THE EFFECTS OF HEXACHLOROBENZENE ON MINK IN THE CANADIAN ENVIRONMENT - AN ECOLOGICAL RISK ASSESSMENT

Hexachlorobenzene (HCB) is a persistent substance that accumulates in tissues and biomagnifies up the food chain suggesting that biota at hi gher trophic levels (e.g., predatory birds and piscivorous mammals) ar e at the greatest risk of exposure. Although widespread, the highest l evels of HCB in Canada are found in the Great Lakes and connecting cha nnels. Because mink (Mustela vison) are piscivorous mammals known to b e particularly sensitive to the effects of organochlorine substances, we assessed whether mink populations in the Great Lakes area are exper iencing adverse effects as a result of exposure to HCB. A deterministi c, deliberately hyperconservative analysis indicated that recent level s of HCB in air, water, and aquatic organisms are unlikely to pose a s ignificant risk to mink living near Lakes St. Clair, Erie and Superior . The hazard quotients for the St. Clair River area near Sarnia and La ke Ontario, however, indicated potential risks. We conducted Monte Car lo simulations to estimate the probability that mink exposed to HCB in these areas are experiencing reproductive impairment. The results of these analyses indicate: (1) a moderate to high probability that mink in the St. Clair River area are experiencing 5 to 20% declines in repr oductive success due to HCB exposure, and (2) a low probability (<15%) that mink near Lake Ontario are experiencing even modest declines in reproductive fecundity (>5%).