New research aiming to incorporate the best data from previous studies indicates that cellphones really do increase the risk of brain cancer. Independent studies follow-up over a long period suggest the risk is doublerd for heavy phone users.
"We conclude that the current standard of exposure to microwave during mobile phone use is not safe for long-term exposure and needs to be revised," say the authors, led by RB Dubey of India's Apeejay College of Engineering.
There have only ever been 11 long-term studies into the risks of mobile phone use, and these have shown mixed results. Earlier this year, the ten-year Interphone study concluded that only for very high users was the risk of brain tumors possibly increased; however other studies, including work by professor Lennart Hardell, have found that there is a substantial increase in risk.
Another long-term study is currently in progress in Europe - but will take 30 years to reach any conclusions.
Dubey's team integrated data from both the Interphone and Hardell studies to reach their conclusions. They say: "Long-term cell phone usage can approximately double the risk of developing a glioma or acoustic neuroma in the more exposed brain hemisphere," - that is, on the side the user typically holds the phone.
While the full research hasn't yet been published, so Dubey's figures aren't yet available, the incidence of brain cancer in the US is generally given as 15 to 20 cases per 100,000 people.
It's not exactly clear how microwave radiation from cell phones might increase brain cancer risk. However, studies have shown that the cell signal is absorbed up to two inches in the adult skull - and much more deeply in children.
The researchers call for government action to revise standards for microwave exposure.
"The precautionary principle clearly applies in this case, since the problem is possible but not certain and low cost ameliorating actions are easily implemented by industry," they say. "With over three billion people using cell phones and with children among the heaviest users, it is time for governments to mandate precautionary measures to protect their citizens."
Some are already moving in this direction: concerned about the issue, San Francisco's Board of Supervisors recently voted overwhelmingly in favour of a law requiring retailers to display the amount of radiation emitted by cellphones.
The full report will appear in the Journal of Computer Assisted Tomography.