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Screening Assessment for The Challenge
1-Propanol, 2-methoxy
(2-Methoxypropanol)

Chemical Abstracts Service Registry Number
1589-47-5


Environment Canada
Health Canada

February 2009

Synopsis

The Ministers of the Environment and of Health have conducted a screening assessment of 1-propanol, 2-methoxy- (2-methoxypropanol), Chemical Abstracts Service Registry Number 1589-47-5. The substance 2-methoxypropanol was identified in the categorization of the Domestic Substances List as a high priority for action under the Ministerial Challenge. 2‑Methoxypropanol was identified as a high priority because it was considered to pose an intermediate potential for exposure of individuals in Canada and had been classified by the European Commission on the basis of developmental toxicity. The substance did not meet the ecological categorization criteria for persistence, bioaccumulation potential or inherent toxicity to aquatic organisms. Therefore, the focus of this assessment of 2‑methoxypropanol relates principally to human health risks.

2-Methoxypropanol is a by-product in the manufacture of commercial propylene glycol monomethyl ether. According to data submitted under section 71 of Canadian Environmental Protection Act, 1999 (CEPA 1999), 2-methoxypropanol was not manufactured in Canada in 2006 above the reporting threshold of 100 kg. The total quantity imported into Canada in the same calendar year was reported to be in the range of 100 000–1 000 000 kg. 2-Methoxypropanol is used mainly in industrial solvents and paints. Less than 100 kg of 2-methoxypropanol was reported to be released into the environment.

Population exposure to 2-methoxypropanol in Canada is expected to be predominantly by the dermal and inhalation routes during use of consumer products containing the substance as an impurity. Based on very limited information on releases and concentrations in environmental media as well as the results of fugacity modelling, exposure to 2‑methoxypropanol from the general environment is expected to be negligible. The critical health effect associated with exposure to 2-methoxypropanol is primarily developmental toxicity, based on observations in experimental animals. Although the margin between measured concentrations in indoor air and concentrations associated with effects in experimental animals is large, margins between conservative upper-bounding estimates of concentrations in indoor air during use of consumer products containing 2-methoxypropanol as an impurity and critical effect levels for developmental effects in experimental animals may not be adequately protective. In addition, use of some consumer products may result in exposure to 2-methoxypropanol through skin contact. However, available data are inadequate to characterize risk to health associated with dermal exposure to 2-methoxypropanol in products.

On the basis of the potential inadequacy of the margin between estimated exposure via inhalation during use of some consumer products and critical effect levels for developmental toxicity, it is concluded that 2-methoxypropanol be considered a substance that may enter the environment in a quantity or concentration or under conditions that constitute or may constitute a danger in Canada to human life or health.

On the basis of low ecological hazard, low expected releases and expected low environmental exposure of 2-methoxypropanol, it is concluded that this substance 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 or that constitute or may constitute a danger to the environment on which life depends. 2-Methoxypropanol does not meet the criteria for persistence or bioaccumulation as set out in the Persistence and Bioaccumulation Regulations.

This substance will be included in the upcoming Domestic Substances List inventory update initiative. In addition and where relevant, research and monitoring will support verification of assumptions used during the screening assessment and, where appropriate, the performance of potential control measures identified during the risk management phase.

Based on the information available, it is concluded that 2-methoxypropanol meets one or more of the criteria set out in section 64 of CEPA 1999.

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 results of a screening assessment, the Ministers can propose to take no further action with respect to the substance, to add the substance to the Priority Substances List for further assessment or to recommend that the substance be added to the List of Toxic Substances in Schedule 1 of the Act and, where applicable, the implementation of virtual elimination.

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; 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 the Canada Gazette, Part I, on December 9, 2006 (Canada 2006), which 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 substance 1-propanol, 2-methoxy- (2-methoxypropanol) was identified as a high priority for assessment of human health risk because it was considered to present IPE and had been classified by another agency on the basis of developmental toxicity.

The Challenge for 2-methoxypropanol was published in the Canada Gazette on August 18, 2007 (Canada 2007). A substance profile was released at the same time. The substance profile presented the technical information available prior to December 2005 that formed the basis for categorization of this substance. As a result of the Challenge, submissions of information were received.

Although 2-methoxypropanol was determined to be a high priority for assessment with respect to human health, it did not meet the criteria for potential for persistence, bioaccumulation or inherent toxicity to aquatic organisms. Therefore, this assessment focuses principally on information relevant to the evaluation of risks to human health.

Under CEPA 1999, screening assessments focus on information critical to determining whether a substance meets the criteria for defining a chemical as toxic as set out in section 64 of the Act, where

“64. […] a substance is toxic if it is entering or may enter the environment in a quantity or concentration or under conditions that

  1. have or may have an immediate or long-term harmful effect on the environment or its biological diversity;
  2. constitute or may constitute a danger to the environment on which life depends; or
  3. constitute or may constitute a danger in Canada to human life or health.”

Screening assessments examine scientific information and develop conclusions by incorporating a weight of evidence approach and precaution as required under CEPA 1999.

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 this substance were identified in original literature, review and assessment documents and stakeholder research reports and from recent literature searches, up to June 2008 for the exposure section of the document and up to June 2007 for the health effects section. Key studies were critically evaluated; modelling results may have been used to reach conclusions. Evaluation of risk to human health involves consideration of data relevant to estimation of exposure (non-occupational) of the general population, as well as information on health hazards (based principally on the weight of evidence assessments of other agencies that were used for prioritization of the substance). Decisions for human health are based on the nature of the critical effect and/or margins between conservative effect levels and estimates of exposure, taking into account confidence in the completeness of the identified databases on both exposure and effects, within a screening context. The screening assessment does not represent an exhaustive or critical review of all available data. Rather, it presents a summary of the critical information upon which the conclusion is based.

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. This assessment has undergone external written peer review/consultation. Comments on the technical portions relevant to human health were received from scientific experts selected and directed by Toxicology Excellence for Risk Assessment (TERA), including Donna J. Vorhees (The Science Collaborative – North Shore), Harlee Strauss (H. Strauss Associates, Inc.) and Joan Strawson (TERA). Comments on these sections were also received from ToxEcology Environmental Consulting Ltd. Additionally, the draft of this screening assessment was subject to a 60-day public comment period. Although external comments were taken into consideration, the final content and outcome of the screening risk assessment remain the responsibility of Health Canada and Environment Canada.

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

Substance Identity

For the purposes of this document, the substance 1-propanol, 2-methoxy- will be referred to as 2-methoxypropanol.

Commercial propylene glycol monomethyl ether (PGME) is a mixture of two isomers. It consists mainly of 1-methoxy-2-propanol (alpha isomer of PGME, CAS RN 107-98-2), with lesser amounts of 2-methoxypropanol (beta isomer of PGME), which is considered an impurity (OECD 2001; EURAR 2006). 2-Methoxypropanol is a by-product of the reaction to form 1-methoxy-2-propanol, which involves combining ethylene oxide with an alcohol (De Kettenis 2005). This substance is a colourless, combustible liquid that is completely miscible in water.

