London - Despite a recent move to classify cellphones as possibly carcinogenic, scientific evidence increasingly points away from a link between their use and brain tumours, according to a new study.
A major review of previously published research by a committee of experts from Britain, the United States and Sweden concluded there was no convincing evidence of any cancer connection.
It also found a lack of established biological mechanisms by which radio signals from cellphones might trigger tumours.
"Although there remains some uncertainty, the trend in the accumulating evidence is increasingly against the hypothesis that mobile phone use can cause brain tumours in adults," the experts wrote in the journal Environmental Health Perspectives.
The latest paper comes just two months after the World Health Organisation's (WHO's) International Agency for Research on Cancer (IARC) decided cellphone use should be classified as "possibly carcinogenic to humans".
Anthony Swerdlow of Britain's Institute of Cancer Research, who led the new review, told Reuters the two positions were not necessarily contradictory, since the IARC needed to put cellphones into a pre-defined risk category.
"We are trying to say in plain English what we believe the relationship is. They (IARC) were trying to classify the risk according to a pre-set classification system," Swerdlow said.
Other things deemed by the IARC to be possibly carcinogenic include items as diverse as lead, pickled vegetables and coffee.
Cellphone use has risen hugely since the early 1980s, with nearly 5 billion handsets in use today. Controversy about their potential link to the main types of brain tumour, glioma and meningioma, has never been far away.
The largest study to date, published last year, looked at almost 13 000 cellphone users over 10 years.
Swerdlow and colleagues analysed its results in detail but concluded it 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.
Significantly, other studies from several countries have shown no indication of increases in brain tumours up to 20 years after the introduction of cellphones and 10 years after their use became widespread, they added.
Proving an absence of association is always far harder in science than finding one, and Swerdlow said it should become much clearer over the next few years whether there was any plausible link.
"This is a really difficult issue to research," said David Spiegelhalter, Winton Professor of the Public Understanding of Risk at the University of Cambridge, who was not involved in the 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."
Swerdlow is chairperson of the International Commission on Non-Ionising Radiation Protection's Standing Committee on Epidemiology. The commission is the international body, recognised by the WHO, that constructs guidelines for exposure limits for non-ionising radiation.
Since cellphones have become such a key part of daily life - used by many for websurfing as well as talking - industry experts say a health threat is unlikely to stop people using them.