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ARCHIVED - Environmental Screening Assessment Report on Polybrominated Diphenyl Ethers (PBDEs) - Draft for Public Comments

Fate, Exposure and Effects

With their low vapour pressures, very low water solubility and high log octanol/water partition coefficient (Kow) values (Table 2), it is expected that PBDEs entering the environment will tend to bind to the organic fraction of particulate matter. For instance, if it is assumed that equal quantities of pentaBDE are released to air, water and soil compartments, Level III fugacity modelling (EPI v. 3.10, Syracuse Research Corporation) indicates that much of the substance would be expected to partition to sediment (approximately 59%), followed by soils (approximately 40%), water (1.2%) and air (0.2%). Partitioning characteristics for the other PBDEs subject to this assessment are very similar.

The lower brominated PBDEs (tetra- to heptaBDEs) are slightly more soluble in water and have a greater propensity for volatilization and atmospheric transport than highly brominated PBDEs. In the atmosphere, these homologues would also tend to partition to particulates. The higher brominated PBDEs are reported to have higher LogKow and Logaw values and a greater propensity to remain in a solid form, and thus, any transport would likely be in a particle form. Researchers have noted that the transport of the lower brominated PBDEs may be characterized by a series of deposition/revolatilization hops which are dependent on seasonally and diurnally fluctuating temperatures (Gouin and Harner 2003).

Wania and Dugani (2003) examined the long range transport potential of PBDEs with various models (i.e., TaPL3-2.10, ELPOS-1.1.1, Chemrange-2 and Globo-POP-1.1) using various physical and chemical properties (i.e., solubility in water, vapour pressure, logKow, logKoa, logKaw and estimated half-lives in different media). They found that all models yielded comparable results with tetraBDE showing the greatest atmospheric transport potential and decaBDE the lowest transport potential. They estimated a characteristic travel distance (CTD) ranging from 1,113 to 2,483 km for tetraBDE, 608 to 1,349 km for pentaBDEs, and 480 to 735 km for decaBDE. The CTD is the distance a parcel of air has traveled until 1/e or 63% of the chemical has been removed by degradation or deposition processes (Gouin and Mackay 2002).

In an earlier study, Dugani and Wania (2002) also predicted using models that of the various PBDE congeners, those with four to six bromine atoms would have a higher long-range transport potential than lower or higher brominated congeners. They found that the transport of lower brominated congeners is limited by their degradation in the atmosphere, while the transport of the more highly brominated congeners is limited by their low volatility. Atmospheric degradation is reduced at low temperatures, so some of the models may underestimate the long range transport potential of the lighter congeners (Dugani and Wania 2002).

As will be indicated later in this report, PBDE concentrations have increased exponentially in arctic biota over the past two decades and have been measured in arctic air. This suggests efficient long-range atmospheric transport of PBDEs.

Table 2: Selected Physical and Chemical Properties of Commercial PBDEs and their Constituents
Molecular weight485.8 (tetraBDE)
564.7 (pentaBDE)
(WHO 1994)
643,6 (hexaBDE)
722,3 (heptaBDE)
801,4 (octaBDE)
(WHO, 1994)
880,4 (nonaBDE)
959,2 (decaBDE)
(WHO, 1994)
Physical state (20°C; 101.325 kPa)viscous liquid or semi-solid, white crystalline solid (pure isomers of pentaBDE)(European Communities 2000)powder or flaked material(European Communities 2002b)crystalline powder(European Communities 2002a)
Vapour pressure (21°C; Pa)4,69 × 10-5
(Stensel et Nixon 1997 in European Communities, 2000)
6,59 × 10-6
(CMABFRIP, 1997a, 1.58 x 10-6 - 4.68 x 10-7 (hexa-heptaBDEs 25 oC ; Tittlemier et al. 2002)
4,63 × 10-6
(CMABFRIP, 1997e), 2.95 x 10-9 (estimated for decaBDE ; Wania et Dugani 2003)
Water solubility (25°C; µg/L)13,3
10,9 (tetraBDE)
2,4 (pentaBDE)
(Stenzel et Markley, 1997)
(CMABFRIP, 1997b)
(CMABFRIP, 1997f)
Log Koe6,57 (MacGregor et Nixon, 1997)6,29
(CMABFRIP, 1997c)
(Watanabe et Tatsukawa 1990 in European Communities, 2002b)
(CMABFRIP, 1997g)
(Watanabe et Tatsukawa 1990 in European Communities, 2002a)
Constante de la loi d'Henry (25 °C; Pa·m3/mol)11 (European Communities, 2000)10,6 (estimation) European Communities, 2002b)>44 (estimation) European Communities, 2002a)

