THE SEYCHELLES CHILD-DEVELOPMENT STUDY - RESULTS AND NEW DIRECTIONS THROUGH 29 MONTHS

The Seychelles Child Development Study was begun in 1986 to prospectiv ely examine the association between child development and prenatal and postnatal methylmercury exposure from a high fish diet. Hair mercury levels from mothers and children are used as the index of exposure. A cross-sectional Pilot Study of 789 infants suggested that prenatal mer cury exposure may affect development and that the effect decreased wit h age independently of exposure. A follow up of 217 Pilot Study childr en at 66 months of age also suggested that neurodevelopmental effects of prenatal exposure might be present, but the associations were depen dent on outcomes in a small number of children. On the basis of the in itial results of the Pilot Study a prospective, longitudinal Main Stud y, with more data on confounding variables and more extensive developm ental testing, was begun on a new cohort of 779 children. No associati on between prenatal exposure and primary neurodevelopmental outcomes w as seen at 6 1/2, 19, or 29 months of age. There was an inverse relati onship at 29 months in boys only between maternal hair mercury level a nd activity level, as judged by the examiner during the testing sessio n (one of seven behavioral subscales of the Infant Behavior Record, of the Bayley Scales of Infant Development). In addition to an interacti on between maternal hair level and gender, subsequent, secondary analy ses are examining interactions between mercury level and a number of s ocioeconomic factors. Secondary analyses of developmental milestones, similar to those used in the Iraq study, are also under way. Although the association with activity suggests the need for further study of t his cohort, no definite adverse neurodevelopmental effects from fetal mercury exposure have been detected through 29 months of age. In a rel ated study, brains were obtained at autopsy from thirty-two Seychelloi s infants. Tissue from six different brain regions was examined histol ogically and analyzed for mercury. No definite histological abnormalit ies were found. Mercury levels ranged from about 50 ppb to 300 ppb and there was good correlation among brain regions. For 27 brains materna l hair from delivery was available and maternal hair mercury levels co rrelated well with levels in infant brain.