A Case Study in Arsenic Risk Assessment: Deloro Village, Ontario. E. Sigal, C. Bacigalupo, R. Moore, G. Ferguson, and S. Fleming, Cantox Environmental Inc., Ontario Ministry of the Environment, Canada
Risk assessment at arsenic contaminated sites is a complex and problematic exercise, the interpretation of which has been a source of controversy and complication when managing these sites. An alternative approach that involves the use of a weight of evidence approach has been successfully used at an arsenic site. The Deloro Village is a community in north-eastern Ontario located near a former gold mine, where nearly a century’s worth of hazardous byproducts and residues have contaminated the area. Sampling indicated that there were elevated levels of arsenic, cobalt and lead in soils in some localized areas of the village. Risk assessment, involving multipathway exposure assessment (air, water, soil, backyard produce, fish and market basket foods) which revealed arsenic risk levels in the 1 in 1000 range (Ontario considers 1 in 1,000,000 to be acceptable). These elevated risk estimates raised community concerns and made communication of the results problematic. Information beyond that typically contained within a risk assessment was needed to complete the decision making process. Further investigation, beyond those typically included in a risk assessment, revealed the following: (i) no statistical difference in levels of arsenic in urine for Deloro and a comparison community; (ii) the levels of arsenic in urine in Deloro were not indicative of any excess levels of illness; (iii) arsenic related cancer incidence in Deloro were not measurably higher than those for elsewhere in Ontario; (iv) predicted exposures and risks for arsenic were only slightly greater than for the typical Ontario resident; and, (v) removal of all soil above background levels would only result in a 2 to 4% overall risk reduction. Consideration of all pieces of evidence (i.e., risk assessment, community health status, urinary arsenic study) led to the conclusion that there were no unsafe exposures or adverse health effects associated with elevated arsenic levels in the Deloro Village.
The Deloro Village Exposure Assessment and Health Risk Characterization study was wholly funded by the Ontario Ministry of the Environment.
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