Another way EMFs might harm tissues.

Though several studies have linked exposure to electromagnetic fields (EMFs) with an increased risk of developing any of several cancers, researchers have been hard-pressed to identify biologically plausible explanations for such associations. One possible mechanism gaining currency is the apparent ability of EMFs to modulate secretion of a brain hormone -- melatonin -- that regulates estrogen synthesis (SN: 7/3/93, p.10). In the Feb. 4 SCIENCE, Stanford University chemists describe witnessing another possible mechanism -- the ability of weak EMFs to disrupt lipid membranes such as those that serve as the gatekeepers for chemicals seeking to enter or exit cells.

Harden M. McConnell and his coworkers created a simple membrane by floating molecules of fat-like lipids on the surface of water in a covered dish. Inside a glass pipette mounted vertically through the center of the surface film, the researchers inserted a wire that was connected to a power source. By running a current through the wire, they generated a weak electric-field gradient across the film's surface.

Under temperature and pressure conditions that might exist in living cells, they showed that even weak electric fields could induce a phase separation in the film -- essentially a breakdown in the structure of this model barrier. If similar disruptions occur in real cells, McConnell says, they might alter receptors on a membrane surface and in so doing trigger an inappropriate cellular response.

The February HEALTH PHYSICS reviews many of the cellular, behavioral, immune system, and membrane effects seen in other EMF studies. "No mechanism has been identified that completely explains the link between EMFs and bioeffects," write William R. Hendee of the Medical College of Wisconsin in Milwaukee and John C. Boteler of SciCon Associates in Flagstaff, Ariz. However, they note, because most EMF effects appear to relate to a combination of field intensity and frequency, "less is not necessarily better." Argue the authors: Until the mechanisms and their relationship to cancer can be clarified, "prudent avoidance" of EMFs makes sense.