The announcement comes from the International Agency for Research on Cancer (IARC). Like the World Health Organization, the American Cancer Society relies on IARC for evaluation of cancer risks.
"After reviewing all the evidence available, the IARC working group classified radiofrequency electromagnetic fields as possibly carcinogenic to humans," panel chairman Jonathan Samet, MD, chair of preventive medicine at the USC Keck School of Medicine, said at a news teleconference. "We reached this conclusion based on a review of human evidence showing increased risk of glioma, a malignant type of brain cancer, in association with wireless phone use."
In finding cell phones to be "possibly carcinogenic," the IARC means that heavy cell phone use might -- or might not -- cause a specific form of brain cancer called glioma. The finding means that research is urgently needed to find out whether cell phones actually cause cancer, and how they might do it.
The IARC estimates that some 5 billion people worldwide have mobile phones. Lifetime exposure to the magnetic fields created by the phones -- particularly when they are held tightly against the head -- rapidly is increasing.
Children are at particular risk, not only because their skulls are thinner but also because their lifetime exposure to cell phones likely will be greater than the exposure of current adults.
Putting Possible Cancer Risk in Perspective
It's important to put the possible risk into context. Kurt Straif, MD, PhD, MPH, head of the IARC Monographs Program, notes that the IARC currently lists some 240 agents as "possibly carcinogenic," including dry cleaning fluid and some commonly used pesticides.
While the IARC doesn't make recommendations to consumers, Straif noted that there are precautions people can take.
"Some of the highest exposures come from using mobile phones for voice calls. If you text, or use hands-free devices, you lower exposure by at least [10-fold]," Straif said at the news conference. "So this is left to consumers to consider whether this level of evidence is enough for them to take such precautions."
Otis W. Brawley, MD, chief medical officer for the American Cancer Society, notes that the IARC is a highly credible group. But Brawley echoes Straif's advice: People who are worried can reduce their risk.
"On the other hand, if someone is of the opinion that the absence of strong scientific evidence on the harms of cell phone use is reassuring, they may take different actions, and it would be hard to criticize that," Brawley says in a news release.
John Walls, vice president for public affairs at CTIA, the trade group representing the wireless communications industry, notes that the IARC findings do not mean cell phones cause cancer -- and that the limited evidence on which the findings are based are far from conclusive.
"Based on previous assessments of the scientific evidence, the Federal Communications Commission has concluded that '[t]here’s no scientific evidence that proves that wireless phone usage can lead to cancer.' The Food and Drug Administration has also stated that '[t]he weight of scientific evidence has not linked cell phones with any health problems,'" Walls notes in a news release.
Samet and colleagues will publish a summary of their findings in the July 1 issue of The Lancet, which is still in press.