It sounds like an urban myth the Luddites came up with to scare the madding crowd. The "cell phones cause cancer" theory has probably reached your ears by now, on its way to the 80 million Americans and more than 300 million people worldwide who own cell phones.

According to some experts, keeping in touch may indeed be hazardous to your health. Cell phone antennas, which emit relatively high doses of radio frequency (RF) radiation, are held close to the head. The main concerns from exposure to this radiation are brain cancer and other brain disorders.

Henry Lai, Ph.D., a professor of bioengineering at the University of Washington, Seattle, found that exposure to RF radiation causes DNA strand breaks in the brain cells of rats. "Strand breaks are a type of DNA damage that leads to mutation of cells. It's the same kind of mutation you see in cancer," explains Lai. "The damage can also eventually result in cell death, which may cause degenerative brain disorders such as Alzheimer's disease or Parkinson's disease."

"We don't know why RF radiation affects DNA, but we do know that the effects of exposure are cumulative," Lai adds. "Over time, the risk of developing some hazardous health effects increases. The more you talk on the phone, the greater the risk."

Battle of the experts

Not all experts agree. John Moulder, Ph.D., a radiation biologist at the Medical College of Wisconsin, says, "No single test can determine if something is a carcinogen. Lai's findings are an indicator of carcinogenic potential, but they are not conclusive. Most -- but not all -- carcinogens cause DNA damage. But not everything that causes DNA damage is a carcinogen."

As lead author of the report "Cell Phones and Cancer: What is the Evidence for a Connection?" -- published in the medical journal Radiation Research -- Moulder reviewed studies on RF radiation. He calls the link to cancer "weak to nonexistent," explaining that "the majority of the studies have indicated no significant genotoxicity. Among the studies that have reported some genotoxicity, several have failed attempts at replication."

In fact, it's not clear whether the studies have been replicated. Lai points to two other studies supporting his findings -- one by Jerry Phillips, Ph.D., and one by Luc Verschaeve, Ph.D. However, while both of these studies did indeed find DNA damage, they were not identical to Lai's; they used different types of cells (human rather than animal) and different levels of radiation. Norman Sandler, director of global strategic issues at Motorola, says Motorola commissioned a painstaking, five-year replication study in 1994 after learning about Lai's findings, but results were negative.

Sandler blames the press for what he believes is needless concern. "A lot of the media plays up contrarian findings -- there's been a huge amount of hype," he says. "Radio waves have been studied since the 1930s, and we have not seen any replicated efforts that relate to mobile phone use. Expert panels have looked at all the research and come to the same fundamental conclusion: Cellular phones pose no known hazard."

Use with caution

Despite the disagreement, Lai insists that cellular phones are a health concern. "Even if cellular phones are only a weak carcinogen, they are a serious problem because of the sheer amount of time people spend on their phone," he says.

Moulder concedes it's possible that cellular phones are a still unproven carcinogenic risk. "We try to find evidence that cell phones are a hazard. If we fail enough times, we say they are not a hazard. But what is enough? So far, no one has done a study involving large numbers of animals," he says. "While there's no evidence that cell phones are a carcinogen, absolute proof of safety doesn't exist, nor can it ever exist."

What's a prudent consumer to do?

Not even Lai suggests tossing your phone, although he does advise caution. "A cell phone is good to have, but limit your exposure by saving it for when you need it," he says. Other suggestions for reducing risk include using a headset to keep the phone transmitter away from your head and talking in open areas, where the signal is stronger and less power is needed. Devices to shield yourself from radiation, now available in Europe, may soon be available in the United States.