Savitz D A, Wachtel H, Barnes F A, John E M, Tvrdik J G
Department of Epidemiology, School of Public Health, University of North Carolina, Chapel Hill 27599.
Am J Epidemiol. 1988 Jul;128(1):21-38. doi: 10.1093/oxfordjournals.aje.a114943.
Concern with health effects of extremely low frequency magnetic fields has been raised by epidemiologic studies of childhood cancer in relation to proximity to electric power distribution lines. This case-control study was designed to assess the relation between residential exposure to magnetic fields and the development of childhood cancer. Eligible cases consisted of all 356 residents of the five-county 1970 Denver, Colorado Standard Metropolitan Statistical Area aged 0-14 years who were diagnosed with any form of cancer between 1976 and 1983. Controls were selected by random digit dialing to approximate the case distribution by age, sex, and telephone exchange area. Exposure was characterized through in-home electric and magnetic field measurements under low and high power use conditions and wire configuration codes, a surrogate measure of long-term magnetic field levels. Measured magnetic fields under low power use conditions had a modest association with cancer incidence; a cutoff score of 2.0 milligauss resulted in an odds ratio of 1.4 (95% confidence interval (CI) = 0.6-2.9) for total cancers and somewhat larger odds ratios (ORs) for leukemias (OR = 1.9), lymphomas (OR = 2.2), and soft tissue sarcomas (OR = 3.3). Neither magnetic fields (OR = 1.0) nor electric fields (OR = 0.9) under high power use conditions were related to total cancers. Wire codes associated with higher magnetic fields were more common among case than control homes. The odds ratio to contrast very high and high to very low, low, and buried wire codes was 1.5 (95% CI = 1.0-2.3) for total cases, with consistency across cancer subgroups except for brain cancer (OR = 2.0) and lymphomas (OR = 0.8). Contrasts of very high to buried wire code homes produced larger, less precise odds ratios of 2.3 for total cases, 2.9 for leukemias, and 3.3 for lymphomas. Adjusted estimates for measured fields and wire codes did not differ from crude results, indicating an absence of confounding. Limitations to the study are nonresponse (especially for field measurements), differential mobility of cases and controls, and a presumably nondifferential exposure misclassification from the use of imperfect surrogates for long-term magnetic field exposure history. In spite of these concerns, the results encourage further examination of the carcinogenic potential from this form of nonionizing radiation.
关于极低频磁场对健康影响的关注源于对儿童癌症与靠近输电线关系的流行病学研究。这项病例对照研究旨在评估居住环境中磁场暴露与儿童癌症发生之间的关系。符合条件的病例包括1970年科罗拉多州丹佛市标准大都市统计区五县内所有年龄在0至14岁之间、于1976年至1983年期间被诊断患有任何形式癌症的356名居民。对照组通过随机数字拨号选取，以使其在年龄、性别和电话交换区方面的分布与病例组相近。通过在低功率和高功率使用条件下进行的家庭电场和磁场测量以及电线配置代码（长期磁场水平的替代指标）来表征暴露情况。低功率使用条件下测得的磁场与癌症发病率有适度关联；以2.0毫高斯为临界值，所有癌症的比值比为1.4（95%置信区间（CI）=0.6 - 2.9），白血病（比值比 = 1.9）、淋巴瘤（比值比 = 2.2）和软组织肉瘤（比值比 = 3.3）的比值比略高。高功率使用条件下的磁场（比值比 = 1.0）和电场（比值比 = 0.9）均与所有癌症无关。与较高磁场相关的电线代码在病例家庭中比在对照家庭中更为常见。将极高和高电线代码与极低、低和埋线代码进行对比时，所有病例的比值比为1.5（95%CI = 1.0 - 2.3），除脑癌（比值比 = 2.0）和淋巴瘤（比值比 = 0.8）外，各癌症亚组结果一致。将极高电线代码家庭与埋线代码家庭进行对比时，所有病例的比值比更大但不太精确，分别为2.3、白血病为2.9、淋巴瘤为3.3。对测得的磁场和电线代码进行调整后的估计值与粗略结果无差异，表明不存在混杂因素。该研究的局限性包括无应答（尤其是磁场测量方面）、病例组和对照组的不同流动性以及由于使用不完美的长期磁场暴露历史替代指标可能导致的非差异性暴露错误分类。尽管存在这些问题，研究结果仍鼓励进一步研究这种非电离辐射形式的致癌潜力。
