Two studies offer some cell-phone cautions.

An expert panel in Britain offered cell-phone safety a guarded endorsement late last week. The 12 scientists, physicians, and lay members found that, to date, the balance of evidence indicates that mobile phones don't harm health.

However, the committee did compile ample indications that cell-phone emissions can induce biological changes--the health significance of which remains open to interpretation. Therefore, the panel concluded, "it is not possible at present to say that exposure to [cell-phone] radiation, even at levels below national guidelines, is totally without potential adverse health effects."

Complaints of headaches, memory problems, and dizziness have emerged among people who use mobile phones extensively (SN: 2/12/00, p. 100).

The panel--convened by the Department of Health (DOH) and chaired by Sir William Stewart, the first director of Britain's Office of Science and Technology--concludes that data gaps remain "sufficient to justify a precautionary approach." Among the precautions it advocates: Parents should permit children to use cell phones only for calls essential to safety.

The DOH immediately pledged to act on the findings, beginning with an infusion of an additional several million dollars into cell-phone research. As part of its precautionary approach, the department also vowed to outline unresolved health and safety issues in a brochure to be distributed within months to all of Britain's cell-phone users.

Research to be published in the May 25 NATURE further fuels concerns about cell-phone impacts. It finds that the type of radiation emitted by older cell phones triggers a stress-response gene. Though the creature used in the new experiments is a small roundworm, the same gene is present in many animals, including people.

When the worms get unusually warm, tissues throughout their bodies churn out heat-shock proteins. These and other animals also produce the proteins in response to additional stressors, including metals and pesticides. In general, heat-shock proteins "prevent unwanted interactions between other proteins," such as clumping or deformation that could alter function, explains Peter Candido of the University of British Columbia in Vancouver.

His coauthor David de Pomerai of the University of Nottingham in England exposed the soil nematode Caenorhabditis elegans to microwaves at a frequency and power typical of older, analog cell phones. These devices transmit signals at higher power levels and in a different signal pattern than newer digital phones do.

Candido's team had engineered strains of the nematode to reveal production of the heat-shock protein, for instance, by fluorescing. De Pomerai's group then exposed some of the nematodes to microwaves for 18 hours while shielding another batch from the radiation. Throughout the period, the scientists slowly warmed the worms.

The nonirradiated worms began pumping out heat-shock proteins at about 27 [degrees] C. Those exposed to cell-phone frequencies responded at about 24 [degrees] C. This suggests "the [independent] effect of the microwaves was equivalent to about a 3 [degrees] temperature rise," de Pomerai says.

Though microwave energy can induce warming, de Pomerai found "no temperature difference between the exposed and control worms." When reviewers questioned whether the liquid surrounding the worms might be dissipating heat, de Pomerai used more worms. He increased the worm density 25-fold, to 50 percent of the mix by weight. Again, he found no temperature increase in the irradiated worms.

He now concludes that the heatlike stress occurred in the absence of any microwave heating.

People studying cell-phone radiation have debated for years whether exposures too weak to damage DNA or induce heating could trigger any consequences. The new study now offers "a very good indication of nonthermal effects," says Henry C. Lai of the University of Washington in Seattle.

W. Ross Adey of the University of California, Riverside also finds the study "very interesting and possibly significant." However, he is troubled by the paucity of details reported because the brief account in NATURE suggests design flaws, he says.

Yet the flaws, even if present, "would not necessarily destroy the value of the observations," he argues. "These people may have chanced upon a set of conditions" in which nonthermal effects indeed occur, he says. Certainly, he adds, researchers should probe this unusual result further--not only to confirm it and find its mechanism but also to determine whether it might signal subtle harm.