Tables

Table 1: Substance Identity for HBCD

¹ National Chemical Inventories (NCI). 2009: AICS (Australian Inventory of Chemical Substances); ASIA-PAC (Asia-Pacific
Substances Lists); ECL (Korean Existing Chemicals List); EINECS (European Inventory of Existing Commercial Chemical
Substances); ENCS (Japanese Existing and New Chemical Substances); NZIoC (New Zealand Inventory of Chemicals); PICCS (Philippine Inventory of Chemicals and Chemical Substances); and TSCA (Toxic Substances Control Act Chemical Substance Inventory).
² Simplified Molecular Input Line Entry System

Table 2: Physical and Chemical Properties of HBCD

¹ Estimate was derived using user-entered values for water solubility of 0.0034 mg/L (for the gamma isomer) and vapour pressure of 6.27 × 10^-5 Pa (for the commercial product).
² Estimate was derived using model-entered values for water solubility of 2.089 × 10^-5 mg/L (WSKOWWIN 2000) and vapour pressure of 2.24 × 10^-6 Pa (MPBPWIN 2000).
³ Water solubility is a function of isomer content.

Table 3: Modelled Data for Degradation of HBCD

¹ Expected half-lives for BIOWIN and CPOPs models are determined based on Environment Canada 2009.
² Model does not provide an estimate for this type of structure.

Table 4: Persistence and Bioaccumulation Criteria as Defined in CEPA 1999 Persistence and Bioaccumulation Regulations (Canada 2000)

¹ A substance is persistent when at least one criterion is met in any one medium.
² 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 K_owwill be considered.

Table 5: Modelled Bioaccumulation Data for HBCD

¹ Log K_ow 7.74 (KOWWIN 2000) used
² Log K_ow 5.625 (CMABFRIP 1997a), primarily for γ-isomer, used

Table 6: Concentrations Measured in the Ambient Environment and Waste Treatment Products

¹ Not specified
² Not detected; detection limit not specified
³ Values estimated from graphical representation of data
⁴ Sewage treatment plant
⁵ Wastewater treatment plant
⁶ Dry weight
⁷ Wet weight

Table 7: Concentrations Measured in Biota

¹ Not detected; detection limit not specified
² Not specified

Table 8: Human Milk Lipid Concentrations of Individual HBCD Isomers and Total (Σ) HBCD

Table 9: Human Blood Serum and Cord Plasma for Individual Isomers and ΣHBCD

Table 10: Human Tissue Data for HBCD

Note: In Europe, the calculated margin of safety (MOS) for HBCD was 5.1 x 10⁺³ to 2.0 x 10⁺⁵, exceeding the MOS reference of 5.3 x 10⁺² (Weiss and Bergman 2006b). The 2006 level of HBCD in European humans was not considered to be of concern. It was also determined that the HBCD data were too weak for any assessment in the U.S. at that time.

Table 11: Food Concentrations and Dietary Intakes for ΣHBCD

Note: Roosens et al.’s (2009) dietary estimates of 0-20 ng ΣHBCD/day are lower than those previously reported. They are based on a short snapshot of time of exposure for a small number of individuals; the diets consumed consisted of lean meats and vegetables with low or no HBCD content; there were low detection frequencies of HBCD in the market survey; and LOQ or half LOQ concentrations were used.

Table 12: Dust Concentrations for Individual Isomers and ΣHBCD (Roosens et al. 2009)

Table 13: Mean +/- SD Exposure Factors of α, ß, γ-HBCD in Food, Dust, Serum (Roosens et al. 2009)

Note: Chiral signature of all detected isomers in food and dust was racemic or close to it in all samples above LOQ. The (-)α-HBCD was the dominating enantiomer in human serum. Comparison of exposure factors with other studies is not possible as this is the first study to suggest a racemic chiral signature of HBCD in duplicate diets (Roosens et al. 2009).

Table 14: Measured Total HBCDs Environmental Media Levels

Table 15: European Union Risk Assessment on HBCD

Exposure estimates of the HBCD EU Risk Assessment Report ^1,2 (EU RAR 2008)

¹ The EU RAR concluded that humans are primarily exposed to HBCD mainly by inhalation or ingestion of airborne dust or from direct contact with treated textiles and materials. Inhalation exposure to HBCD vapour is negligible due to HBCD’s low vapour pressure. All these scenarios were found to typically result in insignificant exposures. Indirect exposure via the environment was estimated using EUSES modelling based on measured levels in biota and food. These estimates of exposures were attributed to food basket study data and the ingestion of fish and root crops contaminated with HBCD. Human exposures to HBCD from usage of consumer products or via the environment were concluded to be much lower than occupational exposures. Prenatal and neonatal exposures in utero or via breast feeding were also found to occur.
² The Scientific Committee on Health and Environmental Risks (SCHER) adopted an opinion on the final Human Health Part of the EU Risk Assessment Report (EU RAR) on HBCD. SCHER members felt that the health part of the EU RAR is of good quality, comprehensive and that the exposure and effects assessment adhere to the EU’s Technical Guidance Document.

