20 and 100 mg/kg-bw per day of BENPATAX for 52-week with a 12-week recovery period. Observed effects included increased in methemoglobin in both sexes of rats, increased in platelet and reticulocyte count and decreases in red blood cell counts, hemoglobin and hematocrit in male rats. Additional effects, such as increased MCV, decreased MCHC and decreased serum folate, folic acid and iron levels were also observed in rats treated at the high dose. Reduced body weight, increased relative liver, kidney and thyroid weight, extensive congestion of the spleen and increased cell proliferation in the urinary bladder as further evidences of macrocytic anemia were also reported mainly in rats treated at the high dose (Iatropoulos et al. 2000).

No long-term studies were identified for BENTAX and no dermal or inhalation studies were identified forall three compounds.

Reproductive & Developmental Toxicity

BENPAT (CAS RN 68953-84-4)

Groups of 30 male and female Sprague-Dawley rats were exposed via the diet to 0, 120, 400 and 1500 ppm (equivalent to 0, 6, 20 and 75 mg/kg-bw per day, using a dose conversion by Health Canada 1994) of BENPAT during 10 weeks premating, 2 weeks mating, 3 weeks gestation and through to the weaning period of pups (21 days) in a two-generation study.

Oral LOAEL for reproductive and developmental toxicity = 6 mg/kg-bw per day based on prolonged gestational length for F1 dams and polycystic lesions in kidneys of F1 and F2 weanlings. Kidney lesions were considered to be dose related. Prolonged gestational length and increased pup body weights were also observed at 20 and 75 mg/kg-bw per day for F0 dams with F1 litters. Dystocia and delayed parturition were observed in F0 and F1 dams and post implantation loss/litter was significantly increased at 20 and 75 mg/kg-bw per day for F1 litters and at 75 mg/kg-bw per day for F2 litters, the numbers of total pups and live pups per litter were significantly reduced at 20 and 75 mg/kg-bw for F1 and at 75 mg/kg-bw for F2 litters. A significant increase in the numbers of dead pups and reduced live birth index at 75 mg/kg-bw were reported for F0 and F1 dams. No evidence of male reproductive toxicity noticed in F0 or F1.

Oral LOAEL for systemic toxicity = 6 mg/kg-bw per day based on polycystic lesions in kidney observed at all dose levels in F0 females and F1 parents. Mortality during gestation/lactation was seen in mid (3/24; 1/22) and high dose (4/25; 1/24) groups for F0 and F1. Body weights decreases were observed in high dose females (Goodyear Tire and Rubber Company 2001).

Other study: a mechanistic study confirmed results in above 2-generation reproductive toxicity study in rats; it demonstrated that oral exposure of BENPAT at 2500 ppm (equivalent to 125 mg/kg-bw per day, using a dose conversion by Health Canada 1994) induced dystocia, delayed parturitition and an associated decrease in pup survival at birth. Study indicated that only gestational exposure was necessary and sufficient to cause dystocia. It is necessary and sufficient to expose F0 dams during gestation and/or lactation to produce polycystic kidneys in F1 offspring. However, it is uncertain whether gestational exposure alone would induce the polycystic kidneys. Pre-gestational exposure did not enhance the effects attributed to gestational BENPAT ingestion (Goodyear Tire and Rubber Company 2001).

Other study: inseminated female Sprague-Dawley rats (25/group) exposed by gavage to 0, 20, 70 and 200 mg/kg-bw per day of BENPAT for 10 days (gestational day 6-15).

Oral LOEL for developmental toxicity = 200 mg/kg-bw based on decreased foetal body weights. Pregnancy rates, litter sizes, number of live foetuses, uterine implantation, and all gestational parameters were unaffected by chemical treatment.

Oral LOEL for systemic toxicity = 200 mg/kg-bw based on reduced maternal body weights and food consumption at the highest dose only. NOEL for this study is 70 mg/kg-bw.

