EXPOSURE PATTERNS AND LONG-TERM SEQUELAE ON ADULTS AND CHILDREN IN 2 CANADIAN INDIGENOUS COMMUNITIES EXPOSED TO METHYLMERCURY

Health Canada has been collecting data on Inuit and First Nations' met hylmercury (MeHg) levels for 25 years. A national overview has been co mpleted and more focussed analyses have now been initiated. This paper deals with two interdependent analytical components: 1) a longitudina l overview of the two most extensively sampled communities in Canada: Grassy Narrows and Whitedog, the residents of which were exposed to 'p oint source' mercury pollution in the 1970's; 2) fetal and post-natal exposure to mercury in these two communities including an outline of t he First Nation MeHg child development pilot project in the two commun ities. A retrospective analysis of Grassy Narrows and Whitedog shows a decreasing MeHg trend in both communities. In Grassy Narrows the aver age individual annual peak methylmercury level in blood has decreased significantly, from 23.80 ppb (range 1.50-322.90) in 1976 to 7.5 ppb ( 1.7-46.7) in 1995 (r=-0.65, p<0.001). In Whitedog the average peak has also decreased significantly, from 12.87 ppb (1.50-172.00) in 1976 to 6.1 ppb (1.7-33.3) in 1995 (r=-0.59, p<0.005). However, behind these positive trends is the reality of two communities still suffering the effects of disrupted lifestyles and socio-cultural damage. A number of cold blood samples, maternal blood samples, and samples from women of child-bearing age from these communities have been in the ''risk'' gr oup (according to the 1990 WHO guidelines). We are therefore now asses sing the long term effects of fetal exposure in the communities. Stand ard clinical examinations in the past failed to prove abnormalities at tributable to methylmercury but did not include subtle neuropsychologi cal development tests. Many of the fetally exposed children are now in secondary school. Therefore, we have initiated a pilot project to ass ess long term effects of methylmercury exposure on the neuropsychologi cal development of these children whose fetal exposure we know. The pi lot child development project which was initiated in 1995 in Grassy Na rrows and Whitedog, with community support, includes four main compone nts: i) a school records review, looking at attendance, marks, and aty pical behaviour; ii) teachers' questionnaires, targeting child behavio ur; iii) an in-depth neuropsychological test battery focussing on subt le factors, such as memory, attention, executive functions, perceptual functions and sensory I motor development; and iv) hair sampling, pro viding current MeHg levels to correlate with results from the previous sampling and findings from the first three components. An overview of progress is given.