Rappaport Stephen M, Kupper Lawrence L
School of Public Health, University of North Carolina, Chapel Hill, NC, USA.
J Expo Anal Environ Epidemiol. 2004 Jan;14(1):92-107. doi: 10.1038/sj.jea.7500309.
Although studies of occupational exposure to volatile organic compounds (VOCs) often partition variability across groups, and between and within persons, those of environmental exposure to VOCs have not involved such partitioning. Using data from the Environmental Protection Agency's total exposure assessment methodology (TEAM) studies, we partitioned exposure variability across cities, and between and within persons for nine VOCs. The estimated variance components decreased in the order: within-person > between-person > across city. Despite their smaller magnitudes, estimates of between-person and across-city variance components were sufficiently large to provide reasonable contrast for informative epidemiology studies of most VOCs. Estimates of between-person variance components for environmental VOCs were similar to those published for occupational VOCs (groups defined by job and factory). However, estimates of within-person variance components were much greater for environmental VOCs, probably due to the greater diversity of locations (including the workplace) visited by the general public over time. For benzene and perchloroethylene, we used a simple model to calculate numbers of personal measurements required to relate the exposure level to health outcome statistically. About 10 times more personal measurements would be required to investigate perchloroethylene exposure as compared to benzene exposure; this disparity reflects the greater within-subject variability of perchloroethylene data compared to benzene data. We conclude that variability should be partitioned for environmental VOC exposures in much the same manner as for occupational exposures. There should be sufficient variability in the levels of most VOCs across cities and between subjects to provide reasonable contrast for informative epidemiology studies, as we illustrate for exposures to benzene. Yet, epidemiologists should be wary of investigating environmental VOCs without preliminary data with which to estimate the variance structure of exposure variables.
尽管关于职业性接触挥发性有机化合物（VOCs）的研究常常对不同群体之间以及个体内部和个体之间的变异性进行划分，但关于环境中VOCs接触的研究尚未涉及此类划分。利用美国环境保护局总暴露评估方法（TEAM）研究的数据，我们对九个VOCs在不同城市之间以及个体内部和个体之间的暴露变异性进行了划分。估计的方差分量按以下顺序递减：个体内部＞个体之间＞城市之间。尽管个体之间和城市之间的方差分量估计值较小，但对于大多数VOCs的信息性流行病学研究而言，其大小足以提供合理的对比。环境VOCs的个体之间方差分量估计值与已发表的职业性VOCs（按工作和工厂定义的群体）的估计值相似。然而，环境VOCs的个体内部方差分量估计值要大得多，这可能是由于随着时间推移，普通公众访问的地点（包括工作场所）更加多样化。对于苯和全氯乙烯，我们使用一个简单模型来计算将暴露水平与健康结果进行统计学关联所需的个人测量次数。与苯暴露相比，研究全氯乙烯暴露所需的个人测量次数大约多10倍；这种差异反映了全氯乙烯数据相比苯数据在个体内部具有更大的变异性。我们得出结论，对于环境VOCs暴露，应与职业暴露一样以大致相同的方式划分变异性。正如我们对苯暴露所说明的那样，大多数VOCs在不同城市之间以及个体之间的水平应该有足够的变异性，以便为信息性流行病学研究提供合理的对比。然而，流行病学家在没有初步数据来估计暴露变量的方差结构的情况下，对研究环境VOCs应持谨慎态度。