Table 1. Substance identity of 2-methoxypropanol

CAS RN

1589-47-5

DSL 1name

1-Propanol, 2-methoxy-

NCI names2

1-Propanol, 2-methoxy- (TSCA)
2-Methoxypropanol (EINECS)

Other names

2-Methoxy-1-hydroxypropane; 2-Methoxy-1-propanol; beta-Propylene glycol monomethyl ether (beta-PGME)

Chemical group

Organics

Chemical subgroup

Alcohols

Chemical formula

C4H10O2

Chemical structure

Image of chemical structure of CAS RN 1589-47-5

SMILES

OCC(OC)C

Molecular mass

90.12 g/mol
1 DSL (Domestic Substances List).
2 EINECS (European Inventory of Existing Chemical Substances); TSCA (Toxic Substances Control Act Chemical Substances Inventory).
Abbreviations: CAS RN, Chemical Abstracts Service Registry Number; DSL, Domestic Substances List; EINECS, European Inventory of Existing Commercial Chemical Substances; NCI, National Chemical Inventories; SMILES, simplified molecular input line entry specification; TSCA, Toxic Substances Control Act Chemical Substance Inventory.
Source: NCI (2007)

Physical and Chemical Properties

Table 2 contains the experimental and modelled physical and chemical properties of 2‑methoxypropanol that are relevant to its environmental fate.

Table 2. Physical and chemical properties for 2-methoxypropanol

Property Type Value Temperature
(°C)
Reference

Melting point (°C)

Modelled

-55.74  

MPBPWIN 2000

Boiling point (°C)

Experimental

130  

PhysProp 2006

Density (g/cm3)

 

0.938 20

Lide 2006

Vapour pressure (Pa)

Modelled

544
(4.08 mm Hg)
25

MPBPWIN 2000

592 25

ACD 2007

Henry’s Law constant
(Pa·m3/mol)

Modelled

1.84 × 10-3 to
5.63 × 10-3
(1.813 × 10-8 to
5.56 × 10-8
atm·m3/mol)1
25

EPIWIN 2004

Log Kow
(dimensionless)

Modelled

-0.49 25

KOWWIN 2000

-0.45 25

ACD 2007

Log Koc
(dimensionless)

Modelled

0.00  

PCKOCWIN 2000

1.13 25

ACD 2007

Water solubility (mg/L)

Modelled

1 000 000 25

WSKOWWIN 2000

166 000 25

ACD 2007

pKa

Modelled

14.44 25

ACD 2007

Abbreviations: Koc, organic carbon partition coefficient; Kow, octanol–water partition coefficient.
1 The value in parentheses is the value originally reported in the reference.

Sources

No natural sources of 2-methoxypropanol have been identified.

2-Methoxypropanol is not produced commercially (OECD 2003). It is an impurity generated in the process of PGME manufacture. The production of PGME involves a catalytic reaction of methanol and propylene oxide under elevated pressure and temperature. The resulting product is separated via distillation. Excess methanol is recovered in the first distillation column and recycled back into the reaction. 1-Methoxy-2-propanol is recovered in the second distillation column, whereas 2-methoxypropanol is collected in the third distillation column (EURAR 2006). PGME products are considered to consist of no more than 5% 2-methoxypropanol (Hellwig et al. 1994; Verschueren 2001; CHEMINFO 2007). According to the European Marketing and Use Directive 76/769/EEC, 2-methoxypropanol should not be in consumer goods at concentrations above 0.5% ( De Kettenis 2005; European Commission 2007).

Based on the information submitted under section 71 of CEPA 1999, no Canadian companies reported manufacturing 2-methoxypropanol above the reporting threshold of 100 kg in 2006. The total quantity imported into Canada in the same calendar year was reported to be in the range of 100 000–1 000 000 kg (Environment Canada c2008).

Uses

According to submissions made under section 71 of CEPA 1999, 2-methoxypropanol is found as an impurity in PGME, which is a solvent used in paints, stains and coatings, as well as in inks used for packaging (Environment Canada c2008). Although 2-methoxypropanol is only an impurity, found at concentrations less than 5%, PGME is a high production volume chemical (OECD 2001) and was categorized as having GPE in Canada. 2-Methoxypropanol may be present in pest control products as an impurity of the formulant PGME (2008 e-mail from Pest Management Regulatory Agency, Health Canada, to Existing Substances Bureau, Health Canada; unreferenced). 2-Methoxypropanol may be present as an impurity in nail enamel, nail polish remover, hair conditioner, hair dye, hair spray and false eyelash adhesive, as well as in a solvent to remove false eyelashes, as these products were identified as containing PGME (2008 report from Cosmetics Division, Product Safety Programme, Health Canada, to Existing Substances Bureau, Health Canada; unreferenced; CNS 2008).

2-Methoxypropanol may be present as an impurity in solvents used in the manufacture of inks, lined varnishes and coatings (interior and exterior) in paperboard and plastic food packaging applications; however, the solvents are not expected to be present in the finished food packaging materials. PGME is used in the compositions of cleaners that require rinsing of treated surfaces with potable water in food plants. PGME is also an intermediate substance in the production of propylene glycol monomethyl ether acetate (PMA) and may contain 2-methoxypropanol as an impurity. PMA is used as a solvent in the manufacture of epoxy resins that are used as coatings on the interior of railway hopper cars, farm storage bins and truck trailers to store or transport dry food products. PGME and PMA are also used as solvents in the formulations of products applied on non-food contact surfaces, which must be used under well-ventilated conditions where there will be no accumulation of solvent vapours in food processing areas. Human exposures to 2-methoxypropanol from these food packaging–related uses are considered to be negligible (2008 and 2009 e-mails from Food Packaging Materials and Incidental Additives Section, Food Directorate, Health Canada, to Existing Substances Bureau, Health Canada; unreferenced).

Although 2-methoxypropanol is not produced commercially, given that exposure to this substance may occur as a result of exposure to PGME, a list of the potential and historical uses of the latter substance is also included in this section; however, it is uncertain whether these uses occur in Canada.

PGME is mainly used as a chemical intermediate in the manufacture of PMA, but it may also be used as a solvent in surface coatings, varnishes, paints and agricultural pesticides (OECD 2001; Dow 2004). This substance may also be used as a solvent or coupling agent in various types of inks, cleaners—including automotive cleaners, window and oven cleaners, carpet and upholstery cleaners (OECD 2001; 3M 2002; Noveon 2006a, b, c) and hard-surface cleaners (Dow 2004)—and rust removers (Dow 2004).

2-Methoxypropanol may be found at a low concentration (<5%) in other PGME-containing products, including adhesives, electronics, non-structural caulking compounds and sealants, synthetic resins and rubber adhesives (OECD 2001; Imperial 2004), plaster (HPD 2007), paint stripper, concrete floor primer, polyurethane varnish, wallpaper remover, spot remover, and kitchen and bath wipes (HPD 2008). It may also be found in products used for surface treatments, wood protection, waterproofing, shoes and leather, metals and the galvano technique, as well as in photographic chemicals, hydraulic brake fluids and lubricants, disinfectants, pickling solutions and perfumes (Dentan et al. 2000).

Releases to the Environment

According to information reported under section 71 of CEPA 1999, less than 100 kg of 2‑methoxypropanol was released into the environment in 2006, mainly to air (Environment Canada c2008). Releases of 2-methoxypropanol and PGME are not included on the National Pollutant Release Inventory (NPRI 2006) or the US Toxics Release Inventory (TRI 2006).

