| Examination of the Melatonin Hypothesis in Women Exposed at Night to EMF or Bright Light Charles Graham, Mary R. Cook, Mary M. Gerkovich, and Antonio Sastre Midwest Research Institute, Kansas City, Missouri, USA Abstract
It has been hypothesized that the increased incidence of breast cancer in industrial societies is related to greater exposure to power-frequency electric and magnetic fields (EMF) and/or the presence of high levels of light at night (LAN) . EMF and LAN are said to reduce circulating levels of the hormone melatonin which, in turn, allows estrogen levels to rise and stimulate the turnover of breast epithelial stem cells and increase the risk for malignant transformation. Three laboratory-based studies, in which a total of 53 healthy young women were exposed at night to EMF or to LAN under controlled exposure conditions, were performed to determine whether such exposures reduce melatonin and are associated with further alterations in estrogen. All-night exposure to industrial-strength magnetic fields (60 Hz, 28.3 µT) had no effect on the blood levels of melatonin or estradiol. In contrast, nocturnal melatonin levels were profoundly suppressed, and the time of peak concentration was significantly delayed in women exposed to LAN, regardless of whether they were in the follicular or luteal phase of the menstrual cycle. These changes, however, were not associated with alterations in point-for-point matching measures of estradiol. Women who chronically secrete high or low amounts of melatonin each night (area-under-curve range: 86-1,296 pg/mL) also did not differ in their blood levels of estradiol. Taken together, these results are consistent with a growing body of evidence which generally suggests that environmental EMF exposure has little or no effect on the parameters measured in this report. Key words: breast cancer, electromagnetic fields, estrogen levels, light at night, melatonin, neuroendocrine, reproductive hormones, women's health. Environ Health Perspect 109:501-507 (2001) . [Online 9 May 2001] http://ehpnet1.niehs.nih.gov/docs/2001/109p501-507graham/ abstract.html Address correspondence to C. Graham, Midwest Research Institute, 425 Volker Boulevard, Kansas City, MO 64110 USA. Telephone: (816) 753-7600, ext. 1161. Fax: (816) 753-7380. E-mail: cgraham@mriresearch.org We thank D.W. Riffle, S.J. Hoffman, M. Gibertini, D.K. Smith, D.I.L. Dozier, K.E. Kakolewski, and B.J. Peterson for their valuable help in data collection and analysis. Research funding was provided by the National Institute of Environmental Health Sciences (grant ES 07053) . Received 14 September 2000 ; accepted 30 November 2000.
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