Re: Electromagnetic fields, polychlorinated biphenyls, and prostate cancer mortality in electric utility workers - reply.
Am J Epidemiol 2003 Nov; 158(9):929
In his letter to the editor, Dr. Mezei (1) raises an important issue regarding a limitation of our study (2), which investigated risk factors for prostate cancer mortality rather than incidence. Although the distinction between cancer incidence and mortality is likely to be familiar to most readers of the Journal, we acknowledge that prostate cancer mortality is affected by various factors, including the ones cited by Dr. Mezei, and agree that a short description of the limitations of mortality data in our study would have been helpful to some readers. However, we disagree with his assertion that "the value and interpretation of the results are questionable" (1, p. 929) because the study was based on mortality data. For differential survival to confound associations of prostate cancer with exposure to magnetic fields, substantial differences in prostate cancer survival would have to be associated with cumulative exposure. However, our analyses included only those workers employed by five large companies within a single industry. Large differences in culture and socioeconomic position are less likely to confound associations in such internal comparisons than in community-based studies that sample from the population at large. Moreover, access to medical care is likely to be relatively uniform within a cohort of workers from the same industry. Undoubtedly, additional studies designed to control for biases from several sources would have to be conducted before it can be concluded that electromagnetic field exposure is an etiologic agent for prostate cancer development. Our study (2) makes an important contribution to the literature on prostate cancer mortality, and it adds another layer to the foundation of studies from which epidemiologists and laboratory scientists can build to further investigate whether a causal relation exists between exposure to electromagnetic fields and development of prostate cancer.
Prostate-cancer; Electromagnetic-fields; Epidemiology; Polychlorinated-biphenyls; Mortality-data; Electrical-industry; Electrical-workers; Occupational-exposure; Neoplasms; Racial-factors
National Institute for Occupational Safety and Health, Health Effects Laboratory Division, 1095 Willowdale Road, Morgantown, WV 26505
American Journal of Epidemiology