We have identified two…

We have identified two concerns relating to the toxicity reference values (TRVs) used in the derivation of the “Recommended Health-Based Indoor Air Target Levels for Selected VOCs” (Appendix IV) proposed in the document. The TRVs of concern relate to the chronic inhalation of trichloroethylene and tetrachloroethylene in indoor air. Recent evaluations by reputable regulatory agencies have resulted in the derivation of new chronic-duration inhalation exposure limits protective of non-cancer and carcinogenic effects, which are more conservative those recommended by MOE (2011) for these two chemicals. Further, we have received MOE reviewer comments on O. Reg. 153/04 risk assessments submitted to the MOE indicating that QPRAs should consider using the more up-to-date exposure limits than those recommended by MOE (2011). We are seeking clarification why the MOE has proposed indoor air target levels for trichloroethylene and tetrachloroethylene derived using exposure limits that are no longer the most up-to-date. 1) Discussion regarding the exposure limits used for proposed trichloroethylene indoor air target level a) The chronic inhalation trichloroethylene reference concentration (RfC) of 40 µg/m3 recommended for use in O. Reg. 153/04 risk assessments by MOE (2011) was derived by US EPA NCEA (2001). A more conservative RfC of 2 µg/m3 has since been derived by US EPA IRIS (2011a), based on increased fetal cardiac malformations in rats (Johnson et al., 2003) and decreased thymus weights in mice (Keil et al., 2009). b) The trichloroethylene inhalation unit risk (IUR) of 2.0x10-6 (µg/m3) -1 derived by Cal EPA (2009) was recommended for use by MOE (2011). A more conservative IUR of 4.0x10-6 (µg/m3) -1 has since been derived by US EPA (2011) and US EPA IRIS (2011b) based on increased risks of renal cell carcinoma, non-Hodgkin's lymphoma, and liver cancer risks (Charbotel et al., 2006). In recent risk assessment submissions (O. Reg. 153/04) to the MOE, we have received review comments relating to the use of the TRVs recommended by MOE (2011) for trichloroethylene. These comments indicate that the QPRA should consider using the most up-to-date TRVs, suggesting that the RfC and IUR recommended by MOE (2011) are no longer appropriate for use for the derivation of risks and health-based indoor air trigger concentrations. Further, the critical effect identified by US EPA IRIS (2011a) entails that risk assessors need to consider trichloroethylene as a developmental toxicant via the inhalation route (i.e., no time-weighting or application of adjustment factors for time spent on-site). This approach is not reflected in the indoor air criteria proposed by the MOE. Can the MOE provide insight as to why the proposed health-based indoor air target levels for trichloroethylene do not consider the most up-to-date regulatory exposure limits? 2) Discussion regarding the exposure limits used for proposed tetrachloroethylene indoor air target level a) The chronic inhalation tetrachloroethylene reference concentration (RfC) of 250 µg/m3 recommended for use in O. Reg. 153/04 risk assessments by MOE (2011) was derived by WHO (2000). A more conservative RfC of 40 µg/m3 has since been derived by US EPA IRIS (2012a), based neurotoxicity in occupationally exposed adults (Echeverria et al., 1995; Cavalleri et al., 1994). b) A tetrachloroethylene inhalation unit risk (IUR) was not recommended for use by MOE (2011). An IUR of 2.6x10-7 (µg/m3) -1 was recently derived by US EPA IRIS (2012b) based on increased hepatocelluluar carcinoma in mice (JISA, 1993). In recent risk assessment submissions (O. Reg. 153/04) to the MOE, we have received review comments relating to the use of the TRV recommended by MOE (2011) for tetachloroethylene. These comments indicate that the QPRA should consider using the most up-to-date TRVs, suggesting that the RfC recommended by MOE (2011) is no longer appropriate for use for the derivation of risks and health-based indoor air trigger concentrations. Further, the critical effect identified by US EPA IRIS (2012b) entails that risk assessors need to consider tetrachloroethylene as a carcinogen via the inhalation route. This approach is not reflected in the indoor air