Gump Brooks B, Dykas Matthew J, MacKenzie James A, Dumas Amy K, Hruska Bryce, Ewart Craig K, Parsons Patrick J, Palmer Christopher D, Bendinskas Kestutis
Department of Public Health, Food Studies, and Nutrition, Syracuse University, United States.
Department of Psychology, State University of New York College at Oswego, United States.
Environ Res. 2017 Oct;158:576-582. doi: 10.1016/j.envres.2017.06.033. Epub 2017 Jul 15.
The potential harm from exposure to nonessential metals, particularly mercury (Hg) and lead (Pb), has been the focus of research for years. Initial interest focused on relatively high exposures; however, recent evidence suggests that even background exposures might have adverse consequences for child development. Identifying the extent of these consequences is now a priority.
We assessed blood Pb and Hg levels in a biracial sample of 9-11 year-old children (N = 203). Neurodevelopment and psychological functioning assessments included hostility, disruptive behaviors, emotion regulation, and autism spectrum disorder behaviors. Parasympathetic (vagal) responses to acute stress were indexed by heart rate variability (HRV) at rest and during stress.
With increasing Pb levels, children exhibit higher levels of hostile distrust and oppositional defiant behaviors, were more dissatisfied and uncertain about their emotions, and had difficulties with communication. These significant associations were found within a range of blood Pb levels from 0.19 to 3.25μg/dL, well below the "reference value" for children of >5μg/dL. Vagal reactivity interacted with Hg such that increasing Hg was associated with increasing autism spectrum behaviors for those children with sustained vagal tone during acute stress.
This study is the first to demonstrate an association between very low-level Pb exposure and fundamental psychological mechanisms that might explain prior associations with more complex outcomes such as delinquency. Analyses of vagal reactivity yielded entirely novel associations suggesting that Hg may increase autism spectrum behaviors in children with sustained vagal tone during acute stress. The novelty of these later findings requires additional research for confirmation and the cross-sectional nature of the data caution against assumptions of causality without further research.
接触非必需金属，尤其是汞（Hg）和铅（Pb）所带来的潜在危害多年来一直是研究的焦点。最初的研究兴趣集中在相对较高的暴露水平；然而，最近的证据表明，即使是背景暴露也可能对儿童发育产生不良后果。确定这些后果的程度现在是一个优先事项。
我们评估了203名9至11岁儿童的双种族样本中的血铅和血汞水平。神经发育和心理功能评估包括敌意、破坏性行为、情绪调节和自闭症谱系障碍行为。通过静息和应激期间的心率变异性（HRV）来衡量副交感神经（迷走神经）对急性应激的反应。
随着血铅水平的升高，儿童表现出更高水平的敌意不信任和对立违抗行为，对自己的情绪更加不满和不确定，并且在沟通方面存在困难。这些显著关联在血铅水平为0.19至3.25μg/dL的范围内被发现，远低于儿童>5μg/dL的“参考值”。迷走神经反应性与汞相互作用，使得对于那些在急性应激期间迷走神经张力持续的儿童，汞含量增加与自闭症谱系行为增加相关。
本研究首次证明了极低水平的铅暴露与基本心理机制之间的关联，这可能解释了先前与诸如犯罪等更复杂结果的关联。对迷走神经反应性的分析产生了全新的关联，表明汞可能会增加急性应激期间迷走神经张力持续的儿童的自闭症谱系行为。这些后期发现的新颖性需要更多研究来证实，并且数据的横断面性质提醒在没有进一步研究的情况下不要假设因果关系。
