WHO classification sparks debate over cell phone safety.

F ar from settling the question of whether cell phones cause cancer, the latest pronouncement by the World Health Organization that cell phones could “possibly” be carcinogenic has left a wake of confusion and consternation. In July ’ s The Lancet Oncology , the WHO ’ s International Agency for Research on Cancer (IARC) announced that it had classifi ed radiofrequency (RF) electromagnetic fi elds — such as those that wireless phones emit — as “possibly carcinogenic to humans” based on an increased risk of glioma and acoustic neuroma. The move came barely a year after the huge Interphone study found no increased risk of cancer from more than 10 years of cell phone use. But the Interphone results, published here in the Journal ( see J. Natl. Cancer Inst. 2010; 102:13), suggested there might be some risk for people with the heaviest use. The National Cancer Institute, the American Cancer Society, and other organizations were at pains to update their online information and reassure worried consumers that the WHO action was not based on any clinically meaningful new evidence but merely on an evaluation of the existing literature. Experts repeated the familiar mantra “more research is needed,” even as newspaper headlines warned of the potential risk. Some observers missed the small print. The IARC ’ s 2B classifi cation — “possibly carcinogenic to humans” — was based only on “limited evidence of carcinogenicity.” According to IARC, that means: “A positive association has been observed between exposure to the agent and cancer for which a causal interpretation is considered . . . to be credible, but chance, bias, or confounding could not be ruled out with reasonable confi dence.” As Jonathan Samet, M.D. , overall chair of the IARC working group and chair of preventive medicine at the University of Southern California, told a press conference in Lyon, France, on May 31, the classifi cation means “there could be some risk, and therefore we need to keep a close watch for a link between cell phones and cancer risk.”