Magnetic fields can diminish drug action.

The low-level electromagnetic fields present in some North American homes today can diminish or wipe out a widely prescribed drug's action, at least in test tubes. Researchers have found that when exposed to such fields, the drug tamoxifen lost its ability to halt the proliferation of cancer cells grown in the laboratory. Tamoxifen is a synthetic hormone used to prevent the recurrence of breast cancer.

These findings, reported last week at a Washington, D.C., meeting sponsored by the U.S. Public Health Service, also heighten concern that these electromagnetic fields may be triggering hitherto unrecognized biological changes in people.

The new study is an extension of research that Robert P. Liburdy, a cell biologist at Lawrence Berkeley (Calif.) National Laboratory, reported on 4 years ago. At that time, he showed that while melatonin, a natural antioxidant hormone, would inhibit the growth of breast cancer cells exposed to 2 milligauss (mG) magnetic fields, its activity was essentially erased when the cells were bathed in a 12 mG field (SN: 7/3/93, p. 10).

Though the average magnetic field associated with the 60 hertz current in U.S. homes is 2 mG or lower, it can reach 12 mG in a small share of homes, such as those with unusual electric wiring. Values range as high as 1,000 mG in some occupational settings. People may also be exposed briefly to 12 mG or higher magnetic fields from electric razors and hair dryers, the sides of computer monitors, or appliances with large motors, such as refrigerators.

Liburdy and Joan D. Harland, also at the national lab, have now incubated one type of breast cancer cell treated with tamoxifen--at concentrations typical of those found in the breast cells of women taking the drug--in the presence of the same two field strengths.

Untreated cells appeared to grow equally well in each field. The growth rate of cells treated with tamoxifen fell by 40 percent in the 2 mG environment but exhibited no drop-off in the 12 mG field. Liburdy told Science News, "We've shown that you can overcome this field's suppression of tamoxifen, but to do it you've got to increase the drug dose by up to 10-fold."

Liburdy and Harland report their findings in Bioelectromagnetics (vol. 18, no. 8).

At last week's meeting, Liburdy also described follow-up research on a second type of breast cancer cell. Again, both melatonin and tamoxifen inhibited cell growth in a 2 mG environment but failed to do so under the influence of a 12 mG field.

At a Bioelectromagnetics; Society meeting earlier this year, Liburdy presented laboratory data indicating that 12 mG magnetic fields from a computer monitor, which have a slightly different wave-form than those associated with home wiring or many appliances, also erase the antiproliferative action of a hormone--in this case, melatonin.

"As basic science, this is very interesting stuff," notes Richard Stevens of the Pacific Northwest National Laboratory in Richland, Wash. Most of the new experiments were done with the most widely studied line of breast cancer cells, he notes. Moreover, "the [magnetic] field levels used are certainly relevant to humans."

While it's far too early to suggest that residential fields pose a risk to the efficacy of tamoxifen, Stevens does argue that "this study provides the rationale for wondering about and investigating such implications."

Carl F. Blackman, a biophysicist with the Environmental Protection Agency in Research Triangle Park, N.C., has recently confirmed Liburdy's finding that magnetic fields can suppress melatonin's action and is now probing the ability of low-level fields to affect the action of tamoxifen. In other experiments, he finds that electromagnetic fields can affect the development of nerve cells when concentrations of nerve growth factor are too low.

What all these studies suggest, he says, is that "in a system that is stable and unstressed, you may see no effect of these fields. But if you stimulate it or depress it a little bit"--with drug treatment or insufficient growth factors, for example--"the field may show an effect."