Cell phone-cancer study an enigma

A new international study of cellular phone use and brain tumors poses an enigma for epidemiologists. Though researchers found elevated risk for users who talked on average more than 30 minutes a day and had used the devices for more than a decade, moderate cell phone users actually had decreased risk compared with landline callers.

“This study did not confirm or dismiss the possible association between cell phones and brain tumors. That’s the bottom line,” says Siegal Sadetzki of Tel Aviv University’s Sackler School of Medicine.

Sadetzki and colleagues recruited 21,770 participants from 13 countries (not including the United States) as part of the Interphone study. Researchers analyzed risk for two types of brain tumors, meningiomas and gliomas, and found that only gliomas could be linked to cell phone use, and only to heavy use. Even this association was not ironclad, the researchers report online May 17 in the International Journal of Epidemiology.

Rodolfo Saracci of the National Re­search Council in Pisa, Italy, and Jonathan Samet of the University of Southern California in Los Angeles suggest that the conclusions were finessed so as not to alarm cell phone users.

“None of today’s established carcinogens, including tobacco, could have been firmly identified as increasing risk in the first 10 years or so since first exposure,” the two write in an editorial that accompanies the new paper. Tumors among the Interphone study’s participants were diagnosed between 2000 and 2004 — even though wide-scale cell phone use got under way only in the mid-1990s. Fewer than 5 percent of meningiomas and 9 percent of gliomas seen in study participants occurred among people who had used cell phones for more than 10 years.

“The question as to whether mobile phone use increases risk for brain cancers remains open,” Saracci and Samet say.

The study’s authors acknowledge that the jury is still out on cell phone safety. Until follow-up data on heavy users come in, Sadetzki recommends that cell owners adopt “the precautionary principle,” assuming that some risk might exist and limiting exposures. Tactics might include avoiding long calls, sending text messages instead of leaving voice messages and using a Bluetooth or other hands-free device to keep a mobile phone farther away from the head.