According to Park, these microwaves aren't nearly powerful enough to break apart DNA, which is how known threats such as UV rays and X-rays cause cancer. As long as a person doesn't absorb enough microwaves to actually cook themselves, he says, the energy would be far too feeble to do any damage.
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Lab studies have shown that rats and other animals can live quite happily in EMFs much stronger than any plugged-in, BlackBerry-toting human would ever experience. But such studies offer no comfort to Carpenter. "We're not concerned about the health of rats," he says. "We're concerned about the health of people."
Carpenter agrees that low-level EMFs aren't nearly powerful enough to directly break apart DNA. But he points out that many cancers are still poorly understood, and he strongly believes that low-level EMFs have enough power to cause mischief. "The evidence that some cells respond to electrical fields is overwhelming," he says. "Anybody who knows anything about biology knows that they can have an effect."
One possible scenario, according to Carpenter, is that low-level EMFs can encourage production of free radicals, destructive molecules that can damage cells and perhaps even break up DNA. It's already well-known that ultraviolet rays can create free radicals, and some laboratory studies suggest that low-level EMFs can do the same.
In 2008, Ashok Agarwal, director of research at the Center for Reproductive Medicine at the Cleveland Clinic, published a study showing that men who spent a lot of time on cellphones tended to have unusually low sperm counts. He has also conducted laboratory studies showing that cellphone radiation could damage sperm in test tubes.
Agarwal says there's not enough evidence to tell men with fertility problems to give up their cellphones, although he personally believes that spending 10 hours a day on the phone isn't exactly a fertility-friendly lifestyle, radiation or no. Men who want to protect themselves can simply put their cellphones in their shirt or jacket pocket instead of their pants pocket, he says. "It's a little inconvenient, but it might be safer."
Rees has her own defense strategy. She shuns cellphones and spends as much time as she can in low-EMF areas. "I like to spend time in the mountains and by the sea," she says. Getting far away from power lines and Wi-Fi hot spots feels relaxing and rejuvenating, she says.
Undoubtedly, that's true. But does her health -- or anyone's -- have anything to do with EMFs? That argument isn't over.