Environmental Fate

Level III fugacity modelling was performed for 2-methoxypropanol based on its physical and chemical properties (Table 2), and the results are summarized in Table 3. The results indicate that 2-methoxypropanol is expected to partition predominantly to soil when it is released to air or soil. When it is released to water, most of it remains in this compartment;; however, some is expected to partition to sediments.

Table 3. Results of the Level III fugacity modelling (EQC 2003) for 2-methoxypropanol

  Fraction of substance partitioning to each medium (%)
Substance released to Air Water Soil Sediment
Air (100%)

1.98

5.87

88.6

3.58

Water (100%)

2.47E-10

62.1

1.1E-08

37.9

Soil (100%)

3.95E-11

0.010

100

0.006

Persistence and Bioaccumulation Potential

Environmental Persistence

Environmental persistence was determined based on modelled data, as indicated in Table 4.

Table 4. Modelled data for persistence of 2-methoxypropanol in the environment

Fate process Degradation
value
Endpoint
(Units)
Reference
Oxidation in air 0.54 t1/2 (days)

AOPWIN 2000

Biodegradation in water 15

BIOWIN 2000 (Ultimate Survey Model)

0.77 Probability

BIOWIN 2000 (MITI Non-Linear Model)

Abbreviations: MITI, Ministry of International Trade & Industry, Japan; t½, half-life.

2-Methoxypropanol does not undergo direct photolysis. As is the case for other glycol ethers, it does not absorb ultraviolet radiation within the solar spectrum. However, it is expected to react with photochemically produced hydroxyl radicals in the atmosphere. As a result, the estimated half-life in the atmosphere is in the order of 0.54 day (Table 4). Due to its high water solubility, wet deposition may occur during precipitation events; however, due to its short atmospheric residence time, this process is not expected to be of major importance to the atmospheric fate of 2-methoxypropanol.

2-Methoxypropanol is completely miscible in water. Its low Henry’s Law constant indicates that significant volatilization from water is not expected. Based upon its chemical structure, hydrolysis is not expected to be an important removal process in the environment (EURAR 2006).

Biodegradation data in water are not available for 2-methoxypropanol; however, several aerobic biodegradation studies of PGME have shown that this compound is readily biodegradable in most cases (EURAR 2006).

The weight of evidence based on the above-described data indicates that 2-methoxypropanol does not meet the persistence criteria for air (half-life ≥ 2 days), water and soil (half-lives ≥ 182 days) or sediment (half-life ≥ 365 days) as set out in the Persistence and Bioaccumulation Regulations (Canada 2000).

Potential for Bioaccumulation

Modelled data for the bioaccumulation potential of 2-methoxypropanol in fish are summarized in Table 5. The results indicate that this chemical is not expected to bioaccumulate in the environment.

Table 5. Modelled data for bioaccumulation for 2-methoxypropanol in fish

Endpoint

Value
(L/kg wet weight)

Reference
BAF 0.96

Arnot and Gobas 2003 (Gobas BAF T2MTL)

BCF 1.0

Arnot and Gobas 2003 (Gobas BCF 5% T2LTL)

1.0

ACD 2007

10

OASIS Forecast 2005

3.2

BCFWIN 2000

The Modified Gobas BAF middle trophic level model for fish produced a bioaccumulation factor (BAF) of 0.96 L/kg wet weight, indicating that this substance is not likely to bioconcentrate or biomagnify in the environment. The bioconcentration factor (BCF) models also provide a weight of evidence to support the low bioconcentration potential of the substance.

Weight of evidence indicates that 2-methoxypropanol does not meetthe bioaccumulation criteria (BCF, BAF ≥ 5000) as set out in the Persistence and Bioaccumulation Regulations (Canada 2000).

Potential to Cause Ecological Harm

As indicated above, 2-methoxypropanol does not meet the persistence or bioaccumulation criteria as set out in the Persistence and Bioaccumulation Regulations (Canada 2000).

As noted below in the exposure assessment section for human health, environmental concentrations of 2-methoxypropanol are expected to be low. Reported releases from facilities in Canada are less than 100 kg/year, predominantly to air (Environment Canada 2008). Atmospheric releases of the substance from finished products containing the substance would be diffuse, from a large number of small sources rather than from a few large point sources, so the resulting concentrations of 2-methoxypropanol in air would be low. Based on conservative assumptions, concentrations in water resulting from aquatic releases would not be high enough to harm sensitive aquatic organisms.

Table 6 summarizes the modelled data for aquatic toxicity of 2-methoxypropanol. None of the results were below 1.0 mg/L, suggesting that this substance does not exhibit high acute toxicity and would not be expected to cause harm to aquatic organisms at relatively low concentrations.

Table 6. Modelled data for aquatic toxicity

Test organism Type of test Endpoint Value
(mg/L)
Reference

Green alga

Chronic

96-h MATC

170

ECOSAR 2004

96-h EC50

7 153

Earthworm

Subacute

14-d LC50

3 242

ECOSAR 2004

Daphnia magna

Acute

48-h EC50

19 000

TOPKAT 2004

Daphnid

Subacute

16-d EC50

228

ECOSAR 2004

Acute

48-h EC50

13 205

Mysid shrimp

Acute

96-h LC50

24 965

ECOSAR 2004

Fathead minnow, Pimephales promelas

Acute

96-h LC50

16 500

TOPKAT 2004

4 998

AIES 2003-–2005

183 537

OASIS Forecast 2005

Fish

Subacute

30-d MATC

1 262

ECOSAR 2004

Acute

14-d LC50

17 850

96-h LC50

1 006

96-h LC50

14 637

Abbreviations: EC50, concentration affecting 50% of the test population; LC50, lethal concentration affecting 50% of the test population; MATC, maximum acceptable toxicant concentration.

cBased on the information available, 2-methoxypropanol is unlikely to cause ecological harm in Canada.

Uncertainties in Evaluation of Ecological Risk

Quantitative structure–activity relationship (QSAR) models were used to estimate persistence and bioaccumulation. There are uncertainties associated with the use of these models to estimate ecological risk. In addition, the value for Kow, which is used as input to the QSAR models, was also estimated.

There is uncertainty about environmental exposure, but releases of 2-methoxypropanol are low and the substance is not expected to be persistent; therefore, environmental concentrations are likely to be low.

Potential to Cause Harm to Human Health

Exposure Assessment

Multimedia intake estimates were not derived in this assessment due to insufficient available data. No data were identified on concentrations of 2-methoxypropanol in environmental media in Canada or elsewhere. 1-Methoxy-2-propanol (alpha isomer of PGME) was identified in indoor air in three European studies (De Bortoli et al. 1986; Plieninger and Marchl 1999; Schleibinger et al. 2001). The maximum indoor air concentrations for the three studies ranged from 60 to 2570 µg/m3 (De Bortoli et al. 1986; Plieninger and Marchl 1999; Schleibinger et al. 2001), the highest concentrations being measured in Germany (Schleibinger et al. 2001). Taking into account that 2-methoxypropanol may be co-present with 1-methoxy-2-propanol in indoor air at concentrations as high as 5% of PGME (Verschueren 2001), a conservative estimate of the maximum potential concentration of 2-methoxypropanol in indoor air would range from 3 to 135 µg/m3.

