In April this year, Siddhartha Mukherjee, an oncologist who was awarded a Pulitzer Prize for his book "Emperor of All Maladies: A Biography of Cancer," debunked claims that the electromagnetic radiation from mobile phones can cause cancer.

Mukherjee said that if mobile phones were indeed causing cancer, the prevalence of the disease would have increased several times given the growth of mobile phone usage over the past years. Findings of a new study conducted by researchers in France, however, may prove Mukherjee wrong.

The new study published in the British journal Occupational and Environmental Medicine on May 9, shows that people who use their cellphone for 15 hours or more per month on average are up to three times more at risk of developing brain tumor than individuals who seldom use their cellphones.

For the study "Mobile phone use and brain tumours in the CERENAT case-control study," Isabelle Baldi, from the University of Bordeaux in France, and her colleagues compared 253 individuals with glioma and 194 individuals with meningioma with a group of healthy people to analyze a possible link between mobile phone use and brain tumors.

The researchers found that the risks for gliomas and meningiomas rise with increased use of cellphone particularly in individuals whose jobs involve heavy use of phone such as those in the sales industry. The average duration of phone use in the study was five years.

The researchers said that the data they have gathered support previous findings on the possible link between brain tumors and heavy use of mobile phones. Nonetheless, they observed an anomaly in the study that was in contrast with findings of previous research. They found that the cancer occurred on the side of the patients' brain that is opposite to the where the phone is often used.

"These additional data support previous findings concerning a possible association between heavy mobile phone use and brain tumours," Baldi and her colleagues wrote.

Still, the findings may not yet put an end to the controversy regarding the cancer-causing effects of radiations from mobile phones. The researchers said that it can be difficult to find an accurate association between cellphone use and cancer because this would require filtering out other behaviors linked with cancer such as smoking.

"It is difficult to define a level of risk, if any, especially as mobile phone technology is constantly evolving," the researchers said. "Studies taking account of these recent developments and allowing the observation of potential long-term effects will be needed."