Talking on the cellphone may possibly lead to a malignant form of brain cancer, the World Health Organization has said. A study done by an arm of the world body has classified radiation coming out of cellphones alongside gasoline engine exhaust, lead and DDT as "possibly carcinogenic to humans".

The International Agency for Research on Cancer, which is under WHO, however, said there wasn't enough evidence yet to conclusively link mobile phone use with cancer.

"The WHO/IARC has classified radiofrequency electromagnetic fields as possibly carcinogenic to humans (group 2B), based on an increased risk for glioma, a malignant type of brain cancer, associated with wireless phone use," it said.

"This does not mean the link has been firmly established," said IARC's chief of the monograph programme, Dr Kurt Straif. "But there is reason for concern."

The group, consisting of 31 scientists from 14 countries, examined "hundreds of epidemiological studies" on cellphone use to see what the long-term health effects might be after exposure to radio frequency electromagnetic fields.

The International Agency for Research on Cancer's monograph programme, which consists of 31 scientists, said that they reviewed the data from hundreds of studies on effects of cellphone radiation, and believe mobile phone usage is limited to a risk of glioma and acoustis neuroma (a benign but life-threatening tumor).

They did not have enough data to conclude that it could cause any other forms of cancer.

"After going through hundreds of studies, we concluded that there is just a possibility of a link between high cellphone use and brain cancer, not a certainty. We also don't know how much radiation exposure can be termed harmful," Straif said. One of the studies the researchers looked at said that those who had spent 1,600 hours of active call time over 10 years - around 30 minutes a day - could be at highest risk.

"But, what was considered a long talk time a few years back is considered low usage now. So there is no clear picture," he added. According to Dr Straif, it is now left to governments and organizations like WHO to come out with recommendations based on evidence provided by IARC.