A new meta-analysis of 15 studies published between 2000 and 2009 has found no association between exposure to extremely low-frequency electromagnetic fields (ELF-EMFs) and risk of breast cancer. The best known sources of ELF-EMFs are electric power generation facilities and transmission lines. The meta-analysis was performed using studies obtained in a search of the Medline, PubMed, Embase, the Cochrane Library, and Web of Science databases. The analysis incorporated data concerning 24,338 female breast cancer cases and 60,628 cancer free controls.
No significant association between ELF-EMF exposure and risk of breast cancer was found overall. Nor were any associations found when the women were categorized by ELF-EMF exposure modes, menopausal status, and estrogen receptor status. The authors conclude that ELF-EMF exposure has no association with risk of breast cancer in women.
No major studies have found an association
No major recent studies have found an association between proximity to power lines or other sources of extremely low frequency fields and breast cancer. However, this topic continues to be studied since a link appears plausible to some observers (in part because an association with childhood leukemia has not been ruled out).
ELF-EMFs induce very weak electric currents in the human body. However, unlike x-rays and CT scans, the fields are not capable of breaking chemical bonds, including DNA bonds (i.e., ELF-EMFs are a source of non-ionizing radiation). Therefore, the proposed mechanisms of action include the following hypotheses: (1) ELF-EMFs act in concert with one or more other breast cancer promoters as a cocarcinogenic factor; (2) ELF-EMFs influence the melatonin system in a way that increases breast cancer risk (EMFs have been shown to suppress the production of melatonin by the pineal glands of mammals); (3) ELF-EMFs might alter some cancer-related cell functions, such as cell proliferation and intercellular communication; and (4) exposure to ELF-EMFs might increase the promotion of free radicals (thereby increasing cell damage) or interfere with calcium channels.
Nevertheless, it makes sense to us that radiation that is too weak to cause damage to DNA bonds does not promote the development of breast cancer — the evidence is heavily against any link between living near a source of ELF-EMFs and risk of breast cancer. Exposure to microwaves from living near cell phone towers also has not been found to be associated with risk of breast cancer.
What about electric blankets?
Several studies conducted during the late 1990s and early this decade found no associations between electric blanket use and risk of breast cancer. However, one small retrospective study published in 2003 found an association among African-American women. While there do appear to be genetic differences between African Americans and other populations that influence breast cancer risk and survival, none of the known differences would explain a difference in susceptibility to household electromagnetic fields. If the risk of breast cancer is heightened for African Americans, it is likely to be heightened for most women with long-term electric blanket use. Leaving this study aside, a major 2007 study including 93,676 women reported that women using electric blankets for 20 years or more had a significantly higher risk of endometrial cancer. While warming up a bed with an electric blanket or heating pad does not carry any additional risk, using such items during sleep might increase cancer risk and we do not recommend it.