According to Reuters, a major review of published research by a committee of international experts led by Britain's Institute of Cancer Research concludes that "the accumulating evidence is increasingly against the hypothesis that cell phone use can cause brain tumors in adults." The study also pointed out the lack of any established biological mechanisms by which the radio waves produced by cell phones might trigger tumors.
This study comes shortly after a highly publicized move by the World Health Organization (WHO) to classify cell phones as "possibly carcinogenic to humans". The study leaders point out that the WHO was required to place cell phones into a predefined risk classification system, which overemphasizes the uncertainty of the cancer risk. Other things classified as "possibly carcinogenic" include lead, pickled vegetables and coffee.
In reviewing the existing research, the study leaders determined that the largest study to date, which looked at almost 13,000 mobile phone users over 10 years, gave no clear answer and had several methodological problems, since it was based on interviews and asked subjects to recall phone use going back several years.
Research from countries that followed brain tumor rates after cell phones were introduced showed no increases after their use became widespread.
David Spiegelhalter, Winton Professor of the Public Understanding of Risk at the University of Cambridge, who was not involved in the study, points out that this is a very difficult issue to study, "But even given the limitations of the evidence, this report is clear that any risk appears to be so small that it is very hard to detect — even in the masses of people now using mobile phones."