Exposure of James Bay Cree to methylmercury during pregnancy for the years 1983–91

Since 1982 the Cree Board of Health and Social Services of James Bay (Quebec, Canada) has taken samples of hair from Cree men and women in the course of the methylmercury (MeHg) surveillance program. As a measure of foetal exposure, samples of hair of the mother are taken at the beginning of pregnancy and shortly after birth (to determine exposure at birth) and a blood sample is taken from the umbilical cord blood of the newborn. Of the 2360 births between 1983 and 1991, 25% had all three samples taken, but there was not a single sample for 25% of the births. From 1983–1991, the concentrations of mercury (Hg) at the time of conception, at the time of birth and in the umbilical cord have decreased progressively. There is no relationship between Hg in the umbilical cord blood and the weight of the newborn. As is to be expected there is a relationship between the maternal hair concentration at birth and umbilical cord blood Hg concentration at birth. The relationship is the following: Hg cord blood = 8.53+.88xHg maternal blood equivalent {r=0.623, 95% CI(r) 0.770, 0.769] p<0.001}.