Undergraduate student, Cornell University College of Arts and Sciences, 147 Goldwin Smith Hall, Ithaca, NY 14853, USA.
Child Adolesc Psychiatry Ment Health. 2012 Jan 23;6(1):4. doi: 10.1186/1753-2000-6-4.
Lead is toxic to cognitive and behavioral functioning in children even at levels well below those producing physical symptoms. Continuing efforts in the U.S. since about the 1970s to reduce lead exposure in children have dramatically reduced the incidence of elevated blood lead levels (with elevated levels defined by the current U.S. Centers for Disease Control threshold of 10 μg/dl). The current study examines how much lead toxicity continues to impair the academic achievement of children of New York State, using 2010 test data.
This study relies on three sets of data published for the 57 New York counties outside New York City: school achievement data from the New York State Department of Education, data on incidence of elevated blood lead levels from the New York State Department of Health, and data on income from the U.S. Census Bureau. We studied third grade and eighth grade test scores in English Language Arts and mathematics. Using the county as the unit of analysis, we computed bivariate correlations and regression coefficients, with percent of children achieving at the lowest reported level as the dependent variable and the percent of preschoolers in the county with elevated blood lead levels as the independent variable. Then we repeated those analyses using partial correlations to control for possible confounding effects of family income, and using multiple regressions with income included.
The bivariate correlations between incidence of elevated lead and number of children in the lowest achievement group ranged between 0.38 and 0.47. The partial correlations ranged from 0.29 to 0.40. The regression coefficients, both bivariate and partial (both estimating the increase in percent of children in the lowest achievement group for every percent increase in the children with elevated blood lead levels), ranged from 0.52 to 1.31. All regression coefficients, when rounded to the nearest integer, were approximately 1. Thus, when the percent of children showing elevated lead increases by one percent, the percent of children in the lowest achievement group, according to the regression equations generated, also increases by about one percent. All associations were significant at the 0.05 level.
Despite public health advances, and despite the imprecision of measures, an association between the incidence of elevated blood lead and achievement in New York counties is still apparent, not attributable to confounding by income. Efforts to reduce lead exposure should persist with vigor.
即使在低于导致身体症状的水平，铅也会对儿童的认知和行为功能造成毒害。自 20 世纪 70 年代以来，美国一直在继续努力降低儿童的铅暴露水平，这大大降低了血铅水平升高的发生率（目前美国疾病控制中心的阈值为 10μg/dl）。本研究使用 2010 年的测试数据，检查铅中毒对纽约州儿童学业成绩的影响程度。
本研究依赖于为纽约市以外的 57 个纽约县发布的三组数据：纽约州教育部的学校成绩数据、纽约州卫生部的血铅水平升高发生率数据以及美国人口普查局的收入数据。我们研究了三年级和八年级的英语语言艺术和数学测试成绩。以县为分析单位，我们计算了双变量相关系数和回归系数，以报告的最低水平的儿童比例为因变量，以该县学龄前儿童血铅水平升高的比例为自变量。然后，我们使用偏相关来控制家庭收入的可能混杂影响，以及使用包含收入的多元回归来重复这些分析。
血铅升高发生率与最低成绩组儿童人数之间的双变量相关系数在 0.38 到 0.47 之间。偏相关系数在 0.29 到 0.40 之间。回归系数，无论是双变量还是偏相关（都估计了血铅升高儿童的百分比每增加一个百分点，最低成绩组儿童的百分比增加的数量），在 0.52 到 1.31 之间。所有回归系数，四舍五入到最接近的整数，大约为 1。因此，当显示血铅升高的儿童比例增加一个百分点时，根据生成的回归方程，处于最低成绩组的儿童比例也会增加大约一个百分点。所有关联在 0.05 水平上均具有统计学意义。
尽管公共卫生取得了进展，尽管测量存在不精确性，但在纽约县，血铅升高的发生率与成绩之间仍存在关联，这不是收入混杂造成的。减少铅暴露的努力应继续大力进行。