PBDEs have been detected in all environmental media (see Tables 3 and 4), and there is evidence that their levels in the North American environment are increasing. Gouin et al. (2002) measured total PBDEs (sum of 21 congeners) ranging from 10 to 1300 pg/m3 in air samples collected at a rural southern Ontario site in early spring of 2000. Total PBDEs (congeners not specified) up to 28 pg/m3 were detected in air samples from the Canadian Arctic collected over the period 1994-1995 (Alaee et al. 2000).

Luckey et al. (2002) measured total (dissolved and particulate phases) PBDE (mono- to heptaBDE congeners) concentrations of approximately 6 pg/L in Lake Ontario surface waters in 1999. More than 60% of the total was composed of BDE47 (tetraBDE) and BDE99 (pentaBDE), with BDE100 (pentaBDE) and BDEs 153 and 154 (heptaBDE congeners) each contributing approximately 5 to 8% of the total. Stapleton and Baker (2001) analyzed water samples from Lake Michigan in 1997, 1998 and 1999 and found that total PBDE concentrations (BDEs 47, 99, 100, 153, 154 and 183) ranged from 31 to 158 pg/L.

PBDEs have been detected in sediment and soil samples collected throughout North America, and high concentrations have been measured in sewage sludge. Rayne et al. (2003) measured PBDE concentrations (sum of 8 di- to pentaBDE congeners) ranging from 2.7 to 91 µg/kg OC in 11 surficial sediments collected in 2001 from several sites along the Columbia River system in southeastern British Columbia. Domestic wastewaters arising from septic field inputs were identified as potentially dominant sources of PBDEs in the region. Dodder et al. (2002) reported concentrations of total tetra, penta- and hexaBDE ranging from approximately 5 to 38 µg/kg dw in sediment from a lake in the U.S. located near suspected PBDE sources. Preliminary results from a study by Muir et al. (2003) describe concentrations of BDE209 along a north-south transect from southern Ontario/upper New York state to Ellesmere Island. The highest concentrations of BDE209 (up to12 µg/kg dw) occurred in sediments collected from the western basin of Lake Ontario. However, sediments from two Arctic lakes also had measurable concentrations of 0.075 and 0.042 µg BDE209/kg dw. One of the two Arctic lakes was located near an airport and so inputs of PBDEs from this source could not be ruled out. However, the second lake was completely isolated and was only visited for sampling purposes. The authors speculate that BDE209 was likely transported on particles to the Canadian Arctic due to its low vapour pressure and high octanol-water partition coefficient. Hale et al. (2002, 2003) reported concentrations of total PBDEs (tetra- and pentaBDE) of 76 µg/kg dw in soil near a polyurethane foam manufacturing facility in the United States, and 13.6 µg/kg dw in soil downwind from the facility.

