Sahl J D, Kelsh M A, Smith R W, Aseltine D A
Southern California Edison Company, Occupational Research Division, Rosemead 91770.
Bioelectromagnetics. 1994;15(1):21-32. doi: 10.1002/bem.2250150107.
Research that has attempted to examine the relationship between work exposures to magnetic fields and health effects has suffered from limited exposure information. Power-frequency electric and magnetic (EM) field exposures vary substantially between industries, occupations, and individuals. In this study magnetic field data were collected for a variety of occupational categories within an electric utility. The sampling procedures emphasized craft occupations that were presumed to have higher exposures to magnetic fields. The objectives were to provide better exposure information for an ongoing cancer mortality study, examine the relationship between different summary measures of magnetic field exposure, and make available descriptive information useful for exposure reduction and worker education. Principal components analysis (PCA) and Varimax rotation were used to explore the relationships between the different summary measures among all utility workers and among the subset of electrical craft occupations. Discriminant analysis was used to assess summary measures of exposure that differentiated occupational groups. Measurements for 770 days generated a total of 42378 hours of magnetic field data. Eleven summary indices of exposure were calculated for specific occupational groups. These include arithmetic mean, geometric mean, median, 95th and 99th percentiles, and fraction of measurements exceeding .5, 1, 5, 10, and 100 microT. Electrical craft occupations had higher work exposures than non-craft occupations. Electricians and substation operators had the highest exposures among craft occupations. We identified subsets of summary measures that were intercorrelated. The first PCA axis included the geometric mean, median, and the fractions exceeding 0.5 and 1.0 microT. This set of measures also were best at discriminating occupational groups. The relevance of these findings may become more important if consistent associations are found between particular occupations and disease and particular occupations and magnetic field summary measures. Further research is needed to evaluate these exposure assessment findings.
试图研究工作中接触磁场与健康影响之间关系的研究，一直受到接触信息有限的困扰。工频电场和磁场（EM）暴露在不同行业、职业和个体之间差异很大。在本研究中，收集了一家电力公司内各种职业类别的磁场数据。抽样程序重点关注那些被认为接触磁场程度较高的技术工种。目的是为正在进行的癌症死亡率研究提供更好的接触信息，研究磁场暴露的不同汇总指标之间的关系，并提供有助于减少接触和对工人进行教育的描述性信息。主成分分析（PCA）和方差最大化旋转被用于探索所有电力公司工人以及电气技术工种子集中不同汇总指标之间的关系。判别分析用于评估区分职业群体的接触汇总指标。770天的测量共产生了42378小时的磁场数据。针对特定职业群体计算了11个接触汇总指数。这些指数包括算术平均值、几何平均值、中位数、第95和第99百分位数，以及超过0.5、1、5、10和100微特斯拉的测量值比例。电气技术工种的工作接触高于非技术工种。电工和变电站操作员在技术工种中接触程度最高。我们确定了相互关联的汇总指标子集。主成分分析的第一个轴包括几何平均值、中位数以及超过0.5和1.0微特斯拉的比例。这组指标在区分职业群体方面也表现最佳。如果在特定职业与疾病以及特定职业与磁场汇总指标之间发现一致的关联，这些发现的相关性可能会变得更加重要。需要进一步研究来评估这些接触评估结果。
