Whether or not cell phones cause brain cancer is a question that's been debated (but not answered) for years, and today the World Health Organization (WHO) stepped into the fray. A WHO committee that evaluates various potential cancer-causing agents concluded that radiofrequency electromagnetic fields, including cell phones, are "possibly carcinogenic" to people. The announcement was seized upon and published in dozens of news outlets within minutes.
The International Agency for Research on Cancer (IARC) arrived at the conclusion of possible carcinogenicity after an 8-day review of the literature by 31 experts, in Lyon, France. The classification falls in the middle of IARC's hierarchy  of risk, joining a group of more than 250 potential carcinogens that also includes  lead, engine exhaust, and occupational exposure to dry cleaning. In a sign of how tough it is to determine that something doesn't cause cancer, just one of the 900 or so agents that IARC has evaluated, caprolactam, a component of fibers and plastics, falls in the "probably not carcinogenic" category.
When it comes to cell phones, "we found some threads of evidence telling us how cancer might occur, but I think there are acknowledged gaps and uncertainties," said Jonathan Samet, chairperson of the IARC Working Group and a physician and public health expert at the University of Southern California in Los Angeles, during a press conference. The working group was particularly influenced by an international study called Interphone  that's examining whether exposure to radiofrequency electromagnetic fields from cell phones causes cancer. Last year, the Interphone study group wrote in the International Journal of Epidemiology  that it saw "no increase in risk of glioma or meningioma." It continued: "There were suggestions of an increased risk of glioma at the highest exposure level, but biases and errors" make it tough to show that the phones were the cause. "The possible effects of long-term heavy use of mobile phones require further investigation," they concluded.
IARC would like more research as well. Samet noted that at this point there are almost 5 billion cell phone subscriptions worldwide, and "we anticipate an ever larger population that is exposed for longer and longer." That said, shifting cell phones from the "possible" category to a more definitive one won't be easy. Epidemiologic studies like Interphone tend to match healthy people with those who have brain cancer and ask both to recall their cell phone use. "We know that is inherently imperfect," said Samet. And because all these studies take time to conduct, they inevitably examine older technology. Animal studies looking at the risk from radiofrequency electromagnetic fields have been mixed, both in whether they see a danger and in why that might be.
Whether IARC re-evaluates cell phone hazards, the committee says, will depend on what new research comes out.