Modelled predictions of concentrations of 2-methoxypropanol in environmental media, based on the industrial releases reported under section 71 of CEPA 1999 (Environment Canada c2008), were very low, and population exposure is therefore expected to be negligible (ChemCAN 2003). 1-Methoxy-2-propanol was detected, but not quantified, in mussels collected near Japan (HSDB 2005). 1-Methoxy-2-propanol was also measured in soft raw goat milk cheese during ripening in France at a maximum concentration of 22 ng/g of cheese on day 38; however, this concentration had decreased to 7 ng/g by day 43 (Sablé et al. 1997). Concentrations of 2-methoxypropanol in food and beverages are not expected to be significant, based on available information on uses and on physical and chemical properties and since the potential for 2-methoxypropanol to bioaccumulate is low.

Based on the available information, 2-methoxypropanol may be present as an impurity in the following consumer products that contain PGME: nail enamel, nail polish remover, hair conditioner, hair spray, hair dye, false eyelash adhesive and remover (CNS 2008), paint remover, spray stain remover, concrete floor primer and polyurethane varnish (HPD 2008), as well as in aerosol paint and exterior stain (Environment Canada c2008). Scenarios in ConsExpo version 4.1 (ConsExpo 2006) were used to estimate inhalation and dermal exposures to 2-methoxypropanol during use of these products, and the results are presented in Appendix 1. As the consumer products for which data are available are used primarily by adults, the estimates of exposure have been derived for adults only. The exact concentration of 2-methoxypropanol in PGME is unknown for most consumer products but may range from less than 0.5% to as high as 5% (Hellwig et al. 1994; Verschueren 2001; CHEMINFO 2007). Actual 2-methoxypropanol concentrations were available for the exterior stain and aerosol paint products (Environment Canada 2008). For all other products, a concentration of 2% 2-methoxypropanol in PGME, identified from a Material Safety Data Sheet (J.T. Baker 2006), was assumed.

The US Household Products Database (HPD 2007) lists two plaster-type products containing 2-methoxypropanol; however, their use in Canada is not confirmed, and more current Material Safety Data Sheets for these two specific products indicate that 2-methoxypropanol is no longer present in these products (Red Devil 2004, 2006). Products listed in the Household Products Database as containing PGME may also contain 2-methoxypropanol as an impurity (HPD 2008). Of those listed, only paint remover, concrete floor primer, polyurethane varnish, paint stripper, wallpaper remover and spot remover had current Material Safety Data Sheets confirming the presence of PGME. However, except for the paint remover, concrete floor primer, polyurethane varnish and spot remover, which have been confirmed to be accessible to consumers in Canada, the potential availability of these particular products in Canada is unknown.

Predicted airborne concentrations during use of various consumer products ranged from 0.01 to 51 700 µg/m3. The highest predicted airborne concentration was from use of paint remover (solvent-based), assuming a concentration of 0.26% 2-methoxypropanol (based on a maximum concentration of 13% PGME in paint remover containing 2% 2-methoxypropanol as an impurity) (Grainger 2006; J.T. Baker 2006). Airborne concentrations from use of paint remover (water-based), concrete floor primer, polyurethane varnish (applied to floors), nail polish remover and nail enamel were greater than 1000 µg/m3. The predicted airborne concentrations would range from less than 0.1 to 12 900 µg/m3 and from less than 0.1 to 129 000 µg/m3 if PGME contained 0.5% and 5% 2-methoxypropanol, respectively. The predicted concentration in air was not estimated for external stains, as ConsExpo does not have a model to calculate outdoor inhalation exposures to consumer products. Weather conditions, which can be highly variable and affect ventilation rate as well as temperature, and an undefined room volume (infinitely large) prevent the quantification of reasonable outdoor inhalation exposures (RIVM 2007a).

Dermal contact with 2-methoxypropanol, found as an impurity in PGME-containing products, could significantly contribute to overall exposures to this substance, as data indicate that PGME can be readily absorbed through human skin in vitro (Larese Filon et al. 1999). Estimated dermal exposures for products used infrequently (paint remover, concrete floor primer, polyurethane varnish, aerosol paint, exterior stain) ranged from 0.03 to 59 µg/kg body weight (kg-bw) per event, whereas estimated dermal exposures from personal care products and spray spot remover ranged from 3.1 to 2820 µg/kg-bw per day as an acute dose per event and from 1 to 77 µg/kg-bw per day if amortized to chronic exposures for products used more frequently (see Appendix 1). The highest predicted dermal exposure was from use of hair dye, which assumed a concentration of 0.2% 2-methoxypropanol (based on a maximum concentration of 10% PGME in hair dye containing 2% 2-methoxypropanol as an impurity) (J.T. Baker 2006; CNS 2008). The ConsExpo software did not have a specific scenario for exterior stain.1 The estimated dermal exposures would range between 0.008 and 705 µg/kg-bw per event and between 0.08 and 7050 µg/kg-bw per event if PGME contained 0.5% and 5% 2-methoxypropanol, respectively.

1-Methoxy-2-propanol has been identified in emissions from new computer monitors at 13 µg/unit per hour after 7 h of operation. No emissions were measured after 9 days of operation (Danish Technological Institute 2003). 2-Methoxypropanol was not measured in this study.

No data were identified on concentrations of 2-methoxypropanol in the general environment or in food in Canada or elsewhere. Indoor air data for 1-methoxy-2-propanol were identified in Europe and used as a surrogate for estimation of indoor air concentrations of 2-methoxypropanol in Canada. Although there is some uncertainty in using this method, it is very likely that the value used overestimates actual exposures to 2-methoxypropanol, since a concentration of 5% 2-methoxypropanol in PGME was assumed. There is confidence that exposures to 2-methoxypropanol from the general environment are very low based on the fact that this substance is not produced commercially but is only present as an impurity in PGME and based on its physical and chemical properties, release information and use pattern. There is low confidence in the modelled estimates of exposure during use of consumer products, as there is some uncertainty on the levels of 2-methoxypropanol in various products that contain PGME and on the presence of PGME-containing products in Canada, and since no appropriate inhalation scenario was available to estimate exposure to exterior stains.

Health Effects Assessment

The available health effects information for 2-methoxypropanol is summarized in Appendix 2. In light of the very limited available database on 2-methoxypropanol, data on its acetate moiety (2-methoxypropanol acetate), which is rapidly hydrolyzed to 2-methoxypropanol via esterases in the body (DECOS 1993; ECETOC 2005a), and its principal metabolite, 2‑methoxypropanoic acid, are considered relevant to this assessment. Studies involving PGME, which consists of 1-methoxy-2-propanol (≥ 95%) and 2-methoxypropanol £ (≤5%, as an impurity), are considered to have more limited relevance to evaluation of the toxicity of the latter substance.

The European Commission has classified 2-methoxypropanol as a Category 2 substance with Risk Phrase R61 (“May cause harm to the unborn child”) (European Commission 1997, 1998; ECB 2004; ESIS 2007). This classification was based on observed dose-related developmental effects in rabbits following inhalation exposure to 2-methoxypropanol during the organogenesis period (ECB 2004). In this study, dose-related, significantly increased fetal resorption and incidence of fetal visceral and skeletal malformations/variations and significantly reduced fetal body weights were observed at 225 parts per million (ppm) (843 mg/m3) and above, in the absence of maternal toxicity. No exposure‑related effects were observed at 145 ppm (543 mg/m3), the no-observed-effect concentration (NOEC). Maternal toxicity, evidenced by significantly reduced body weights and increased absolute placental weights, was observed at 545 ppm (2040 mg/m3). Although significantly decreased absolute uterine weights were observed at lower concentrations, the authors speculated that it was at least partially related to the low number and weights of fetuses (BASF 1988b; Hellwig et al. 1994). Pregnant rats exposed to higher concentrations of 2-methoxypropanol (1000–3000 ppm, equivalent to 3745–11 235 mg/m3) had fetuses with thoracic vertebral incisions and split vertebrae (BASF 1986).

