ESTIMATING RISKS FROM EXPOSURE TO METHYLMERCURY - APPLICATION TO FIRST NATIONS PEOPLE IN CANADA

We combined dose-response analyses with a probabilistic exposure asses sment to estimate the risks to native Canadians who ingest methylmercu ry via fish consumption from natural lakes and a reservoir in British Columbia. Available dose-response data included multivariate measureme nts of central nervous system functioning in Iraqi children exposed to methylmercury prenatally. We applied the method of principal componen ts to simplify the data structure. The first principal component descr ibed close to 80% of the variability in the data, making it a reasonab le choice as an index. The relationship between mercury in maternal ha ir and the probability of an abnormal neurological effects index was m odeled with the logistic and Weibull functions. The goodness-of-fit of the two models is discussed and the results compared to other publish ed dose-response analyses. Exposure distributions were developed to re present methylmercury dose by using observed data on methylmercury con tamination in the lakes and reservoir and reasonable assumptions about other key parameters such as fish consumption. We estimated risks to the target population using Monte Carlo simulation. Consumption of rea sonable quantities of fish from these bodies of water does not pose a significant risk to the aboriginal population.