criteria proposed by the MOE. Can the MOE provide insight as to why the proposed health-based indoor air target levels for tetrachloroethylene do not consider the most up-to-date regulatory exposure limits? References: Cal EPA. 2009. Air Toxics Hot Spots Program Risk Assessment Guidelines, Part II: Technical Support Document for Describing Available Cancer Potency Factors. California Environmental Protection Agency, Office of Environmental Health Hazard Assessment. Available at http://www.oehha.ca.gov/air/hot_spots/2009/AppendixB.pdf [November 18, 2013]. Cavalleri, A; Gobba, F; Paltrinieri, M; Fantuzzi, G; Righi, E; Aggazzotti, G. (1994). Perchloroethylene exposure can induce colour vision loss. Neurosci Lett 179: 162-166. http://dx.doi.org/10.1016/0304-3940(94)90959-8. Cited in : US EPA IRIS, 2012a. Charbotel, B., Fevotte, J., Hours, M., Martin, J-L., Bergeret, A. 2006. Case-control study on renal cell cancer and occupational exposure to trichloroethylene. Part II: Epidemiological aspects. Ann Occup Hyg50: 777-787. Cited in: US EPA IRIS, 2011b; US EPA, 2011. Echeverria, D., White, R.F., and Sampaio, C. 1995. A behavioral evaluation of PCE exposure in patients and dry cleaners: A possible relationship between clinical and preclinical effects. J Occup Environ Med 37: 667-680. Cited In: US EPA IRIS, 2012a. JISA. 1993. Carcinogenicity study of tetrachloroethylene by inhalation in rats and mice. Japan Industrial Safety Association. Hadano, Japan. Cited In: US EPA IRIS, 2012b. Johnson, P., Goldberg, S., Mays, M., Dawson, B. 2003. Threshold of trichloroethylene contamination in maternal drinking waters affecting fetal heart development in the rat. Environ Health Perspect, 111, 289-292. Cited in: US EPA IRIS, 2011a; US EPA 2011. Keil, D.E., Peden-Adams, M.M., Wallace, S., Ruiz, P., Gilkeson, G.S. 2009. Assessment of trichloroethylene (TCE) exposure in murine strains genetically-prone and non-prone to develop autoimmune disease. J Environ Sci Health A Tox Hazard Subst Environ Eng, 44, 443-453. Cited in: US EPA IRIS, 2011a; US EPA 2011. MOE. 2011. Rationale for the Development of Generic Soil and Groundwater Standards for use at Contaminated Sites in Ontario (Draft). Standards Development Branch, Ontario Ministry of the Environment. April 15, 2011. US EPA. 2011. Toxicological review of Trichloroethylene (CASRN 79-01-6) in support of summary information on the Integrated Risk Information System (IRIS). US Environmental Protection Agency. Available at http://hero.epa.gov/index.cfm?action=reference.details&reference_id=736089. [November 18, 2013]. US EPA IRIS. 2011a. Trichloroethylene (CASRN 79-01-6). Health Hazard Assessments for Noncarcinogenic Effects. Integrated Risk Information System. US Environmental Protection Agency. Available at http://www.epa.gov/iris/subst/0199.htm. [November 18, 2013]. US EPA IRIS. 2011b. Trichloroethylene (CASRN 79-01-6). Carcinogenicity Assessment for Lifetime Exposure. Integrated Risk Information System. US Environmental Protection Agency. Available at http://www.epa.gov/iris/subst/0199.htm. [November 18, 2013]. US EPA IRIS. 2012a. Tetrachloroethylene (Perchloroethylene) (CASRN: 127-18-4). Health Hazard Assessments for Non-Carcinogenic Effects. U.S. Environmental Protection Agency. Integrated Risk Information System. Available at: http://www.epa.gov/iris/subst/0106.htm [November 18, 2013]. US EPA IRIS. 2012b. Tetrachloroethylene (Perchloroethylene) (CASRN: 127-18-4). Carcinogenicity Assessment for Lifetime Exposure. U.S. Environmental Protection Agency. Integrated Risk Information System. Available at: http://www.epa.gov/iris/subst/0106.htm [November 18, 2013]. US EPA NCEA. 2001. Trichloroethylene Health Risk Assessment: Synthesis and Characterization (External Review Draft). US Environmental Protection Agency, Office of Research and Development, National Center for Environmental Assessment, Washington Office, Washington, DC, EPA/600/P-01/002A, 2001. Available at http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=23249. [November 18, 2013]. WHO. 2000. Air Quality Guidelines for Europe. 2nd Edition. World Health Organization. Regional Office for Europe. WHO Regional Publications, European Series, No. 91. ISBN 92 890 1358 3.

[Original Comment ID: 160858]