In addition, when pregnant rats and rabbits were exposed to 2-methoxypropanol acetate by inhalation, similar developmental effects, such as significantly increased fetal resorption, thoracic vertebral incision and split vertebrae (rats, at 2700 ppm, equivalent to 10 112 mg 2-methoxypropanol/m3, the highest concentration tested), and malformations of sternum, paws, major blood vessels and heart (rabbits, at 550 ppm, equivalent to 2060 mg 2-methoxypropanol/m3, the highest concentration tested) were observed. Effects in dams included significantly reduced maternal body weights, respiratory and eye irritation and sedation in rats (at 550 ppm and above) and slight but statistically significant reductions in maternal body weights in rabbits (at 550 ppm). Furthermore, rabbits appeared to be more sensitive than rats in this study; all fetuses of rabbits exposed to 550 ppm 2-methoxypropanol acetate showed severe cardiac and skeletal abnormalities, whereas rats exposed to 2700 ppm 2-methoxypropanol acetate showed only some skeletal variations (Merkle et al. 1987). It was speculated that this species difference is due to the slower excretion rate of 2-methoxypropanol or 2-methoxypropanol acetate in rabbits (ECETOC 2005a).

No dermal study conducted with 2-methoxypropanol was identified. Dermal application of its acetate moiety, 2-methoxypropanol acetate, at doses up to 2000 mg/kg-bw per day during gestation days 6–18 did not elicit developmental or maternal toxicity in rabbits (Merkle et al. 1987). However, it is recognized that the acetate may be absorbed through the skin to a lesser extent than 2‑methoxypropanol (Larese Filon et al. 1999). 

No information on potential developmental toxicity via oral administration of 2‑methoxypropanol was identified. It is recognized that 2-methoxypropanoic acid is the putatively developmentally toxic metabolite of 2-methoxypropanol (ECETOC 2005a). Pregnant rabbits were administered 2-methoxypropanoic acid via gavage during gestation days 7–19, followed by evaluation on day 28. Significantly increased fetal resorption and incidence of fetal variations and malformations, such as missing ribs, delayed ossifications, retrocaval ureter and paraovarian cyst, were observed at 78 mg 2-methoxypropanoic acid/kg‑bw per day (equivalent to 67.6 mg 2-methoxypropanol/kg-bw per day, based on same molar amount conversion), with a no-observed-(adverse-)effect level (NO(A)EL) of 26 mg/kg-bw per day (equivalent to 22.5 mg 2-methoxypropanol/kg-bw per day). The authors speculated that 100% of the 2‑methoxypropanol in the blood was converted to 2-methoxypropanoic acid (Carney et al. 2003).

Although no reproductive toxicity studies involving exposure to 2-methoxypropanol were identified, testicular effects were observed in a three-generation study in rats administered two PGME commercial products, which contained 0.5–1.5% 2-methoxypropanol and 99.5–98.5% 1‑methoxy-2-propanol, respectively, in drinking water during the gametogenesis cycle (64 days for males and 15 days for females). Sperm counts in epididymis decreased significantly in the first generation as the proportion of 2-methoxypropanol in the test substance increased. No significant effects were observed in epididymis or testes in the subsequent two generations. No variations in estradiol or testosterone concentration were observed in the first and second generations. No further analyses on the female reproductive system were performed in the study. A NO(A)EL for 2‑methoxypropanol of 11.5 mg/kg-bw per day was identified for testicular toxicity  (Lemazurier et al. 2005). Effects on testes weights or histology were not observed in male rats after 10 days of oral (gavage) or 28 days of inhalation exposure to 2-methoxypropanol or its acetate at higher dose levels, in studies described below (Ma-Hock et al. 2005).

Hematological effects, evidenced by marginal reduction in red blood cell counts and total hemoglobin concentration, but without bone marrow damage, were observed in male rats following oral exposure to 1800 mg 2-methoxypropanol/kg-bw per day or 2600 mg 2-methoxypropanol acetate/kg‑bw per day (equivalent to 1772 mg 2‑methoxypropanol/kg-bw per day) via gavage for 10 days (BASF 1982; Ma-Hock et al. 2005). In addition, hematological and biochemical alterations (no statistical analysis available), such as reduced blood glucose level and increased thromboplastin time in males and reduced urea and protein levels and increased polyphosphatase levels in females, were observed in rats exposed via inhalation to 2-methoxypropanol acetate at concentrations up to 2800 ppm (10 486 mg 2-methoxypropanol/m3) for 28 days. Thymus atrophy as well as reduced body weight gain and respiratory irritation were also observed at this concentration (Ma-Hock et al. 2005).

With regard to the potential carcinogenicity or chronic toxicity of 2-methoxypropanol, no long-term study has been identified for the pure substance. Rats and mice were exposed to commercial PGME products, which contained 97.39–97.49% 1‑methoxy‑2‑propanol and 2.46–2.59% 2-methoxypropanol, by inhalation up to 3000 ppm (about 281–292 mg 2-methoxypropanol/m3) for 2 years. Significantly increased incidence of kidney adenomas was observed in male rats, which was associated with α2u-globulin nephropathy (Spencer et al. 2002). Only limited data are available on the genotoxicity of 2-methoxypropanol. It did not induce gene mutation in Ames tests with various Salmonella strains, with or without metabolic activation (BASF 1988a).

The confidence in the toxicity dataset associated with 2-methoxypropanol exposure, particularly by inhalation, is considered to be moderate, as the limited data on this substance are supported by data on its acetate analogue and its principal metabolite. However, the database on the effects of dermal exposure to 2-methoxypropanol is much more limited; extrapolation of results of studies with the acetate moiety may not be appropriate, due to differences in absorption. There is uncertainty regarding the neoplastic potential of 2-methoxypropanol, due to a lack of appropriate long-term animal study data for this substance. Although the studies conducted with PGME commercial products reported only renal tumours in rats, which are associated with a male rat specific etiology, it is noted that very low levels of 2-methoxypropanol were administered to rats in these studies. However, putative carcinogenicity of 2-methoxypropanol was not predicted by computer-based quantitative or non-quantitative structure–activity relationship (QSAR/SAR) models (CASETOX version 1.8 [CASETOX 2006]; TOPKAT version 6.2 [TOPKAT 2004]; DEREK version 8.01 [DEREK 2004]). As well, 2-methoxypropanol did not induce gene mutation in bacteria (BASF 1988a).

Characterization of Risk to Human Health

Based principally on the weight of evidence–based classification of 2-methoxypropanol by the European Commission as Category 2 for developmental toxicity (ESIS 2007) and consideration of available relevant data for the substance as well as for related chemicals, the critical effect for characterization of risk to human health for 2-methoxypropanol is developmental toxicity. In addition, effects on blood and male reproductive systems were observed in experimental animals. Therefore, margins of exposure are derived between lowest exposure levels associated with induction of these effects and conservative estimates of population exposure to 2-methoxypropanol.

