Neurodevelopment of Amazonian Infants: Antenatal and Postnatal Exposure to Methyl- and Ethylmercury

Abstract

Neurodevelopment as Gesell development scores (GDSs) in relation to mercury exposure in infants (<6 months of age) of one urban center and two rural villages, respectively, of fisherman and cassiterite miners. Mean total hair-Hg (HHg) concentrations of infants from Itapuã (3.95±1.8 ppm) were statistically (P=0.0001) different from those of infants from Porto Velho (3.84±5.5 ppm) and Bom Futuro (1.85±0.9 ppm). Differences in vaccine coverage among these populations resulted in significantly higher (P=0.0001) mean ethylmercury (EtHg) exposure in urban infants (150 μg) than in infants from either village (41.67 μg, Itapuã; 42.39 μg, Bom Futuro). There was an inverse significant (Spearmanr=−0.2300;P=0.0376) correlation between HHg and GDS for infants from Porto Velho, but not for the rural infants from Bom Futuro (Spearmanr=0.1336;P=0.0862) and Itapuã (Spearmanr=0.1666;P=0.5182). Logistic regression applied to variables above or below the median GDS showed that EtHg exposure (estimatedprobability=−0.0157;P=0.0070) and breastfeeding score (estimatedprobability=−0.0066;P=0.0536) score were significantly associated with GDS.Conclusion. In nurslings whose mothers are exposed to different levels of fish-MeHg (HHg), a higher score of neurological development at six months was negatively associated with exposure to additional TCV-EtHg. Results should be interpreted with caution because of unaccounted variables.