SUSAN DENTZER: More than 90 million Americans and at least half a billion people worldwide, depend on cellular phones to stay in close touch. But as cell phone use has grown, so have concerns that the radio frequency signals that carry sound from phone to phone could have adverse health effects.
There have been fears that signals emitted from the antennas of hand-held cell phones could cause brain cancer, or that the signals could cause genetic damage in human blood.
For example, several high- profile lawsuits have been filed alleging damage from cell phones. Last summer, a Maryland neurologist asked for $800 million in damages against Motorola and Verizon, charging that his cell phone use had caused brain cancer. That case is now pending. And in a recent book that garnered media attention, one researcher, Dr. George Carlo, claimed that he had found evidence linking cell phone use to both brain cancer and genetic damage to blood cells.
But in contrast to some users' fears, and to concerns raised by Carlo and a handful of other researchers, two new studies suggest no statistical link between cell phone use and brain cancer.
SUSAN DENTZER: The first, published last week in the "Journal of the American Medical Association," compared a group of 469 men and women with brain cancer with a slightly smaller group of people without the disease. 66 of the cancer patients reported using handheld cellular telephones for an average of just under three years, as did 76 of the patients who were well. A statistical analysis showed no connection between brain cancer and cell phone use, says Joshua Muscat, the lead researcher in the study.
JOSHUA MUSCAT, American Health Foundation: We found that regardless of how frequently the phones were used per month or how many years that the phones were used, there wasn't any relationship with the developments of brain cancer.
SUSAN DENTZER: Not only was there no apparent link to cancer, there was also no indication that cancers appeared more often on the side of the head where patients tended to use the phones -- that seemed to strengthen the case that the phones' radio frequency signals weren't harmful.
JOSHUA MUSCAT: Radio frequency waves are low-energy waves. They are not like x-rays, which have been shown to cause genetic damage. They don't produce any harmful physiological effects that we know of.
SUSAN DENTZER: A second, even larger study by researchers at the National Cancer Institute yielded similar results. In this one, to be published in January in the "New England Journal of Medicine," examined the cases of 782 hospitalized patients with various forms of brain cancer; they compared them to 799 other hospital patients with no brain cancer. Of the two groups, 311 of the brain cancer patients had used cellular phones, versus 359 of those who were cancer-free. Once again, researchers found no evidence of increased risk of cancer from cell phone use. Despite the new studies' seemingly good news, even the researchers who conducted them warned that it was far too soon to grant cell phone use a completely clean bill of health.
JOSHUA MUSCAT: Cell phones have only been around for a few years and so most people who have used cell phones have used them on average for about two or three years. We need to keep in mind that there might be unknown effects associated with longer usage, and so that needs to be studied in the future.
SUSAN DENTZER: Meanwhile, cell phone producers have started to disclose just how much radiation their phones emit. These are stated in terms of so- called "SARs," or specific absorption rates, that indicate the number of watts of radiation the body absorbs for each kilogram of weight. Although no one really knows what level is safe, for now the Federal Communications Commission has set a maximum SAR of 1.6 for cell phones. You can determine your phone's rating by locating its FCC ID number on the back, and then looking up the matching SAR on the FCC Internet page.
People worried about cell phone use can also take precautions. One is to avoid using a phone inside a building or wherever the signal is weak, since this requires the phone to emit more radiation. Cell phone users can also get external antennas for their cars, or use portable, hands-free headsets like this one with the phone held as far as possible away from the body. And some experts say it makes sense for now to avoid long cell phone chats-- at least until more cell phone safety research produces more definitive results in the future.