The principal source of exposure to 2-methoxypropanol for the general population is expected to be through inhalation and dermal contact during use of consumer products containing the substance. The maximum potential indoor air concentration of 2‑methoxypropanol, based on monitoring data for 1-methoxy-2-propanol collected in Germany (Schleibinger et al. 2001), and assuming that 2‑methoxypropanol is co-present with 1-methoxy-2-propanol in indoor air at a maximum concentration of 5% of PGME, is 135 mg/m3. Modelling-based estimates of inhalation exposure during use of cosmetic or paint products resulted in much higher indoor air concentrations. The conservative upper-bounding estimate of airborne concentration is 52 mg/m3 from use of paint remover. Comparison between the critical lowest-observed-effect concentration (LOEC) of 843 mg/m3 for developmental effects observed in experimental animals (Hellwig et al. 1994) and the estimated maximum indoor air concentration of 135 µg/m3 results in a large margin of exposure of approximately 6200. However, the margins of exposure to 2-methoxypropanol in air during use of consumer products containing the substance are much smaller (e.g., approximately 16 for use of paint remover). The margins of exposure for use of multiple products within a short period of time would be greater than those for use of individual products (e.g., nail polish remover and nail enamel applied in 1 day). Thus, the margins for inhalation exposure during use of certain consumer products (such as paint remover, some personal care products, concrete floor primer, polyurethane varnish) may not be adequately protective to human health in light of the uncertainties in the databases and the serious nature of the health effects associated with exposure to this substance (i.e., developmental toxicity).

Dermal contact also contributes significantly to exposure to 2-methoxypropanol during use of products containing the substance, with the highest predicted acute dermal dose of 2820 µg/kg-bw per event from hair dye. However, no adequate dermal toxicity study has been identified for 2-methoxypropanol to provide a basis for dose–response analysis for comparison with this estimated exposure. (Although one study involving dermal exposure to 2-methoxypropanol acetate was available, due to differences in skin permeability of the two substances [Larese Filon et al. 1999], it is not considered appropriate to extrapolate the results of this study to quantify hazard for 2-methoxypropanol.) Therefore, insufficient information is available to characterize risk to health associated with dermal exposure to 2-methoxypropanol from consumer products.

Uncertainties in Evaluation of Risk to Human Health

Data were inadequate to permit quantification of exposure to 2-methoxypropanol from environmental media in Canada; however, the available information on releases in Canada, its physical and chemical properties and the absence of commercial production in Canada indicate that concentrations in these media are likely to be negligible. Although it is present as an impurity in PGME, which is a high production volume chemical, the estimated indoor air concentration of 2-methoxypropanol derived from PGME measurements in European studies likely overestimates actual exposures of the general population in Canada based on the conservative assumptions used (i.e., that 2-methoxypropanol could be present in PGME at the maximum possible concentration of 5%). Although there is uncertainty due to the limited information on the presence or concentrations of the substance in products available in Canada, the estimates of exposure from the use of consumer products containing 2-methoxypropanol were based on conservative assumptions (including the assumption of the proportion of 2-methoxypropanol present as an impurity in PGME in products) and may overestimate actual exposures. If the actual concentrations of 2-methoxypropanol in PGME in the consumer products are at 0.5% or less, the exposure estimates from use of these consumer products would be lower.

There is also some uncertainty associated with the potential exposures from the use of multiple products containing 2-methoxypropanol within a short period of time. There is some uncertainty regarding the differences in sensitivity between experimental animals and humans in view of the paucity of epidemiological data, although the critical effects observed in laboratory studies are considered likely relevant to humans, as they are consistent with those reported for other glycol ethers. In addition, there is uncertainty with respect to the carcinogenicity of 2-methoxypropanol due to a lack of appropriate long‑term studies, although the available information from in vitro genotoxicity tests, inhalation studies with commercial PGME products and (Q)SAR predictions does not give cause for concern. As well, there is uncertainty with regard to the potential of 2-methoxypropanol to induce effects by dermal contact. Although the limited available data for its acetate moiety suggest low toxicity by this route, it is recognized that there may be differences in rates of absorption between the two substances, which may influence relative potency.

Conclusion

Based upon the potential inadequacy of the margins of exposure between conservative estimates of exposure to 2-methoxypropanol during use of consumer products by inhalation and critical effect levels for developmental toxicity in experimental animals, it is concluded that 2‑methoxypropanol should be considered “toxic” as defined in paragraph 64(c) of CEPA 1999—i.e., as a substance that may be 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 presented in this screening assessment, it is concluded that 2-methoxypropanol is not entering the environment in a quantity or concentration or under conditions that have or may have an immediate or long-term effect on the environment or its biological diversity or that constitute or may constitute a danger to the environment on which life depends.

It is therefore concluded that 2-methoxypropanol be considered to be a substance that may enter the environment in a quantity or concentration or under conditions that constitute or may constitute a danger in Canada to human life or health. Additionally, 2-methoxypropanol does not meet the criteria for persistence and bioaccumulation potential as set out in the Persistence and Bioaccumulation Regulations (Canada 2000).

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Appendix 1. Estimated exposures to 2-methoxypropanol in consumer products1 based on ConsExpo version 4.1 (ConsExpo 2006)

Consumer
product scenarios

Assumptions1

Estimated exposure

Nail polish remover

Weight fraction of 2-methoxypropanol: 0.6%—based on maximum concentration of 30% PGME in nail polish remover (CNS 2008) containing 2% 2-methoxypropanol as an impurity (J.T. Baker 2006)

Inhalation: Evaporation from a constant surface
Exposure duration of 5 min, product amount of 0.5 g, breathing space of 1 m3 (application occurs close to face), ventilation rate of 1/h, release area of 25 cm2, application duration of 5 min, temperature of 20ºC, use Langmuir’s method for mass transfer rate (solvent-based product), molecular weight matrix of 75 g/mol (RIVM 2006a)

Dermal absorption: Exposure, instant application
Exposed area of 11 cm2, amount upon skin of 0.2 g, frequency of 156×/year (RIVM 2006a)

Inhalation – Mean event concentration
2800 µg/m3

 

Dermal – Acute applied dose
17 µg/kg-bw per event

 

Dermal – Chronic dose
7.2 µg/kg-bw per day

Nail enamel

Weight fraction of 2-methoxypropanol: 0.6%—based on maximum concentration of 30% PGME in nail enamel (CNS 2008) containing 2% 2-methoxypropanol as an impurity (J.T. Baker 2006)

Inhalation: Evaporation from a constant surface
Exposure duration of 5 min, product amount of 0.25 g, breathing space of 1 m3 (application occurs close to face), ventilation rate of 1/h, release area of 19 cm2, application duration of 5 min, temperature of 20ºC, use Langmuir’s method for mass transfer rate, molecular weight matrix of 124 g/mol, uptake fraction of 1 (RIVM 2006a)

Dermal absorption: Exposure, instant application
Exposed area of 4 cm2, amount upon skin of 0.05 g, frequency of 156×/year (RIVM 2006a)

Inhalation – Mean event concentration
1430 µg/m3

 

Dermal – Acute applied dose
4.2 µg/kg-bw per event

 

Dermal – Chronic applied dose
1.8 µg/kg-bw per day

Hair spray

Weight fraction of 2-methoxypropanol: 0.2%—based on maximum concentration of 10% PGME in hair spray (CNS 2008) containing 2% 2-methoxypropanol as an impurity (J.T. Baker 2006)

