Cells proliferate in magnetic fields.

Electromagnetic fields of the strength found within a few feet of outdoor electric-power lines could trigger cells already vulnerable to cancer to behave like ones that develop into tumors, according to a new test-tube study. The new research findings contradict previous experiments on the controversial issue, which found such fields had no effect on cells in the laboratory.

Researchers at Michigan State University (MSU) in East Lansing studied the effect of magnetic fields on immature red blood cells carrying a genetic mutation that can lead to cancer. Above a threshold strength, the field prevented many of the cells from maturing, and it stimulated them to replicate over and over.

"We're almost convinced [that electro-magnetic fields] can bring about a biological effect" relevant to cancer development, says MSU's James E. Trosko. He, Hiroshi Yamasaki of the International Agency for Research on Cancer in Lyon, France, and their colleagues will publish the findings in the October ENVIRONMENTAL HEALTH PERSPECTIVES.

If the results hold up, they could elucidate whether electromagnetic fields pose a legitimate health concern, says Larry E. Anderson of Pacific Northwest National Laboratory in Richland, Wash.

Millions of people live with cells carrying genetic mutations that could lead to cancer, but the cells don't develop into tumors unless something stimulates them. The study by Trosko and his colleagues found that electromagnetic fields of 60 hertz, a low frequency, and of strengths ranging from 0.05 to 10 gauss made the mouse cells stop specializing, or differentiating, and begin nonstop proliferation.

After 4 days of exposure to such fields, about 35 percent of the mutated cells showed these effects. To understand why, Trosko says, his team plans to test whether the field induces an electric current along the inner cell membrane, disrupting signals that normally tell cells to differentiate.

Trosko notes that most people get much lower daily exposures to magnetic fields than the cells in his experiment did. However, utility workers who repair underground power lines in large cities can be exposed for hours to magnetic fields as high as 10 gauss, according to Antonio Sastre of the Midwest Research Institute in Kansas City, Mo.

In June 1999, a panel of the National Institute of Environmental Health Sciences reported that research to date has failed to establish a causal relationship between the incidence of cancer and exposure to 60-Hz electromagnetic fields (SN: 7/3/99, p. 12). The results of Trosko and his colleagues run counter to those conclusions.

Nevertheless, Trosko says, "If I'm sitting out in the sun under a power line, I'm more concerned about getting skin cancer from UV rays than about the biological effects of [electromagnetic fields]." But, he adds, if he were working full time on power lines, he might not be so complacent.