La Guardia et al. (2001) analyzed 11 sludge samples before land application from a sewage treatment facility in the Toronto area and from10 facilities throughout the continental United States. Total PBDEs (sum of 11 tetra- to decaBDE congeners) in the sample of sewage sludge were 8280 µg/kg dw at the Toronto site, while those in the U.S. ranged from 730 to 24, 900 µg/kg dw. Kolic et al. (2003) investigated PBDE levels in sewage sludge from 12 sites in southern Ontario and found concentrations of total PBDEs (21 mono- to decaBDE congeners) ranging from 1414 to 5545 µg/kg dw. Hale et al. (2002) measured total PBDEs (sum of BDEs 47, 99, 100 and 209) of 3005 µg/kg dw in sludge sample collected in 2000 from a regional sewage treatment plant discharging to the Dan River in Virginia.

Alaee et al. (1999) reported average concentrations in the blubber of marine mammals from the Canadian Arctic as 25.8 µg/kg lipid in female ringed seals (Phoca hispida), 50.0 µg/kg in the blubber of male ringed seals, 81.2 µg/kg lipid in female beluga (Delphinapterus leucus) and 160 µg/kg lipid in male beluga. In these samples, congeners of tetraBDE and pentaBDE were predominant. Ikonomou et al. (2000) reported PBDE concentrations in biota samples from the west coast and Northwest Territories of Canada. The highest concentration of total PBDE residues, 2269 µg/kg lipid, was found in the blubber of a harbour porpoise from the Vancouver area. With a concentration of about 1200 µg/kg lipid, a tetraBDE congener accounted for slightly more than half of the total PBDE in the sample. Ikonomou et al. (2002a,b) analyzed temporal trends in Arctic marine mammals by measuring PBDE levels in the blubber of Arctic male ringed seals over the period 1981-2000. Mean total PBDE concentrations increased exponentially from approximately 0.6 µg/kg lipid in 1981 to 6.0 µg/kg lipid in 2000, a greater than 8-fold increase. tetraBDE was again predominant, followed by pentaBDE. A marked increase in tissue PBDE levels was also evident in blubber samples collected from San Francisco Bay harbour seals over the period 1989-1998 (She et al. 2002).

Concentrations of total PBDEs (tetra-, penta- and hexaBDE) rose from 88 µg/kg lipid in 1989 to a maximum of 8325 µg/kg lipid in 1998, a period of only 10 years. Stern and Ikonomou (2000) examined PBDE levels in the blubber of male southeast Baffin beluga whales over the period 1982-1997 and found that the levels of total PBDEs (tri- to hexaBDE) increased significantly. Mean total PBDE concentrations were about 2 µg/kg lipid in 1982 and reached a maximum value of about 15 µg/kg lipid in 1997. Total PBDE residues in the blubber of St. Lawrence estuary belugas sampled in 1997-1999 amounted to 466 (± 230) µg/kg wet weight (ww) blubber in adult males and 665 (± 457) µg/kg ww blubber in adult females. These values were approximately 20 times higher than concentrations in beluga samples collected in 1988-1990 (Lebeuf et al. 2001).

Table 3: Measured Concentrations of PBDEs in the North American Ambient Environment and Sewage Sludge
MediumLocation; YearTotal PBDEsReference
AirAlert, Canada; 1994-19951-28 pg/m3Alaee et al. 2000
AirGreat Lakes; 1997-19995.5-52 pg/m3Strandberg et al. 2001
AirSouthern Ontario; 200010-1300 pg/m3Gouin et al. 2002
AirOntario; 20003.4-46 pg/m3Harner et al. 2002
WaterLake Michigan; 1997-199931-158 pg/LStapleton and Baker 2001
WaterLake Ontario; 19996 pg/LLuckey et al. 2002
SedimentLake Michigan; 19984.2 µg/kg dwStapleton and Baker 2001
SedimentBritish Columbia; 20012.7-91 µg/kg OCRayne et al. 2003
SoilUnited States; 2000<0.1-76 µg/kg dwHale et al. 2002
Sewage SludgeToronto, Canada
United States
8280 µg/kg dw
730-24 900 µg/kg dw
La Guardia et al. 2001
Sewage SludgeUnited States; 20003005 µg/kg dwHale et al. 2002