Inhalation: Exposure to spray – spraying towards exposed person
Spray duration of 0.24 min, exposure duration of 5 min, room volume of 10 m3, room height of 2.5 m, ventilation rate of 2/h, cloud volume of 0.0625 m3, mass generation rate of 0.47 g/s, airborne fraction of 1 g/g, weight fraction non-volatile of 0.03 g/g, density non-volatile of 1.5 g/cm3, initial particle distribution median (coefficient of variation) of 35 µm, inhalation cut-off diameter of 15 µm (RIVM 2006a)

Dermal absorption: Exposure, instant application
Exposed area of 565 cm2, amount applied of 0.6 g, frequency of 438×/year (RIVM 2006a)

Inhalation – Mean event concentration
2.8 µg/m3

 

Dermal – Acute applied dose
17 µg/kg-bw per event

 

Dermal – Chronic applied dose
20 µg/kg-bw per day

Hair conditioner (leave-on product for hair setting in gel format [CNS 2008])2 ;

Weight fraction of 2-methoxypropanol: 0.2%—based on maximum concentration of 10% PGME in hair conditioner (CNS 2008) containing 2% 2-methoxypropanol as an impurity (J.T. Baker 2006)

Inhalation: not considered for this scenario according to the ConsExpo software (RIVM 2006a)

Dermal absorption: Exposure, instant application
Exposed area of 580 cm2, applied amount of 0.3 g (RIVM 2006a), frequency of 104×/year

Dermal – Acute applied dose
8.4 µg/kg-bw per event

 

Dermal – Chronic applied dose
2.4 µg/kg-bw per day

Hair dye (permanent hair dye)

Weight fraction of 2-methoxypropanol: 0.2%—based on maximum concentration of 10% PGME in hair dye (CNS 2008) containing 2% 2-methoxypropanol as an impurity (J.T. Baker 2006)

Inhalation: not considered for this scenario according to the ConsExpo software (RIVM 2006a)

Dermal absorption: Exposure, instant application
Exposed area of 580 cm2, applied amount of 100 g (RIVM 2006a), frequency of 10×/year

Dermal – Acute applied dose
2820 µg/kg-bw per event

 

Dermal – Chronic applied dose
77 µg/kg-bw per day

 Spray spot remover (use spray spot remover, laundry pre-treatment)

Weight fraction of 2-methoxypropanol: 0.c1%—based on maximum concentration of 5% PGME in spot remover (Harris Research Inc. 2008) containing 2% 2-methoxypropanol as an impurity (J.T. Baker 2006)

Phase 1: Spraying
Inhalation: Spray Model
Spray duration of 0.05 min, exposure duration of 10 min, room volume of 10 m3, room height of 2.5 m, ventilation rate of 2/h, mass generation rate of 1.5 g/s, airborne fraction of 0.2 g/g, weight fraction non-volatile of 0.1 g/g, density non-volatile of 1.8 g/cm3, initial particle distribution median of 100 µm, inhalation cut-off diameter of 15 µm (RIVM 2006b)

Dermal: Constant rate
Contact rate of 46 mg/min, release duration of 0.05 min, frequency of 128×/year (RIVM 2006b)

Phase 2: Washing
Inhalation: not considered for this scenario according to the ConsExpo software (RIVM 2006b)

Dermal: Instant application
Exposed area of 430 cm2, weight fraction must be multiplied by 0.1 to account for dilution (0.1 × 0.001 = 0.0001), diluted product amount of 2 g, frequency of 128×/year (RIVM 2006b)

Inhalation – Mean event concentration
0.01 µg/m3

 

Dermal – Acute applied dose
0.032 µg/kg-bw per event

 

Dermal – Chronic applied dose
0.011 µg/kg-bw per day

 

Dermal – Acute applied dose
2.8 µg/kg-bw per event

 

Dermal – Chronic applied dose
1 µg/kg-bw per day

Graffiti and spray paint remover: solvent-based (use paint remover scenario)

Weight fraction of 2-methoxypropanol: 0.c26%—based on maximum concentration of 13% PGME in paint remover (Grainger 2007) containing 2% 2-methoxypropanol as an impurity (J.T. Baker 2006)

Inhalation: Evaporation from increasing area
Exposure and application duration of 60 min, product amount of 1000 g, room volume of 20 m3, ventilation rate of 0.6/h, release area of 2 m2, temperature of 20ºC (RIVM 2007a), use Langmuir method for mass transfer rate as product is solvent-based, molecular weight matrix of 3000 g/mol (for solvent-rich paint-like product) (RIVM 2007b)

Dermal: Instant application
Surface area of 430 cm2, product amount of 0.5 g (RIVM 2007a)

Inhalation – Mean event concentration
51 700 µg/m3

 

Dermal – Acute applied dose
18.3 µg/kg-bw per event

Graffiti and spray paint remover: water-based (use paint remover scenario)

Weight fraction of 2-methoxypropanol: 0.c26%—based on maximum concentration of 13% PGME in paint remover (Grainger 2006) containing 2% 2-methoxypropanol as an impurity (J.T. Baker 2006)

Inhalation: Evaporation from increasing area
Exposure and application duration of 60 min, product amount of 1000 g, room volume of 20 m3, ventilation rate of 0.6/h, release area of 2 m2, temperature of 20ºC (RIVM 2007a), use Thibodeaux method for mass transfer rate as product is waterborne, molecular weight matrix of 120 g/mol (for waterborne paint-like product) (RIVM 2007b)

Dermal: Instant application
Surface area of 430 cm2, product amount of 0.5 g (RIVM 2007a)

Inhalation – Mean event concentration
12 400 µg/m3

 

Dermal – Acute applied dose
18.3 µg/kg-bw per event

Concrete floor primer (use general coating scenario – coating of a floor in a garage)

Weight fraction of 2-methoxypropanol: 0.1%—based on maximum concentration of 5% PGME in concrete floor primer (BASF Building Systems 2006) containing 2% 2-methoxypropanol as an impurity (J.T. Baker 2006)

Inhalation: Evaporation from increasing area
Exposure and application duration of 60 min, product amount of 3 kg, room volume of 34 m3, ventilation rate of 1.5/h, release area of 15 m2, temperature of 15ºC (RIVM 2007a), use Thibodeaux method for mass transfer rate as product is waterborne, molecular weight matrix of 45 g/mol (for waterborne paint-like product) (RIVM 2007b)

Dermal: Instant application
Surface area of 108 cm2, product amount of 0.25 g (RIVM 2007a)

Inhalation – Mean event concentration
4240 µg/m3

 

Dermal – Acute applied dose
3.5 µg/kg-bw per event

Waterborne polyurethane varnish (use waterborne paint scenario – assume varnishing wood floor in living room)

Weight fraction of 2-methoxypropanol: 0.06%—based on maximum concentration of 3% PGME in waterborne polyurethane varnish (Sherwin-Williams 2008a) containing 2% 2-methoxypropanol as an impurity (J.T. Baker 2006)

Inhalation: Evaporation from increasing area
Exposure duration of 132 min, application duration of 120 min, molecular weight matrix of 45 g/mol (for waterborne paint-like product), use Thibodeaux method for mass transfer rate as product is waterborne (RIVM 2007b), room volume of 58 m3 (living room), release area of 22 m2 (living room) (RIVM 2006c), ventilation rate of 1/h (US EPA 1986), applied amount of 2060 g calculated based on release area of 22 m2, coverage of 0.011 m2/cm3 (450 ft2/gal) (midrange between 400 and 500 ft2/gal) (Sherwin-Williams 2008b) and a product density  of 1.03 g/cm3 (Sherwin-Williams 2008b)

