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Appendix 10Worst-case Scenario Cancer Risk Estimation By Rory B. Conolly at the Chemical Industry Institute of Toxicology (CIIT) March 2005 Estimates of additional lifetime cancer (respiratory tract) were calculated based on worst- case childhood exposures. The details of the CIIT cancer risk model (Conolly et al., 2004) is summarised in Appendix 9. Exposure informationExposure durations Schooling age: 5-17 years old (12 years education) Overall time spent indoors for all age groups: 20 hours per day (based on recent Australian survey data, enHealth Council, 2003) Average duration in schools: 6 hours a day, 5 days a week Indoor air formaldehyde levels The indoor air levels of formaldehyde are based on limited Australian monitoring data, as discussed in Section 13.2, and summarised in Table A10-1. Table A10-1: Indoor air levels of formaldehyde in mobile homes and relocatable buildings Type of building Indoor air level (average) Mobile homes 29 ppb (2000 data) 346 ppb (1991 data) Relocatable buildings No data in classrooms available No recent data in relocatable buildings 710 ppb (1992 data for relocatable offices) Although no data are available for relocatable classrooms, it is reasonable to assume a similar level as relocatable offices.
Scenario A: Based on recent data - 29 ppb for 14 h/day at home and 710 ppb for 6 h/day at school Scenario B: Based on earlier data - 346 ppb for 14 h/day at home and 710 ppb for 6 h/day at school (worst-case) Indoor air exposures for 18-80 year olds were the same for both scenarios (i.e. 30 ppb for 20 hours/day). Ambient formaldehyde levels Ambient air level of formaldehyde is estimated annual average of 5.5 ppb (Section 13.1). Risk estimations and resultsThe cancer risk model used (Conolly et al., 2004) specifies how breathing rate changes on an hour-by-hour basis each day and these changes are incorporated into the analysis of cancer risk, as it affects the respiratory tract dosimetry of formaldehyde. Table A10-2 presents a matrix of formaldehyde levels and ventilation rate used for the risk estimation. Risks were predicted for 80-year lifetimes. The predicted additional risks were 2.9 X 10-7 for scenario A (29 ppb) and 4.5 X 10-7 for scenario B (346 ppb). Most of this risk is attributable in the model to the mutagenic pathway mediated by formation of DNA-protein crosslinks (DPX), with only a small fraction of the predicted risk being attributable to effects on the rate of cell division. This is notable, as the risks were predicted using an upper bound estimate of the value of the parameter (KMU) that links DPX with direct mutation. In the statistical development of the model the best estimate of the value of KMU was zero (0). Figure A10-1 shows the predicted relationships between duration of exposure and additional cancer risk using the upper bound estimate for KMU. 
Figure A10-1: Predicted additional risks for the two exposure scenarios. Table A10-2: Exposure concentrations – respiratory ventilation rate matrixa
aThe 24 h day is partitioned by exposure concentrations and breathing rate. This table can be used to identify concentration – breathing rate pairs for a full 80-year lifetime. b maximum average in Australian conventional homes (Section 13.2). 266 Priority Existing Chemical Assessment Report No. 28 Directory: data -> assets -> word doc -> 0006 word doc -> Commonwealth of Australia 2002 word doc -> Commonwealth of Australia 2000 word doc -> Priority Existing Chemical word doc -> Rail safety news issue 6 – October 2011 word doc -> Review of Multiple Chemical Sensitivity: Identifying 0006 -> Board Endorsed October 2009 amended 13-09-11 with extra units 0006 -> Rt Hon Andrew Lansley cbe mp secretary of State for Health 0006 -> Environmental Approvals Application Form Use this form Download 5.77 Mb. Share with your friends:
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