Background

Manganese (Mn) is an element found in the environment and certain geographic areas have elevated concentrations in soil and water du to natural conditions or anthropic activities. A growing body of data suggests that exposure to manganese in drinking water could be neurotoxic.

Objective

Firstly, we aimed to examine the association between exposure to manganese from drinking water and cognition in children consuming well water. Secondly, we also aimed to examine the relation between cognition and manganese concentrations in children’s hair, nail, and saliva.

Methods

A total 259 children from 189 households consuming well water were included in the present study (ages 5.9 to 13.7 years). We assessed children’s cognition with the WISC-IV, and we used five indicators of manganese exposure: concentration in tap water, intake from the consumption of water divided by child’s weight, manganese concentration in children’s hair, toe nail, and saliva. We used General Estimating Equation analysis to assess the relation between manganese exposure indicators and IQ scores, adjusting for potential confounders, and taking into account family clusters.

Results

Drinking water manganese concentrations were generally low, with 48% of children consuming water <5 μg/L, 25% >50 μg/L, and 4% >400 μg/L. Results differed by sex. In girls, higher manganese concentration in water, hair, and toe nail were associated with poorer Performance IQ scores but this was significant only for toe nail (for a 10-fold increase in manganese, β: −5.65, 95% CIs: −10.97, −0.32). Opposite associations were observed in boys, i.e., better Performance IQ scores with higher manganese concentration hair, toe nail, and water, the latter being significant (β: 2.66, 95% CIs: 0.44, 4.89). Verbal IQ scores did not seem to be associated with manganese exposure indicators.

Conclusions

Drinking water manganese levels were considerably lower than in previous studies reporting neurotoxic effects. There was no clear indication of an association between exposure to manganese and cognitive development in this sample of school-age children although the data suggest there might be sex-specific associations. Given the low levels of exposure and sex-specific associations, a larger sample size would have been required to increase the statistical power and better characterize the relations.

中文翻译：

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学龄儿童的饮用水和锰认知水平低

背景

锰（Mn）是一种在环境中发现的元素，某些地理区域由于自然条件或人类活动而在土壤和水中的浓度升高。越来越多的数据表明，饮用水中锰的暴露可能具有神经毒性。

客观的

首先，我们旨在研究饮用水中锰的暴露与食用井水的儿童的认知之间的关系。其次，我们还旨在检验认知能力与儿童头发，指甲和唾液中锰含量之间的关系。

方法

本研究纳入了来自189个家庭的井水的259名儿童（年龄5.9至13.7岁）。我们使用WISC-IV评估了儿童的认知能力，并使用了五种锰暴露指标：自来水浓度，水消耗量除以儿童体重，儿童头发，脚趾甲和唾液中锰的含量。我们使用一般估计方程分析来评估锰暴露指标与智商得分之间的关​​系，调整潜在的混杂因素，并考虑到家庭聚类。

结果

饮用水中的锰含量普遍较低，其中48％的儿童饮水<5μg/ L，25％> 50μg/ L和4％> 400μg/ L。结果因性别而异。在女孩中，锰在水中，头发和脚趾甲中的浓度较高与性能智商得分较低相关，但这仅对脚趾甲才有意义（锰增加10倍，β：−5.65，95％CI：−10.97 ，-0.32）。在男孩中观察到相反的关联，即较高的锰浓度的头发，脚趾甲和水的绩效IQ得分更高，后者显着（β：2.66，95％CI：0.44，4.89）。口头智商得分似乎与锰暴露指标无关。

结论

饮用水中的锰含量大大低于先前报告的神经毒性作用的研究。尽管数据表明可能存在特定性别的关联，但在这个学龄儿童样本中，没有明确的迹象表明锰暴露与认知发育之间存在关联。鉴于低水平的接触和特定性别的关联，将需要更大的样本量以增加统计能力并更好地表征这种关系。