Dermal: Constant rate
Contact rate of 8 mg/min (water-based wood preservative), release duration of 120 min (same as application duration) (RIVM 2007b)

Inhalation – Mean event concentration
2370 µg/m3

 

Dermal – Acute applied dose
8.1 µg/kg-bw per event

Waterborne polyurethane varnish (use waterborne paint scenario – assume varnishing a table)

Weight fraction of 2-methoxypropanol: 0.06%—based on maximum concentration of 3% PGME in waterborne polyurethane varnish (Sherwin-Williams 2008a) containing 2% 2-methoxypropanol as an impurity (J.T. Baker 2006)

Inhalation: Evaporation from increasing area
Applied amount of 150 g, ventilation rate of 1/h, release area of 2.5 m2, application duration of 28 min (US EPA 1986), exposure duration of 31 min (28 min × 1.1; RIVM 2007b), molecular weight matrix of 45 g/mol (for waterborne paint-like product), use Thibodeaux method for mass transfer rate as product is waterborne (RIVM 2007b), room volume of 20 m2 (unspecified room) (RIVM 2006c)

Dermal: Constant rate
Contact rate of 8 mg/min (water-based wood preservative), release duration of 28 min (same as application duration) (RIVM 2007b)

Inhalation – Mean event concentration
720 µg/m3

 

Dermal – Acute applied dose
0.032 µg/kg-bw per event

Aerosol paint (spray can of 400 ml, to paint a radiator in a garage; the garage is left 5 min after spraying)

Weight fraction of 2-methoxypropanol: 0.001% (Environment Canada 2008)

Inhalation: Exposure to spray
Exposure duration of 20 min, room volume of 34 m3, ventilation rate of 1.5/h, mass generation rate of 0.33 g/s, spray duration of 15 min, airborne fraction of 1, density non-volatile of 1.5 g/cm3, weight fraction non-volatile of 0.3 g/cm3, room height of 2.25 m, inhalation cut-off diameter of 15 µm, non-respirable uptake fraction of 1; it was assumed that spraying was away from exposed person (RIVM 2007b)

Dermal absorption: Direct dermal contact with product – constant rate
Contact rate of 100 mg/min, release duration of 15 min (RIVM 2007b)

Inhalation – Mean event concentration
3.8 µg/m3

 

Dermal – Acute applied dose
0.21 µg/kg-bw per event

Exterior stain (general coating – assume that the exterior surface coated has equivalent surface area to the floor of a garage)

Weight fraction of 2-methoxypropanol: 0.117% (Environment Canada 2008)

Inhalation: exterior paint, therefore inhalation is not considered3

Dermal absorption: Exposure, instant application
Surface area of 108 cm2, product amount of 0.25 g (RIVM 2007a)

Dermal – Acute applied dose
4.1 µg/kg-bw per event

Exterior stain (solvent-rich paint –
assume brushing or rolling of a wooden lathed exterior wall)

Weight fraction of 2-methoxypropanol: 0.117% (Environment Canada 2008)

Inhalation: exterior paint, therefore inhalation is not considered3

Dermal absorption: Direct dermal contact with product –constant rate
Contact rate of 30 mg/min, release duration of 120 min (RIVM 2007b)

Dermal – Acute applied dose
59 µg/kg-bw per event

1 The following assumptions were applied to all scenarios: body weight of 70.9 kg for an adult and an inhalation rate of 16.2 m3/day (Health Canada 1998).
2 Use hair gel scenario for amount on head instead of hair conditioner, but use frequency from hair conditioner scenario.
3 The predicted concentration in outdoor air was not estimated, as ConsExpo does not have a model to calculate outdoor inhalation exposures to consumer products. Weather conditions, which can be highly variable and affect ventilation rate as well as temperature, and an undefined room volume (infinitely large) prevent the quantification of reasonable outdoor inhalation exposures (RIVM 2007a).

Appendix 2. Summary of health effects information for 2-methoxypropanol

Endpoint

Lowest effect levels1/Results

Laboratory animals and in vitro

Acute toxicity

Lowest oral LD50 > 5000 mg/kg-bw in rats (BASF 1979a)
[no additional studies identified]

Lowest inhalation LC50 (4 h) > 1600 ppm, equivalent to 5992 mg/m3 in rats (BASF 1979b)
[no additional studies identified]

No dermal acute studies identified.

Short-term repeated-dose toxicity

 

Lowest oral LO(A)EL = 1800 mg/kg-bw per day (the only dose tested) in rats (5 male Wistar rats/group, gavage for 10 days); marginal decreases in erythrocyte counts and the total hemoglobin concentration were observed, no statistical analysis information available (BASF 1982; Ma-Hock et al. 2005)
[no additional studies identified]

Lowest inhalation LO(A)EC = 545 ppm, equivalent to 2040 mg/m3, in rabbits (10–11 pregnant rabbits/group, exposed 6 h/day, through gestation days 6–18), based on maternal toxicity evidenced by significantly reduced body weights and increased placental weights (for developmental effects, see below). Although significantly decreased uterus weights were observed at 225 and 350 ppm, the authors speculated that it was at least partially related to the low number and weights of fetuses; NOEC = 145 ppm, equivalent to 543 mg/m3 for maternal and developmental effects (BASF 1988b; Hellwig et al. 1994).
[no additional data identified]

No dermal studies identified.

Subchronic toxicity

No data identified.

Chronic toxicity/ carcinogenicity

No data identified.

Genotoxicity and related endpoints: in vivo

No data identified.

Genotoxicity and related endpoints: in vitro

Gene mutation
Negative results:
Ames tests in Salmonella typhimurium TA98, TA100, TA1535, TA1537, TA1538, with and without activation (BASF 1988a)

Developmental toxicity

Lowest inhalation LO(A)EC = 225 ppm (843 mg/m3) in rabbits (10–11 pregnant rabbits/group, exposed 6 h/day, through gestation days 6–18), based on significantly increased soft tissue and skeletal variations, such as dilated renal pelvis, hydroureter, separated origin of carotids, truncus arteriosus communis, absent phalanges, absent or poorly developed metatarsal bones, fused ribs and sternebrae, and enlarged rib cartilage. Malformations occurred in a dose‑related manner at higher concentrations. At 545 ppm (2040 mg/m3), all fetuses showed malformations. NOEC = 145 ppm (543 mg/m3) (BASF 1988b; Hellwig et al. 1994).
[additional studies: BASF 1986]

No oral or dermal studies identified.

No data identified.

Sensitization

No data available.

Irritation

Skin irritation
Negative to rabbit skin (BASF 1979a)

Eye irritation
Negative to rabbit eye (BASF 1979a)

1 LC50, median lethal concentration; LD50, median lethal dose; LO(A)EC, lowest-observed-(adverse-)effect concentration; LO(A)EL, lowest-observed-(adverse-)effect level; NO(A)EC, no-observed-(adverse-)effect concentration.

Footnotes

1 For comparison purposes, two scenarios were used to estimate dermal exposure from this product (solvent-rich paint scenario and general coating scenario).