AUTHORS: D.P. Loomis et al.
Journal
of the National Cancer Institute. 1994:86(12) p. 921-925.
STUDY DESIGN: To test the hypothesis that exposure to magnetic fields causes female breast cancer, a case-control study based on U.S. mortality data was conducted. The study population included women at least 20 years old who resided and died between 1985 and 1989 in one of the 24 states where death certificate records occupation and industry codes. Cases included women whose underlying cause of death was breast cancer. Four controls were randomly selected for each case, where a control was defined as a woman whose underlying cause of death was not breast cancer, leukemia, or brain cancer. The study population was comprised of 68 cases and 199 controls with electrical occupations and 27,814 cases and 110,750 controls with "other" occupations. Exposure assessment was based on occupation recorded on the death certificate.
CONCLUSIONS: After adjustment for age, race, and social class, women with electrical occupations demonstrated excess mortality from breast cancer (OR=1.38, 95% CI=1.04- 1.82). Seven other occupations held more frequently by women and involving a potential for increased electric exposure were also analyzed. No excess mortality due to breast cancer was found in this group which included occupations such as telephone operators, data entry operators and computer operators.
LIMITATIONS: Although death certificate information relating to breast cancer as an underlying cause of death is very reliable, death-certificate-occupational data without further follow-up is of limited value. The absence of any direct exposure assessment severely limits inferences that can be drawn from this study. Women dying of breast cancer are also not representative of women diagnosed with breast cancer, which may also be a source of bias.