EMFs are invisible areas of energy that result from the flow of electric current. Common sources of EMFs include power lines, electrical wiring, and appliances. Although electric and magnetic fields are related, they have different properties. The strength of both electric and magnetic fields decreases rapidly with increased distance from the source. Unlike electric fields that can be shielded by objects, magnetic fields cannot. Because of this, the ability of magnetic fields to impact human health adversely is considered more likely.
The scientific community is investigating a causal link between magnetic fields and breast cancer. A widely held theory is that magnetic fields increase breast cancer risk by affecting the bodyís melatonin levels. Melatonin is a hormone produced by the pineal gland (located at the base of the brain) in response to a lack of light. Melatonin levels are typically low during the day, and increase at night, peaking between 2 and 4 a.m. Exposure to higher levels of magnetic fields is thought to suppress this normal nocturnal rise in melatonin.
Melatonin levels are believed to be inversely related to estrogen levels. For example, when melatonin levels are low, estrogen levels are believed to be high, and vice-versa. Therefore, if light-at-night or magnetic field levels suppress the normal nocturnal rise in melatonin, estrogen levels would subsequently be increased. Because increased levels of estrogen are hypothesized to increase the risk of breast cancer, this suppression of melatonin by magnetic fields possibly could increase the risk of breast cancer.