Table 4: Measured Concentrations of PBDEs in North American Biota
OrganismLocation; yearTotal PBDEsReference
Dungeness crab hepatopancreasWest coast, Canada; 1993-19954.2-480 µg/kg lipidIkonomou et al., 2002b
Mountain whitefish (muscle)Columbia River, British Columbia; 1992-20000.726-131 µg/kg wwRayne et al., 2003
Heron eggBritish Columbia; 1983-20001.308-288 µg/kg wwWakeford et al., 2002
Murre eggNorthern Canada; 1975-19980.442-2.93 µg/kg wwWakeford et al., 2002
Fulmar eggfNorthern Canada; 1975-19980.212-2.37 µg/kg wwWakeford et al., 2002
Beluga whale blubberCanadian Arctic81.2-160 µg/kg lipidAlaee et al., 1999
Herring gull eggGreat Lakes; 1981-20009.4-1544 µg/kg wwNorstrom et al., 2002
Lake troutLake Ontario; 1997
Lake Erie; 1997
Lake Superior; 1997
Lake Huron; 1997
95 µg/kg ph
27 µg/kg ph
56 µg/kg ph
50 µg/kg ph
Luross et al., 2002
Rainbow troutSpokane River, Washington, USA; 1999297 µg/kg wwJohnson et Olson, 2001
Mountain whitefishSpokane River, Washington, USA; 19991 250 µg/kg wwJohnson et Olson, 2001
Largescale suckerSpokane River, Washington, USA; 1999105 µg/kg wwJohnson et Olson, 2001
CarpVirginia, USA; 1998-19991 140 µg/kg wwHale et al. 2001

These studies indicate that PBDE levels in Canadian biota are rising, with dramatic increases in tissue concentrations evident over the last two decades. The highest levels in biota are associated with industrialized regions; however, the increasing incidence of PBDEs in Arctic biota provides increasing evidence for long-range atmospheric transport of these compounds (Stern and Ikonomou 2000). Although the tetraBDE predominates in wildlife, there are recent indications of a shift in tissue congener profiles. Ikonomou et al. (2002a) determined that over the period 1981-2000, penta- and hexaBDE levels in the blubber of Arctic ringed seals increased at rates that were roughly equivalent and about twice that of tetraBDE.

Based on a time trend analysis of PBDE levels in Arctic ringed seals, Ikonomou et al. (2002a) asserted that if present rates of bioaccumulation continue unchanged, PBDEs will surpass polychlorinated biphenyls (PCBs) as the most prevalent organohalogen compound in Arctic seals by 2050. By contrast, there are indications from recent studies conducted in Europe that PBDE levels in some European biota may have peaked. Time trend analyses using Baltic guillemot (Uria aalge) eggs (Sellström 1996; Sellström et al. 2003) and pike (Esox lucius) from Lake Bolmen in Sweden (Kierkegaard et al. 1999b, Submitted in text) show a levelling off and possible decline in the concentrations of penta-like congeners beginning in the early 1990s. Any observed reduction in the concentrations of PBDEs in European biota may be a consequence of recent reductions in the production and use of commercial PeBDE throughout Europe. These results provide evidence that the PBDE contamination evident in North American biota is predominantly North American in origin and not derived from European sources (Ikonomou et al. 2002a). For further discussion of this issue, the reader should consult references such as de Wit (2002) and Law et al. (2003).

An analysis of archived herring gull eggs (sampled in 1981, 1983, 1987, 1988, 1989, 1990, 1992, 1993, 1996, 1998, 1999 and 2000) enabled Norstrom et al. (2002) to establish temporal trends in PBDE concentrations between 1981- 2000. At Lake Michigan, Lake Huron and Lake Ontario sites, concentrations of total tetra- and pentaBDEs increased 71 to 112 fold over the 1981 to 2000 period (from 4.7 to 400.5 µg/kg ww at Lake Ontario; from 8.3 to 927.3 µg/kg ww at Lake Michigan; from 7.6 to 541.5 µg/kg ww at Lake Huron). These increases were all found to be exponential at all three locations. Overall, the total PBDEs ranged from a low of 9.4 µg/kg ww in Lake Ontario to a high of 1544 µg/kg ww Lake Michigan in 1998. These increases were largely due to the tetra- and pentaBDE congeners, but hexa- and heptaBDEs also increased during this period.

