EMFs in home may limit night hormone.

Two new reports suggest that women already subject to factors that decrease their secretion of the hormone melatonin may experience small further reductions in response to the electromagnetic fields (EMFs) in their homes. On the broader issue of whether EMFs affect melatonin secretion in general, the studies contradict each other.

Melatonin, which is secreted mainly at night by the brain's pineal gland, has been shown in animal studies to suppress the growth of mammary tumors. The researchers who conducted these studies ask the question, Do EMFs acting on people as they sleep lower the secretion of this hormone?

EMFs, which are ubiquitous in industrialized countries, emanate from electrical currents in power lines, wires, and appliances (SN: 8/21/93, p. 124). Although some laboratory studies have shown biological effects of EMFs (SN: 1/10/98, p. 29), studies of people exposed to elevated EMFs over short periods have failed to find any consistent effect.

A pair of reports in the Oct. 1 AMERICAN JOURNAL OF EPIDEMIOLOGY addresses whether the intensity of exposure in and around the home could affect the secretion of melatonin.

In one of the studies, a team led by Scott Davis of the Fred Hutchinson Cancer Research Center in Seattle measured urine concentrations of a breakdown product of melatonin. The researchers collected urine samples from 203 women during 6 nights and the following mornings at different times of the year. The concentration of the breakdown product, 6-sulfatoxymelatonin (6-OHMS), reflects the body's overall melatonin production. Throughout the nights of the study, meters recorded EMF intensity and ambient light in each woman's bedroom.

The strength of a woman's EMFs exposure weakly correlated inversely with her concentrations of urinary 6-OHMS, Davis' team found. That statistical relationship was strongest among women already subject to other melatonin-inhibiting factors, especially certain medications and exposure to light during the night.

In the second study, Patrick Levallois of University Laval in Quebec and his colleagues compared the nighttime urinary concentrations of 6-OHMS in about 200 women living within 150 meters of a major power line with those of a similar group of women living more than 400 m away. Although the two groups experienced different strengths of EMFs, the data revealed no difference in melatonin.

Age and obesity, like light at night and certain drugs, tend to reduce melatonin production. Levallois says his team may have found an accentuating link between EMFs intensity and melatonin production among the oldest and most obese women. However, he cautions, these correlations didn't appear in all his data analyses.

If the researchers could conduct their tests under more controlled conditions, EMFs' apparent compounding effects on melatonin-inhibited women might evaporate, says Antonio Sastre of the Midwest Research Institute in Kansas City, Mo.

The two studies seem well executed, says David E. Blask of Bassett Research Institute in Cooperstown, N.Y., "but don't exactly bear each other out." If EMFs had a strong influence, he says, "you'd see a more consistent effect."