Table 16: Summary of Key Toxicity Studies Used in the Assessment of HBCD

¹ Study identified that the highest concentration tested did not result in statistically significant results. Since the NOEC could be higher, the NOEC is described as being greater than or equal to the highest concentration tested.
² 500 mg/kg-bw dose could not be dissolved completely in peanut oil carrier, and residue was measured in the stomach cavity of test fish during analysis. Analysis confirmed that the fish had taken up most of the test substance; however, dose was considered to probably be less than 500 mg/kg-bw (i.e., < 500 mg/kg-bw).
³ Not detected
⁴ Value is less than the lowest test concentration used and is therefore considered to be an estimate only.

Table 17: Summary of Data Used in the Risk Quotient Analysis of HBCD

¹ Due to the lack of adequate measured data, PECs were estimated using a fugacity Level III (steady-state) box model described in Appendix B, and in Environment Canada (2009).
² CMABFRIP 1998.
³ An assessment factor of 10 was applied to account for extrapolation from laboratory to field conditions and interspecies and intraspecies variations in sensitivity.
⁴ Oetken et al. 2001.
⁵ The critical toxicity value (CTV) of 29.25 mg/kg dw was obtained using sediments containing 1.8% organic carbon (OC). To allow comparison between the predicted no effects concentration (PNEC) and predicted environmental concentrations ( PECs), the PNEC was standardized to represent sediment with 4% OC.
⁶ Due to the lack of measured soil data, PECs were calculated for tilled agricultural soil and pastureland based on Equation 60 of the European Commission Technical Guidance Document (TGD; European Communities 2003) and the approach by Bonnell Environmental Consulting (2001):
PEC_soil = (C_sludge x AR_sludge) / (D_soil x BD_soil)
where:
PEC_soil = PEC for soil (mg/kg)
C_sludge = concentration in sludge (mg/kg)
AR_sludge = application rate to sludge amended soils (kg/m²/yr); default = 0.5 from Table 11 of TGD
D_soil = depth of soil tillage (m); default = 0.2 m in agricultural soil and 0.1 m in pastureland from Table 11 of TGD
BD_soil = bulk density of soil (kg/m³); default = 1700 kg/m³ from Section 2.3.4 of TGD
The equation assumes no losses from transformation, degradation, volatilization, erosion or leaching to lower soil layers. Additionally, it is assumed there is no input of HBCD from atmospheric deposition and there are no background HBCD accumulations in the soil. To examine potential impacts from long-term application, an application time period of 10 consecutive years was considered. A sludge concentration of 1.401 mg/kg dw reported by Morris et al. (2004) was used as C_sludge in the calculation. As the organic carbon content of the sludge was not specified, a standard OC level of 2% (European Communities 2003) was assumed.
⁷ ACCBFRIP 2003a.
⁸ The CTV of 235 mg/kg dw was obtained using a soil with 4.3% OC. To allow comparison between the PNEC and PECs, the PNEC was standardized to represent a soil with 2% OC.
⁹ Tomy et al. 2004a.
¹⁰ Due to the lack of data for wildlife species, a lowest observed effect level (LOEL) of 100 mg/kg-bw per day, based on significantly reduced levels of circulating thyroid hormones in rats (CMABFRIP 2001), was selected as the CTV for the evaluation of potential effects in wildlife. This endpoint was considered relevant as disruptions in thyroid hormone homeostasis may alter critical metabolic processes such as development of the central nervous system and cell metabolic rates. Interspecies scaling was applied to extrapolate the total daily intake (TDI) in rats to a concentration of food in mink, Mustela vison, a surrogate wildlife species. The calculation used the typical adult body weight (bw; 0.6 kg) and daily food ingestion rate (DFI; 0.143 kg/d ww) of a female mink to estimate a CTV in mink based on exposure through food (CCME 1998). That is, CTV_food = (CTV_{TDI in rats} x bw_mink) / DFI_mink This equation assumes that all of the substance is exposed via food and that the substance is completely bioavailable for uptake by the organism. An allometric scaling factor of 0.94 (Sample and Arenal 1999) was then applied to this CTV value in order to account for observed higher sensitivities in larger animals (i.e., mink) when compared with smaller ones (i.e., rat). The final CTV, incorporating both interspecies and allometric scaling, is therefore 395 mg/kg food ww.
¹¹ An assessment factor of 10 was applied to account for extrapolation from laboratory to field conditions and from a rodent to a wildlife species.