Empirical and predicted data indicate that all PBDEs subject to this environmental screening assessment are highly persistent, and each satisfies the requirements for persistence as defined by the Persistence and Bioaccumulation Regulations under CEPA 1999 (see Table 5). Specifically, tetra-, penta-, hexa- and heptaBDEs have been measured in the Arctic environment in spite of their very low vapour pressures, providing evidence that they are subject to long-range atmospheric transport. decaBDE in natural sediments has been shown to be stable and resistant to biodegradation under anaerobic conditions for up to 2 years (de Wit 2000). A preliminary study has also detected decaBDE in Arctic sediments (Muir et al. 2003). In this study, three Arctic lakes were sampled in Nunavut in the Canadian Arctic. Romulus Lake had non-detectable levels (detection limit 0.1 µg/kg dry weight [dw]) of PBDEs in its sediment core. Lake AX-AJ and Char Lake had concentrations of 0.075 and 0.042 µg/kg dw, respectively (detection limit not specified). The authors speculated that decaBDE was likely transported on particles to the Canadian Arctic due to its low vapour pressure and high octanol-water partition coefficient.

Table 5: Persistence and Bioaccumulation Criteria as Defined in CEPA 1999 Persistence and Bioaccumulation Regulations (Environment Canada 2000)
Air>= 2 days or is subject to atmospheric transport from its source to a remote areaBAF >= 5000
Water>= 182 days (>= 6 months)BCF >= 5000
Sediment>= 365 days (>= 12 months)log Kow >=5
Soil>= 182 days (>= 6 months) 

a A substance is persistent when at least one criterion is met in any one medium.
b When the bioaccumulation factor (BAF) of a substance cannot be determined in accordance with generally recognized methods, then the bioconcentration factor (BCF) of a substance will be considered; however, if neither its BAF nor its BCF can be determined with recognized methods, then the log Kow will be considered.

Although all PBDEs subject to this assessment are considered to be persistent, evidence shows that PBDEs are susceptible to some degree of degradation. Studies have shown the transformation of higher brominated PBDEs (e.g., hepta- to decaBDEs) to lower brominated congeners (e.g., tetra- to hexaBDEs), which are associated with high levels of bioaccumulation. A dietary exposure study has shown that congeners of heptaBDE and pentaBDE rapidly biotransform in the gut of carp (Cyprinus carpio), and at least 10-12% is debrominated to congeners of hexaBDE and tetraBDE, respectively (Stapleton 2003; Stapleton and Baker 2003). These transformation products then accumulate in the tissues of the carp. Carp have also demonstrated a limited ability to biotransform decaBDE when exposed via food, producing various penta- to octaBDE congeners. In a study described by Stapleton (2003) and Stapleton and Baker (2003), less than 1% of consumed decaBDE was shown to biotransform in carp to form penta- to octaBDEs.

Many studies have also shown that PBDEs found in PeBDE, OBDE and DBDE are susceptible to photodegradation under varied laboratory conditions (e.g., Norris et al. 1973, 1974; Herrmann et al. 2003; Hua et al. 2003; Peterman et al. 2003). For instance, decaBDE in toluene exposed to artificial sunlight has been found to have a half-life of less than 15 minutes. When dispersed in solvent and then applied to substrates, such as soils and sediments, the half-life of decaBDE is slower (up to approximately 200 hours) (Sellström et al. 1998; Tysklind et al. 2001; Söderström et al. 2003). Their persistence in the atmosphere and susceptibility to long range atmospheric transport is supported by the finding showing that PBDEs have slower rates of photodegradation when associated with particulates.