Oral NOEL (teratogenic) = ≥ 200 mg/kg-bw per day based on no treatment-related abnormalities (malformations or variations) in the study (ECB 2003).

BENPATAX (analogue, CAS RN 68953-83-3)

Sprague-Dawley CD rats (25/group) were exposed by gavage to 0, 20, 70 and 200 mg/kg-bw per day for 10 (1 high dose group only) or 14 days (3 groups) during gestation.

Oral LOEL for developmental toxicity = 70 mg/kg-bw per day based on reduced foetal bodyweights observed in mid- and high-dose groups in F1 rats.

Oral LOEL for systemic toxicity = 70 mg/kg-bw based on decreases in bodyweights, bodyweight gains and food consumption in F0 females.

NOEL of 20 mg/kg-bw for maternal and developmental toxicity and NOEL of ≥ 200 mg/kg-bw for teratogenic toxicity were established for this study (Tyl 1996).

No reproductive/developmental studies were identified forBENTAX (CAS RN 68478-45-5)

Genotoxicity and related endpoints: in vivo

Micronucleus assay

BENPAT (CAS RN 68953-84-4)

Negative: Bone marrow of CD-1 mice; single i.p. injection at 0, 250, 1250 and 2500 mg/kg-bw (Pharmakon 1993a)

DNA Adduct Analysis (P32 post-labelling)

BENPAT (CAS RN 68953-84-4)

Negative: Liver and urinary bladder cells of Fischer 344/N TacfBR rats orally exposed by gavage at doses of 0, 300, 1000 and 3000 mg/kg bw per day for 7 days (AHF 1995)

Gene mutation (Drosophila Sex-Linked Recessive Lethal Test )

BENPAT (CAS RN 68953-84-4)

Negative: Drosophila melanogaster were fed of 0.01, 0.05 mg/ml for 24hours (ECB 2003; Goodyear Tire and Rubber Company 1992a)

Negative: Drosophila melanogaster were fed of 0.05 and 0.63 mg/ml for 24hours (ECB 2003; Litton Bionetics 1979; Goodyear Tire and Rubber Company 1992a)

BENTAX (CAS RN 68478-45-5)

Negative: Drosophila melanogaster wild type and Muller-s (bar-eye mutation on the X-chromosome) at oral doses of 0.01, 0.001 and 0.0001 mg/ml for 16hours (Goodyear Tire and Rubber Company 1992c)

Genotoxicity and related endpoints: in vitro

Gene mutation

BENPAT (CAS RN 68953-84-4)

Positive: Salmonella typhimurium, strains TA98, TA 1537 and TA1538 with metabolic activation

Negative: Salmonella typhimurium, strains TA98 and TA1538 and Escherichia coli WP2 without metabolic activation; S. typhimurium, strains TA100, TA1535, TA1537 and Escherichia coli strain WP2 uvrA with and without metabolic activation (ECB 2003 and Goodyear Tire and Rubber Company 1992a)

BENTAX (CAS RN# 68478-45-5)

Positive: Salmonella typhimurium, strains TA98, TA 1537 and TA1538 with metabolic activatio.

Negative: Salmonella typhimurium, strains TA100 and TA1535 with and without metabolic activatio.

(Goodyear Tire and Rubber Company, 1992c)

Positive: Salmonella typhimurium, strains TA98, TA 100, TA1535 and TA1537 with metabolic activatio.

(Goodyear Tire and Rubber Company 1992d)

BENPATAX (analogue, CAS RN 68953-83-3)

Positive: Salmonella typhimurium, strains TA98, TA 1537 and TA1538 with metabolic activatio.

Negative: Salmonella typhimurium, strains TA100 and TA1535 and E. coli WP2uvrA with and without metabolic activation (Stankowski 1998)

Chromosomal aberration (Cytogenetic assay)

BENPAT (CAS RN 68953-84-4)

Negative: Chinese hamster ovary (CHO) cells with or without metabolic activation (ECB 2000, 2003).

