Wenzl T B, Kriebel D, Eisen E A, Ellenbecker M J
Department of Work Environment, University of Massachusetts Lowell 01854, USA.
Am Ind Hyg Assoc J. 1995 Apr;56(4):341-8. doi: 10.1080/15428119591016953.
Personal monitoring of extremely low frequency magnetic fields was conducted at a large automatic transmission plant for a case-control study of primary brain cancer. Current workers were selected to represent the jobs most commonly held by study subjects. Several exposure indices, corresponding to different plausible biological mechanisms, were computed for each of 81 workers who wore the monitoring instrument for one-half shift. Average exposures covered a range from 0.16 to 46 mG; median exposure was 1.3 mG. Nonparametric correlations were estimated to learn whether all of these indices rise and fall together. Results were mixed, in that indices sensitive to high values showed correlations above 0.7, but other correlations were between 0.4 and 0.6. Different indices may thus identify different groups as "highly" exposed. The authors also tested whether indices based on the fraction of time spent above hypothesized thresholds were accurately predicted by a lognormal model. For 47% of the workers, the observed indices significantly exceeded those predicted by such a model, suggesting that lognormality is not a good model for distributions of individuals' short-term exposures.
在一家大型自动变速器工厂对极低频磁场进行了个人监测，以开展原发性脑癌的病例对照研究。选择当前工人来代表研究对象最常从事的工作。为81名佩戴监测仪器半个班次的工人分别计算了对应不同合理生物学机制的几个暴露指数。平均暴露范围为0.16至46毫高斯；中位暴露为1.3毫高斯。估计了非参数相关性，以了解所有这些指数是否同步升降。结果不一，对高值敏感的指数显示相关性高于0.7，但其他相关性在0.4至0.6之间。因此，不同的指数可能会将不同的群体识别为“高”暴露群体。作者还测试了基于在假设阈值之上花费的时间比例的指数是否能被对数正态模型准确预测。对于47%的工人，观察到的指数显著超过该模型预测的值，这表明对数正态分布不是个体短期暴露分布的良好模型。
