The relationship between electromagnetic field and light exposures to melatonin and breast cancer risk: A review of the relevant literature

Worldwide, breast cancer is the most common malignancy accounting for 20-32 % of all female cancers. This review summarizes the peer-reviewed, publishe d data pertinent to the hypothesis that increased breast cancer in industri alized countries is related to the increased use of electricity [Stevens, R .G., S, Davis 1996], That hypothesis specifically proposes that increased e xposure to light at night and electromagnetic fields (EMF) reduce melatonin production. Because some studies have shown that melatonin suppresses mamm ary tumorigenesis in rats and blocks estrogen-induced proliferation of huma n breast cancer cells in vitro, it is reasoned that decreased melatonin pro duction leads to increased risk of breast cancer. To evaluate this hypothes is, the paper reviews epidemiological data on associations between electric ity and breast cancer, and assesses the data on the effects of EMF exposure on melatonin physiology in both laboratory animals and humans, In addition , the results on the effects of melatonin on in vivo carcinogenesis in anim als are detailed along with the controlled in vitro studies on melatonin's effects on human breast cancer cell lines. The literature is evaluated for strength of evidence, inter-relationships between various lines of evidence , and gaps in our knowledge. Based on the published data, it is currently u nclear if EMF and electric light exposure are significant risk factors for breast cancer, but further study appears warranted. Given the ubiquitous na ture of EMF and artificial light exposure along with the high incidence of breast cancer, even a small risk would have a substantial public health imp act.