Chang Soju, Crothers Carol, Lai Shenghan, Lamm Steven
Johns Hopkins University, Bloomberg School of Public Health, Baltimore, Maryland, USA.
Birth Defects Res A Clin Mol Teratol. 2003 Oct;67(10):886-92. doi: 10.1002/bdra.10089.
Contamination of drinking water with perchlorate, a known thyrotropic agent, has been demonstrated in areas in the western United States. The health consequences of that exposure have been studied, particularly in the State of Nevada. Previous studies in Nevada, comparing the area with perchlorate in the drinking water and the areas without perchlorate in the drinking water, have found no difference in neonatal thyroxine (T(4)) or thyrotropin (TSH) levels, or in the prevalences of thyroid diseases and thyroid cancer. This same study design has now been applied to the major neurobehavioral diseases of childhood (i.e., attention deficit-hyperactivity disorder (ADHD) and autism) and to school performance in order to determine whether those conditions are more frequent in the area with perchlorate-contaminated water.
Medical services data on ADHD and autism were obtained from the Nevada Medicaid system for the period of January 1, 1996, to December 31, 2000, with county of residence used as the basis for residential information. Analyses of fourth-grade school performance results for two recent time periods came from the state government. Perchlorate concentrations in drinking water had been determined by local water authorities. ADHD and autism rates for the area with perchlorate in the drinking water (Clark County) were calculated and compared with the rates for the other areas in the state, as were fourth-grade school performances.
Analysis of the data from the Nevada Medicaid program shows that the rates for ADHD and for autism in the area where perchlorate was in the drinking water did not exceed the rates in those areas where there was no perchlorate contamination in the drinking water. Fourth-grade standardized test results for students in Clark County were not different from those of the remainder of the state.
This ecological study of children in the exposure area did not find evidence of an increased risk of either ADHD or of autism caused by perchlorate contamination in the drinking water. Furthermore, no difference in overall fourth-grade school performance was observed. No evidence was found that children from the area with perchlorate in the drinking water (up to 24 microg/liter) had either an increase in pediatric neurobehavioral disease (ADHD and autism) or a decrease in fourth-grade academic performance. The limitations of this ecological study relate to diagnostic criteria and ascertainment of geographic and demographic differences and to data on individual residence and water consumption during pregnancy.
美国西部一些地区的饮用水已被证明受到高氯酸盐污染，高氯酸盐是一种已知的促甲状腺素物质。人们已对这种暴露的健康后果进行了研究，尤其是在内华达州。内华达州此前的研究比较了饮用水中含有高氯酸盐的地区和饮用水中不含高氯酸盐的地区，发现新生儿甲状腺素（T(4)）或促甲状腺激素（TSH）水平、甲状腺疾病和甲状腺癌的患病率并无差异。现在，同样的研究设计已应用于儿童的主要神经行为疾病（即注意力缺陷多动障碍（ADHD）和自闭症）以及学业成绩，以确定这些病症在饮用水受高氯酸盐污染的地区是否更为常见。
从内华达州医疗补助系统获取了1996年1月1日至2000年12月31日期间有关ADHD和自闭症的医疗服务数据，以居住县作为居住信息的依据。对最近两个时间段四年级学业成绩结果的分析来自州政府。当地水务部门已测定了饮用水中的高氯酸盐浓度。计算了饮用水中含有高氯酸盐的地区（克拉克县）的ADHD和自闭症发病率，并与该州其他地区的发病率进行了比较，四年级学业成绩也进行了同样的比较。
对内华达州医疗补助项目数据的分析表明，饮用水中含有高氯酸盐的地区的ADHD和自闭症发病率并未超过饮用水中无高氯酸盐污染地区的发病率。克拉克县学生的四年级标准化考试成绩与该州其他地区的成绩没有差异。
这项对暴露地区儿童的生态学研究未发现证据表明饮用水中的高氯酸盐污染会增加ADHD或自闭症的风险。此外，未观察到四年级总体学业成绩有差异。未发现证据表明饮用水中含有高氯酸盐的地区（高达24微克/升）的儿童患有儿科神经行为疾病（ADHD和自闭症）的几率增加或四年级学业成绩下降。这项生态学研究的局限性涉及诊断标准、地理和人口差异的确定以及孕期个人居住和用水量数据。
