After reviewing dozens of published studies on the health risks of exposure to radiation emitted by cell phones, a working group of the World Health Organization International Agency for Research on Cancer (IARC) has classified cell phone emissions as “possibly carcinogenic to humans.” Announced on Tuesday, the IARC’s pronouncement caps a week-long meeting of 31 experts from 14 nations who assessed the results of studies involving both humans and animals, as well as research conducted under the auspices of the 13-nation Interphone project. Concluded in May of 2010, the Interphone study found no increase in the risk of two brain cancers— glioma and meningloma—with mobile phone use. The study stated, however, that there were suggestions of increased glioma risk at the highest levels of exposure. Results of a U.S. National Institutes of Health study earlier this year cited an increase in brain activity associated with mobile phone use, although it did not find evidence of a cancer link or other adverse health effects. In classifying cell phones as “possibly carcinogenic,” the IARC is categorizing cell phones with agents “for which there is limited evidence of carcinogenicity in humans and less than sufficient evidence of carcinogenicity in experimental animals.” Other agents that share the IARC’s “possibly carcinogenic” category include the pesticide DDT and exhaust from gasoline engines. Commenting on the working group’s conclusions, an IARC spokesman said, “we found some threads of evidence telling us how cancers might occur, but there were acknowledged gaps and uncertainties.” An official of wireless association CTIA, meanwhile, emphasized that the IARC’s classification “does not mean cell phones cause cancer,” noting that the IARC “has given the same scores to, for example, picked vegetables and coffee.”