An international group of 23 prominent doctors and public health researchers and officials is warning that cell phone use may increase the risk of brain cancer.
One of those who signed, Dr. Ronald Herberman, the head of the University of Pittsburgh Cancer Institute, went so far as to advise his own employees to limit cell phone use.
The actions will likely add to a long-running debate on which there is little consensus among medical authorities.
"The most recent studies, which include subjects with a history of cell phone usage during the last 10 years, show a possible association between certain benign tumors ... and some brain cancers on the side the device is used," the statement reads in part.
The group behind the letter is an ad hoc group of cancer and public health experts concerned about the potential risk from cell phones. None were from Maryland-based institutions. Among those who signed the new letter are Dr. David Carpenter, director of the Institute for Health and the Environment at the University of Albany, and Herberman, director of the University of Pittsburgh Cancer Institute.
"Really at the heart of my concern is that we shouldn't wait for a definitive study to come out, but err on the side of being safe rather than sorry later," Herberman said. In the memo, sent to about 3,000 faculty and staff yesterday, he says children should use cell phones only for emergencies because their brains are still developing.
The key architect of the warning was Devra Lee Davis, head of the department of environmental oncology at the University of Pittsburgh. "The question is do you want to play Russian roulette with your brain," she said. "I don't know that cell phones are dangerous. But I don't know that they are safe." The advisory she and the others signed suggests 10 measures to limit exposure to electromagnetic radiation emitted by the cell phones, such as shortening conversations and keeping the phone away from the head. It also recommends that children not use cell phones except in emergencies.
"It's the first time such a group of public health experts have spoken out for precaution," said Louis Slesin, editor of Microwave News, a Web site that tracks electromagnetic radiation and health.
Scientists remain divided on the issue. A study published this spring in the International Jour nal of Oncology examined several previous studies, and found that there was an association between long-term cell phone use and some tumors. Several studies have found that people who have brain cancer and were heavy cell phone users tended to have tumors on the side of the head they used their phone.
But other studies have found no link between cell phone use and cancer. A 2008 University of Utah analysis looked at nine studies with thousands of brain tumor patients and concludes, "We found no overall increased risk of brain tumors among cellular phone users. The potential elevated risk of brain tumors after long-term cellular phone use awaits confirmation by future studies." Studies last year in France and Norway concluded the same thing.
Cell phones emit a small amount of electromagnetic radiation. Some researchers argue that chronic exposure to this radiation may raise cancer risk, perhaps by heating brain tissue or damaging DNA. Many researchers worry about children's exposure, because their skulls are thinner and their brains are still developing.
In January, the National Academy of Sciences issued a report calling for more research.
"There is concern about cell phone use as a risk factor for cancer. But the research is not as sophisticated as I would like," said Dan Wartenberg, chief of the division of environmental epidemiology at the Robert Wood Johnson Medical School in Piscataway, N.J. He was involved in the NAS report and also helped write the new warning.
"There's enough data that I feel it's prudent to take precaution," he said. He said he tries to keep his cell phone away from his head as much as possible, by using a headset, or putting his phone on speaker. Bluetooth technology can reduce exposure, but because it uses a transmitter in the headset, it does not eliminate the risk of brain tumors.
Slesin agreed. "All of these tumors are rare, but there are more than two billion cell phone users now. Even if it's rare, it's a huge impact from a public health point of view," he said.
The U.S. Food and Drug Administration says that "available scientific evidence does not show that any health problems are associated with using wireless phones." But the agency also notes that there is no proof that wireless phones are absolutely safe. It has called for more research.
The American Cancer Society says there is no evidence of risk. "Right now there is no association between cancer and cell phone use," said Dawn Ward, Maryland spokeswoman for the group.
CTIA-The Wireless Association, a group representing the wireless industry, says the "overwhelming majority" of research shows that wireless phones pose no health risk. The cell phone industry has helped fund a large international epidemiological study of tumors among mobile phone users. The full study has not been released.
France, Germany and the United Kingdom have recommended limiting exposure.
The Associated Press contributed to this article.