BENPATAX (analogue, CAS RN 68953-83-3)

Negative: CHO cells with or without metabolic activation (SanSebastian 1994).

DNA damage and repair assay

BENPAT (CAS RN 68953-84-4)

Positive: Escherichia coli Pol A1 & Escherichia coli Pol A1- strains W 3110 (Pol A+) and p 3478 (Pol A-) without metabolic activation (ECB 2003; Goodyear Tire and Rubber Company 1992a)

BENTAX (CAS RN 68478-45-5)

Positive: Escherichia coli (Pol A1- ) without metabolic activation (Goodyear Tire and Rubber Company 1992c&d)

In Vitro Transformation assay

BENPAT (CAS RN 68953-84-4)

Negative : Balb/3T3 mouse cells without metabolic activation (ECB 2003; Goodyear Tire and Rubber Company 1992a)

Unsheduled DNA Synthesis Assays (UDS)

BENPAT (CAS RN 68953-84-4)

Negative: Rat hepatocytes without metabolic activation (Hepatocytes capable of metabolic activation) (AHF 1999).

BENPATAX (analogue, CAS RN 68953-83-3)

Negative: Rat hepatocytes without metabolic activation (Jeffrey 1999).

Irritation & Sensitization

Skin irritation

BENPAT (CAS RN 68953-84-4)

No skin irritation was observed in rabbit exposed to BENPAT for 4 hours (Bayer AG 1991) and in albino rabbits exposed to a 20% suspension of BENPAT (WARF 1959).

In a Draize test, slight irritation (slight redness) was reported at test sites in albino rabbits treated with 500 mg of BENPAT for a period up to 72 hours (WARF 1959).

BENPATAX (analogue, CAS RN 68953-83-3)

Slight irritation to the skin was observed in New Zealand white rabbits treated with BENPATAX for 4 hours (observation period went up to 10 days). Additional observation included desquamation and test site stained brown (Merriman 1995c).

In a Draize test, slight to moderate skin irritation was reported in New Zealand white rabbits (5/sex) after treatment with BENPATAX at 2000 mg/kg on 10% of body surface for 24 hours (observation period went up to 14 days) (Merriman 1995b).

No skin irritation studies were identified for BENTAX (CAS RN 68478-45-5).

Eye irritation

BENPAT (CAS RN 68953-84-4)

No eye irritation was reported in rabbit after 24 hours (no detail provided, Bayer 1991).

Mild and reversible eye irritation was observed in rabbits (Draize test) exposed to 0.06g (0.1 ml) of BENPAT up to 72 hours. The test substance is considered to be a “mild irritant’’ to the eye (Springborn Laboratories 1995b).

No eye irritation studies were identified for BENTAX (CAS RN 68478-45-5) & BENPATAX (analogue, CAS RN 68953-83-3)

Sensitization

BENPAT (CAS RN 68953-84-4)

In a maximization test, albino guinea pigs were challenged and rechallenged (7 days later) with 25% and 100% of BENPAT following intracutaneous induction at 5 and 100% of BENPAT. Weak skin responses (erythema and oedema) were observed. The test substance is considered to be a contact sensitizer (Springborn Laboratories 1995c).

BENPATAX (analogue, CAS RN 68953-83-3)

In a guinea pig maximization test, weak skin responses (erythema and oedema) were observed when test animals were challenged with 40% BENPATAX following intradermal induction at 5 and 100% active substance. BENPATAX was sensitising to the skin of guinea pigs (Merriman 1995d).

