Abstract
Background: Arsenic is a known childhood neurotoxicant, but its neurotoxicity at low exposure levels is still not well established. Our cross-sectional study aimed to test the association between low-level arsenic exposure and executive functions (EF) among children in Montevideo. We also assessed effect modification by arsenic methylation capacity, a susceptibility factor for the health effects of arsenic, and by B-vitamin intake, which impacts arsenic methylation. Methods: Arsenic exposure was assessed as the specific gravity-adjusted sum of urinary arsenic metabolites (U-As) among 255 ~7 year-old children, and methylation capacity as the proportion of urinary monomethylarsonic acid (%MMA). B-vitamin intake was calculated from the average of two 24-hour dietary recalls. EF was measured using three tests from the Cambridge Neuropsychological Test Automated Battery - Stockings of Cambridge (SOC), Intra-dimensional/extra-dimensional shift task (IED), and Spatial Span (SSP). Generalized linear models assessed associations between U-As and EF measures, adjusting for age, sex, maternal education, possessions score, Home Observation for Measurement of the Environment Inventory score, season, and school clusters. A “B-vitamin index” was calculated using principalcomponent analysis. Effect modification by the index and urinary %MMA was assessed in strata split at the respective medians of these variables. Results: The median (range) U-As and water arsenic levels were 9.9 µg/L (2.2, 47.7) and 0.45 µg/L (0.1, 18.9) respectively. U-As was inversely associated with the number of stages completed (β = -0.02; 95% CI: -0.03, -0.002) and pre-executive shift errors (β = -0.08; 95% CI: -0.14, -0.02) of the IED task, and span length of the SSP task (β = -0.01; 95% CI: -0.02, -0.004). There was no clear pattern of effect modification by B-vitamin intake or urinary %MMA. Conclusion: Low-level arsenic exposure may adversely affect executive function among children but additional, including longitudinal, studies are necessary to confirm these findings.
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