“Possibly carcinogenic” is the WHO’s third-highest rating, falling below “carcinogenic” and “probably carcinogenic” but above “not classifiable” and “probably not carcinogenic.” Other substances that the group has categorized as “possibly carcinogenic” include talcum powder, which has been possibly linked to ovarian cancer, and low-frequency magnetic fields, which are emitted by power lines and appliances and have been possibly associated with childhood leukemia.
Nonetheless, the cellphone classification marks a departure for the WHO, which previously said there were no risks from exposure to radio frequency electromagnetic fields emitted by the devices.
“The conclusion means that there could be some risk, and, therefore, we need to keep a close watch for a link between cellphones and cancer risk,” said Jonathan M. Samet of the University of Southern California, who chaired the WHO’s International Agency for Research on Cancer panel.
The classification was based primarily on two large epidemiologic studies that found an association between cellphone use and brain cancer, particularly a malignant form called glioma and a benign tumor known as acoustic neuroma.
The panel, which included 31 scientists from 14 countries, did not quantify the possible risk; nor did it estimate how much cellphone use might be safe or risky, make any recommendations about whether cellphones should be regulated more strictly, or recommend what steps consumers should take. But one panel member said users might consider common-sense precautions such as texting more instead of talking and using a headset to keep the phone farther from the head to minimize exposure.
“This is left to the individual consumer to make a decision about whether the current level of evidence is strong enough to take such precautionary measures,” Kurt Straif, who heads the IARC’s monographs program, said in a telephone briefing Tuesday.
But some experts said the conclusion should lead to immediate action, not only by consumers but also by the Food and Drug Administration and the Federal Communications Commission.
“This is the first formal acknowledgment that we may have a problem on our hands — and it could be a very big problem,” said Louis Slesin, editor of Microwave News, a trade publication. “The IARC decision, surely, is a wake-up call that people, especially children, should take sensible precautions.”
CTIA, which represents cellphone makers, dismissed the significance of the classification, noting that it was not based on new research.