There has been concern over the potential carcinogenic effects of radio frequency electromagnetic fields on humans for several years, and although scientists have studied the area in depth, the evidence remains inconclusive.
The latest report, from the WHO's International Agency for Research on Cancer, has classified the radio fields in the 2B risk category – which means they are possibly carcinogenic, based on an increased risk of glioma, a malignant type of brain cancer.
With an estimated five billion mobile handsets in the world, the WHO is taking no chances and said it had sifted through a mountain of evidence from various studies before reaching its conclusion.
The working group said it did not quantitate the risk, but claimed “one study of past cell phone use (up to 2004) showed a 40% increased risk for gliomas in the highest category of heavy users, who used mobile for 30 minutes a day over a ten-year period”.
However, the group stressed it lacked solid evidence for any other kinds of cancer, and would continue its research.
"The evidence, while still accumulating, is strong enough to support a conclusion and the 2B classification,” said Jonathan Samet, chairman of the working group behind the study.
“The conclusion means that there could be some risk, and therefore we need to keep a close watch for a link between cell phones and cancer risk."
To put the 2B classification in context, mobile phones rank alongside coffee and carpentry and joinery as risks, and independent experts have played down the gravity of the WHO's findings.
"So far, the published studies do not show that mobile phones could increase the risk of cancer," said Cancer Research on its Science Update blog.
"This conclusion is backed up by the lack of a solid biological mechanism, and the fact that brain cancer rates are not going up significantly. However, all of the studies so far have weaknesses, which make it impossible to entirely rule out a risk."
This article originally appeared at pcpro.co.uk