While highly brominated PBDEs have not been observed to biodegrade under anaerobic or aerobic conditions, even when studied for periods of up to 2 years, there is speculation that biodegradation of highly brominated PBDE congeners may occur over the long term under anaerobic conditions, based on reductive dehalogenation observed with polybrominated biphenyls (PBBs) and PCBs (European Communities 2002a).

Globally, DBDE has become the most used technical PBDE product (see Table 1). There is a weight of evidence suggesting that highly brominated PBDEs such as octa- and decaBDE are precursors of the more toxic, bioaccumulative and persistent lower brominated PBDEs. While the degree to which this phenomenon adds to the overall risk presented to organisms from formation of the more toxic and persistent tetra- to hexaBDE congeners is not known, there is sufficient evidence to warrant concern.

Measured data indicate that tetra-, penta- and hexaBDE are highly bioaccumulative, with bioconcentration factors (BCFs) exceeding 5000 for aquatic species; thus, they satisfy the criteria for bioaccumulation as described in the CEPA 1999 Persistence and Bioaccumulation Regulations (see Table 5). A BCF of about 27 400 L/kg for PeBDE was reported by European Communities (2000), based on a recalculation of data contained in a study by CITI (1982), in which carp were exposed for 8 weeks to PeBDE at 10 or 100 µg/L. This BCF for the commercial product was driven by a high BCF calculated for the tetraBDE component. The recalculated BCFs for the various components were 66 700 L/kg for tetraBDE, 17 700 and 1440 L/kg for separate pentaBDE congeners (identities not provided) and 5640 and 2580 L/kg for separate hexaBDE congeners (identities not provided). A bioaccumulation factor (BAF) of 1.4 × 106 was reported for PeBDE in blue mussels (Mytilus edulis) exposed for 44 days (Gustafsson et al. 1999). The same study reported BCFs of 1.3 × 106 for tetraBDE and 2.2 × 105 for hexaBDE in these organisms. High rates of accumulation in biota are supported by high log Kow values for PBDEs and reports of biomagnification of tetraBDE and pentaBDE in aquatic food chains (e.g., Alaee and Wenning 2002; de Wit 2002).

Key studies of toxicity to organisms in different environmental media are presented in Table 6. Since testing is frequently carried out using commercial mixtures, effects must frequently be best considered in relation to the total exposures to all congeners involved (see below).

The approach taken in this environmental screening assessment was to examine various supporting information and develop conclusions based on a weight of evidence approach as required under Section 76.1 of CEPA 1999. Particular consideration was given to risk quotient analyses and persistence, bioaccumulation, chemical transformation and trends in environmental concentrations.

This assessment has used data corresponding to commercial products, individual congeners and homologues/isomer groups. The presentation of data and the risk quotient analyses have been structured around the PBDE commercial products since a great deal of empirical data which are central to this assessment (e.g., relevant to environmental toxicity) have been determined using the commercial products. Nonetheless, the risk analysis and scientific evidence presented in this report relate to all congeners found in the commercial products, PeBDE, OBDE and DBDE.

The risk determined for each commercial product is a result of the combined activity of the various co-occurring PBDEs, adding complexity to the interpretation of the results. Due to these reasons, their common chemical structure, and due to issues relating to their chemical transformation, PeBDE, OBDE, DBDE and their brominated constituents are assessed as a group.

Risk quotient analyses, integrating known or potential exposures with known or potential adverse environmental effects, were performed for each of the commercial PBDE products subject to this assessment. An analysis of exposure pathways and subsequent identification of sensitive receptors were used to select environmental assessment endpoints (e.g., adverse reproductive effects on sensitive fish species in a community). For each endpoint, a conservative Estimated Exposure Value (EEV) was selected based on empirical data from monitoring studies. Where monitoring data were not available, the EEVs were based on simple calculation procedures taking into account some degree of local environmental conditions, but largely relying on generic environmental parameters. Chemical concentrations from the Canadian and North American environment were used preferentially for EEVs; however, data from other regions in the world were used in the absence of sufficient Canadian data of satisfactory quality or to provide a weight of evidence. EEVs usually represented worse-case scenarios, as an indication of the potential for these substances to reach concentrations of concern and to identify areas where those concerns would be most likely.