No sensitization studies were identified for BENTAX (CAS RN# 68478-45-5)

Human studies
Genotoxicity-
In vitro
(Diaryl-p-phenylendiamines mixed)
Urinary mutagenicity study of occupational exposures in the rubber industry of 72 workmen (44 smokers) employed in a tyre plant showed that smoking habits, but not occupation, were statistically significantly related to the appearance of a positive urinary mutagenic activity in Salmonella typhimurium, strains TA98. A possible synergistic effect of occupation with smoking was observed among tyre builders who were also smokers. The study of the raw materials showed that mixed diaryl-p-phenylendiamines was weakly active as mutagens in strain TA98 in the presence of metabolic activation (Crebelli et al. 1985).
[1]LC50, median lethal concentration; LD50, median lethal dose; LOAEL, lowest-observed-adverse-effect level; LOEL, lowest-observed-effect level; NOEL, no-observed-effect level.

Appendix VI: Summary of margins of exposure for BENPAT

Exposure scenarioConcentration or intakeCritical effect levelCritical effectMargin of exposure
Estimated daily intake from environmental media[1]0.06 –0.63 µg/kg-bw per day (BENPAT)2.7 mg/kg-bw per da.Long-term repeated dose oral exposure level (LOAEL) for increase urothelial cell proliferation and hyperplasia observed in all dose tested in both sexes of rats in a 52-week study with BENPAT (CAS RN 68953-84-4) (AHF 1996b; Iatropoulos et al. 1997).4 285– 45 000
6.0 mg/kg-bw per da.Repeated dose oral exposure level (LOAEL) for treatment related polycystic lesions in kidneys observed at all dose levels in F1 parents and F1 and F2 weanlings, and prolonged gestation length in F1 dams, in a 2-generation rat study with BENPAT (CAS RN 68953-84-4) (Goodyear Tire and Rubber Company 2001).9 520 – 100 000
20 mg/kg-bw per da.Long-term repeated dose oral exposure level (LOAEL) for treatment related macrocytic anemia in a 52-week study with BENPATAX (CAS RN 68953-84-4) (Iatropoulos et al. 2000).31 745 – 333 300
[1]Estimated daily intake based on maximum intake from all substance. See Appendix IV.

Footnotes

[1] The Chemical Abstracts Service Registry Number (CAS RN) is the property of the American Chemical Society and any use or redistribution, except as required in supporting regulatory requirements and/or for reports to the government when the information and the reports are required by law or administrative policy, is not permitted without the prior, written permission of the American Chemical Society.
[2] A determination of whether one or more of the criteria of section 64 are met is based upon an assessment of potential risks to the environment and/or to human health associated with exposures in the general environment. For humans, this includes, but is not limited to, exposures from ambient and indoor air, drinking water, foodstuffs, and the use of consumer products. A conclusion under CEPA 1999 on the substances in the Chemicals Management Plan (CMP) Challenge Batches 1-12 is not relevant to, nor does it preclude, an assessment against the hazard criteria specified in the Controlled Products Regulations, which is part of regulatory framework for the Workplace Hazardous Materials Information System [WHMIS] for products intended for workplace use. Similarily, a conclusion based on the criteria contained in section 64 of CEPA 1999 does not preclude actions being taken under other sections of CEPA or other Acts.
[3] Given the log Kow values of the representative Structures 1 – 3 of BENPAT and representative
Structures 3 – 5 of BENTAX, elimination via metabolism may be less important than gill elimination as the mass-balance model suggests. However, because this is uncertain, a kM of 0.094 days-1 was used for further model predictions.
[4] Calculation is based on the following information:
- 48-hour EC50 = 1.5 g of rubber/L for D.magna when organisms were exposed to water leachate obtained from immersing rubber samples containing 1.9% of BENPAT in water for 72 hours (Wik 2007)
- 48-hour EC50 = 1.8 mg/L for D.magna from exposure to BENPAT (see Table 7, Study Submission 2010b, IUCLID Data Set 2003)
- Therefore, it is assumed that the concentration of BENPAT in water in the Wik (2007) study is 1.8 mg/L. Hence, 1.5 g/L x 1.9% = 0.0285g/L of BENPAT, and 1.8 mg/L / 28.5 mg/L = 6.3%
- This calculation assumes that the toxicity to D.magnaobserved in Wik (2007) is attributable to BENPAT.