Radiation from cell phones hurts rats' brains. (Hold the Phone?).

A single 2-hour exposure to the microwaves emitted by some cell phones kills brain cells in rats, a group of Swedish researchers claims. If confirmed, the results would be the first to directly link cell-phone radiation to brain damage in any animal.

No such evidence exists for people. But with cell-phone use skyrocketing, some scientists recommend precautionary measures--for example, avoiding excessive gabbing on the phones.

Digital cell phones send out compressed information through microwave pulses of electromagnetic radiation. In the United States, standard phones emit 50 such pulses per second, while so-called GSM phones--which operate under the international standard called Global System for Mobile Communications--emit 217. Those pulses scatter low-level microwave radiation across the brain. To date, convincing evidence linking the phones to serious health problems, such as cancer, is lacking, says Leif G. Salford of Lund University Hospital in Sweden.

Even so, he and his colleagues are still looking for such connections. About 10 years ago, they showed that cell-phone radiation causes the protective barrier in rats' brains to leak, permitting blood proteins that are normally kept away from brain tissue to contact neurons.

Now, Salford's team reports in a forthcoming Environmental Health Perspectives that this breach of the so-called blood-brain barrier is accompanied by the death of brain cells.

Adolescent rats were exposed for 2 hours to GSM phones at one of three power levels: 0.01, 0.1, or 1 watt (W). Rats in a control group were not exposed. Cell phones typically operate at a peak output power of 0.6 W.

Examination of the animals' brain tissue 50 days later revealed that up to 2 percent of the brain cells of rats that had received cell-phone radiation exposures of 0.1 watt or greater were dead or dying. The hippocampus, cortex, and brain stem suffered the most damage. The other groups showed no significant brain-cell death.

Salford cautions that the results may not apply to real-world cell-phone use. On the other hand, he notes, "there might be negative consequences in the long run."

"It's quite intriguing," says Henry C. Lai of the University of Washington in Seattle. "The energy absorbed by the rats was really low compared to what a person gets when using a cell phone." Particularly if the effects add up over time, Lai says, regular use of cell phones could be problematic.

And it's not just the phones. In the modern, wireless office, people are increasingly exposed to a "sea of microwaves," says neuroscientist W. Ross Adey of Loma Linda University in California. "You have to ask, How much can people handle before it becomes a significant problem?" he says.

For the record, Salford himself does use a cell phone. To limit his exposure, however, he cuts calls short and distances himself from the phone with a hands-free headset.