An Estimated No-Effects Value (ENEV) was also determined by dividing a Critical Toxicity Value (CTV) by an application factor. CTVs typically represented the lowest ecotoxicity value from an available and acceptable data set. Preference was generally for chronic toxicity data, as long-term exposure was a concern. Where these data were not available, the following were used in order of preference: acute data, analogue data, quantitative structure-activity relationship (QSAR) data and data derived from equilibrium partitioning methods.

Application factors were derived using a multiplicative approach, which uses 10-fold factors to account for various sources of uncertainty associated with making extrapolations and inferences related to the following: intra- and interspecies variations; differently sensitive biological endpoints; laboratory-to-field impact extrapolation required to extrapolate from single-species tests to ecosystems; and potential effects from concurrent presence of other substances. For substances that meet both the persistence and bioaccumulation criteria as outlined in the CEPA 1999 Regulations (see Table 5), an additional application factor of 10 is applied to the CTV.

Risk quotients derived for PBDEs are summarized in Table 7. Exposure data used as EEVs can be found in Tables 3 and 4 or are summarized in the notes to Table 7. Toxicity data used to determine CTVs and ENEVs are summarized in Table 6.

The risk quotient analysis indicates that the greatest potential for risk from PBDEs in the Canadian environment is due to the secondary poisoning of wildlife from the consumption of prey containing elevated PeBDE and OBDE congener concentrations. Elevated concentrations of components of PeBDE in sediments may present risk to benthic organisms. hexaBDE is a component of both PeBDE and OBDE and could be a product of heptaBDE, octaBDE, nonaBDE or decaBDE transformation. Therefore, risk associated with components of PeBDE may be due to the use of OBDE or debromination of highly brominated PBDEs, in addition to the use of PeBDE itself. The risk analysis for soil organisms indicates that risk quotients were below 1 for PeBDE, OBDE and DBDE; however, the lack of data characterizing PBDE concentrations in soil and sewage sludge applied to soil indicates the need for further research. PeBDE, OBDE and DBDE would present low potential for risk as a result of direct toxicity to pelagic organisms due to their very low water solubility. In the water column, risk associated with components of PeBDE and OBDE (tetra-, penta- and hexaBDE congeners) may be due to bioaccumulation and toxicity to secondary consumers.

There is a lack of data characterizing the toxicity of PBDEs to wildlife. Recent studies using rodents provide evidence that exposure to PBDEs may lead to behavioural disturbances, disruptions in normal thyroid hormone activity and liver effects (e.g., Eriksson et al. 2002, Zhou et al. 2001 and 2002, Great Lakes Chemical Corporation 1984). The relationship of these studies to potential effects from accumulation in the wild requires further study.

There are a variety of data indicating that all PBDE congeners subject to this assessment are highly persistent and each satisfies the requirements for persistence as defined by CEPA 1999 Persistence and Bioaccumulation Regulations.

Although all PBDEs subject to this assessment are considered to be persistent, evidence shows that PBDEs are susceptible to some degree of degradation. Studies have shown the transformation of higher brominated PBDEs (e.g., hepta- to decaBDEs) to lower brominated congeners (e.g., tetra- to hexaBDEs) which are associated with high levels of bioaccumulation.

