SEMIPARAMETRIC MODELING OF AGE AT ACHIEVING DEVELOPMENTAL MILESTONES AFTER PRENATAL EXPOSURE TO METHYLMERCURY IN THE SEYCHELLES CHILD-DEVELOPMENT STUDY

Controversy exists concerning the fetal risk associated with exposure to low-dose methylmercury from maternal fish consumption. Previous stu dies of the effects of acute prenatal mercury exposure identified dela ys in achieving developmental milestones among exposed children. This led to public health concern that prenatal low-dose exposure from fish consumption could adversely affect the fetus. We evaluated the effect s of prenatal methylmercury exposure (through maternal fish consumptio n) on the age that children walked and first said words in the main st udy cohort of the Seychelles Child Development Study. We used semipara metric generalized additive models to identify nonlinearities in the r elationships between prenatal exposure and developmental outcomes, aft er adjusting for covariates, and to evaluate their importance. Very sl ight delays (<1 day) in walking were seen as mercury levels increased from 0 to 7 ppm, but this effect did not persist at the higher exposur e levels represented by the cohort, making it difficult to conclude th at a cause and effect relationship existed at the exposure levels seen in this cohort. There was no evidence for any association between pre natal exposure and age at talking.