Semiparametric modeling of age at achieving developmental milestones after prenatal exposure to methylmercury in the Seychelles child development study.

Abstract

Controversy exists concerning the fetal risk associated with exposure to low-dose methylmercury from maternal fish consumption. Previous studies of the effects of acute prenatal mercury exposure identified delays 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 effects of prenatal methylmercury exposure (through maternal fish consumption) on the age that children walked and first said words in the main study cohort of the Seychelles Child Development Study. We used semiparametric generalized additive models to identify nonlinearities in the relationships between prenatal exposure and developmental outcomes, after adjusting for covariates, and to evaluate their importance. Very slight 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 exposure levels represented by the cohort, making it difficult to conclude that a cause and effect relationship existed at the exposure levels seen in this cohort. There was no evidence for any association between prenatal exposure and age at talking.

Prenatal Methylmercury Exposure and Developmental Outcomes: Review of the Evidence and Discussion of Future Directions

“…This was considered a pilot study by the authors, although a large amount of data was collected of a good standard and was therefore reported. A subsequent study commenced in the Seychelle Islands in 1989 with a sample of newborns who were followed up at ages 6.5 months, 19 months, 29 months, 66 months, and 108 months ( Axtell et al 1998 , 2000 ; Cernichiari et al 1995b ; Cox et al 1999 ; Crump et al 2000 ; Davidson et al 1995a , 1995b , 1998 , 1999b , 2001 ; Myers et al 1995c , 1995d , 1997 , 2000 , 2003 ; Palumbo et al 2000 ). Sample sizes in the longitudinal studies were larger than those in the cross-sectional studies ( Tables 1 and 2 ), although there was inevitable attrition over the periods of longitudinal investigation ( Table 2 ).…”

Occupational and Environmental Toxicology of Mercury and Its Compounds.

“…In the Seychelles Islands, the developmental effects of low level methylmercury exposure in utero from consumption of marine fish by mothers have also been studied [54][55][56][57][58][59][60][61][62][63][64][65][66] . An association between in utero mercury exposure was found for DDST-R(evised) abnormal plus questionable scores combined 62) .…”