DBDE has become the prevalent commercial PBDE product used in North America and the world. In North America and Europe, it is often found in concentrations which exceed those of other PBDEs in sewage sludge and sediments. Concentrations of DBDE are now reaching mg/kg dw levels in North American sewage sludge. High accumulation of DBDE in the environment and evidence of debromination has led researchers to note that even slight and very long term degradation to lower brominated diphenyl ethers could have serious ecological consequences over periods spanning several decades. Thus, while current concentrations measured in the environment for homologues found in commercial DBDE do not appear to exceed known effect thresholds, their overall persistence and potential transformation to bioaccumulative forms, and observed commercial and environmental trends, indicate environmental concerns.

Measured data indicate that tetra-, penta- and hexaBDE are highly bioaccumulative and satisfy the criteria for bioaccumulation in the CEPA 1999 regulations. Concentrations of PBDEs in herring gull eggs have increased exponentially between 1981 and 2000 at Lake Ontario, Huron and Michigan sampling sites. Concentrations of PBDEs (predominantly tetra- and pentaBDE congeners) have also increased exponentially between 1981 and 2000 in Arctic male ringed seals. There is a weight of evidence showing that highly brominated PBDEs are precursors of bioaccumulative and persistent PBDEs. While it is not known the degree to which this phenomenon adds to the overall risk presented to organisms from the tetra- to hexaBDE congeners, there is sufficient evidence for concern. The Government of Canada Toxic Substances Management Policy (TSMP) notes that “where a Track 1 substance results from the degradation or transformation of a parent substance in the environment, the parent substance may also be considered for Track 1.”

Pyrolysis and extreme heating can cause all PBDEs to form brominated dibenzo-p-dioxins and dibenzofurans (European Communities 2000, 2002a,b). These transformation products are considered brominated analogues of the TSMP Track 1 polychlorinated dibenzo-p-dioxins and dibenzofurans.

The PBDEs subject to this assessment have low vapour pressures and low Henry’s Law constants (see Table 2) and are not expected to partition significantly into the atmosphere. As such, they are considered to present a negligible risk with respect to atmospheric processes such as global warming, stratospheric ozone depletion and ground-level ozone formation; however, they do reside in the atmosphere adsorbed to suspended particulates and can be transported over long distances.

It is therefore concluded that tetraBDE, pentaBDE, hexaBDE, heptaBDE, octaBDE, nonaBDE and decaBDE, which are found in commercial PeBDE, OBDE and DBDE, are 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 and thus satisfy the definition of “toxic” under Paragraph 64(a) of CEPA 1999. Based on considerations of potential contribution to atmospheric processes, it is concluded that PBDEs are not entering the environment in a quantity or concentrations or under conditions that constitute or may constitute a danger to the environment on which life depends, and thus do not satisfy the definition of “toxic” under Paragraph 64(b) of CEPA 1999.

The available data regarding persistence and bioaccumulation of tetraBDE, pentaBDE, hexaBDE indicated that they satisfy the criteria outlined in the Persistence and Bioaccumulation Regulations of CEPA 1999. Their presence in the environment results primarily from human activity, and they are not naturally occurring radionuclides or naturally occurring inorganic substances. Data regarding the potential debromination of higher brominated forms of PBDEs to bioaccumulative forms indicate that they may also be considered as Track 1 substances under the Toxic Substances Management Policy.

Proposed recommendation to the Ministers of the Environment and Health

It is proposed that PBDEs, including tetraBDE, pentaBDE, hexaBDE, heptaBDE, octaBDE, nonaBDE and decaBDE, which are found in commercial PeBDE, OBDE and DBDE, be considered “toxic” as defined in section 64 of CEPA 1999.

It is proposed that consideration be given to adding tetraBDE, pentaBDE, and hexaBDE, which are found in commercial PeBDE and OBDE, to the Virtual Elimination List under CEPA 1999 and that PBDEs, including tetraBDE, pentaBDE, hexaBDE, heptaBDE, octaBDE, nonaBDE and decaBDE, which are found in commercial PeBDE, OBDE and DBDE, be considered as Track 1 substances under the Toxic Substances Management Policy.

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