While not stating that there is definitely or even probably a link between cell phones and cancer, the World Health Organization has significantly changed its story about the health effects of your phone.

In the past, the WHO has said unequivocally that there were “no risks from exposure to radio frequency electromagnetic fields emitted by the devices.”

Now, they’re assigning them to their third-highest rating on the carcinogen scale. This puts cell phones in the same category as lead, chloroform, and the widely-banned pesticide DDT.

Specifically, the study found “limited evidence” linking cell phone use to two types of brain tumors; there was “inadequate evidence to draw conclusions for other cancers,” according to the report (PDF).

Studies on cell phone use are difficult for many reasons. One is that, as of 2010, approximately 5 billion people, close to three-quarters of the world’s population, were cell phone subscribers. That makes it hard to differentiate cancer rates among those who do and don’t use phones. One controversial study last year was based only on the recollections of people who already had cancer about how much they used their cell phones over ten years ago. (That study found “no clear link” between cell phones and cancer.)

A non-scientific user poll conducted by the Washington Post suggests that only 6% of readers who hear about the study say they plan to “discontinue use” of their cell phone, compared to 30% who say it won’t change their cell phone use.

That probably makes sense, according to Matthew Herper at Forbes.com:

“The study the WHO is citing only showed the 40% increase in the 10% of people who used cellphones most. I don’t know how many people in the U.S. would now fall into this group, but we’d be talking about maybe hundreds of cases spread out over the whole U.S. population.”

Otis Brawley, chief medical officer of the American Cancer Society, recommends using a headset: “If there is a risk, most of it goes away with a wireless earpiece.”

Brawley also noted, “Cell phones may cause brain tumors but they kill far more people through automobile accidents.”

Good point.

CNN reported more on this yesterday: