Objective

Arsenic is a known childhood neurotoxicant, but its neurotoxicity at low exposure levels is still not well established. The aim of our cross-sectional study was 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). Arsenic concentrations from kitchen water samples at participants’ homes were assessed. 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 the association between U-As and EF measures; models were adjusted for age, sex, maternal education, possessions score, Home Observation for Measurement of the Environment Inventory score, season, and school clusters. Additional analyses were conducted to address issues of residual confounding and sample size. A “B-vitamin index” was calculated using principal component 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, indicating that exposure originated mainly from other sources. 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.

中文翻译：

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来自乌拉圭蒙得维的亚的在学儿童及其与低水平砷暴露同时发生的儿童的执行功能。

目的

砷是一种已知的儿童神经毒剂，但在低暴露水平下其神经毒性仍未完全确定。我们横断面研究的目的是测试蒙得维的亚儿童中低水平砷暴露与执行功能（EF）之间的关联。我们还评估了通过砷甲基化能力（影响砷对健康的敏感性的因素）和通过影响维生素A甲基化的B维生素摄入量对效果的影响。

方法

砷暴露被评估为255〜7岁儿童中尿砷代谢物（U-As）的比重调整后总和，而甲基化能力则以尿单甲基ar酸（％MMA）的比例进行评估。评估参与者家中厨房水样中的砷浓度。维生素B摄入量是根据两次24小时饮食召回的平均值计算得出的。EF是使用来自剑桥神经心理学测试自动电池–剑桥长袜（SOC），维内/维外移位任务（IED）和空间跨度（SSP）的三项测试测量的。广义线性模型评估了U-As和EF措施之间的关联；对年龄，性别，孕产妇教育，财产得分，环境清单测量的家庭观察得分，季节和学校类别进行了调整。进行了其他分析，以解决残留混杂和样本量的问题。使用主成分分析法计算“ B维生素指数”。在这些变量各自的中位数，在分层中评估了通过指数和尿％MMA引起的效果改善。

结果

U-As和水中砷的中位数（范围）分别为9.9 µg / L（2.2，47.7）和0.45 µg / L（0.1，18.9），表明该暴露主要来自其他来源。U-As与完成的阶段数（β= -0.02; 95％CI：-0.03，-0.002）和执行前换档误差（β= -0.08; 95％CI：-0.14，-0.02）成反比IED任务的时间间隔和SSP任务的跨度（β= -0.01； 95％CI：-0.02，-0.004）。没有明确的摄入维生素B或尿％MMA的效果改变模式。

结论

低水平的砷暴露可能会对儿童的执行功能产生不利影响，但必须进行其他研究（包括纵向研究）以证实这些发现。