Cellphones and new wireless technology could cause a "whole generation" of today's teenagers to go senile in the prime of their lives, new research suggests.

The study - which warns specifically against "the intense use of mobile phones by youngsters" - comes as research on the phones' effects on health is being scaled down due to industry pressure.

It is likely to galvanise concern about the almost universal exposure to microwaves in Western countries by revealing a new way in which they may seriously damage health.

Leif Salford, the professor who headed the research at Sweden's prestigious Lund University, says: "The voluntary exposure of the brain to microwaves from hand-held mobile phones" is "the largest human biological experiment ever".

People may "drown in a sea of microwaves"
And he is concerned that, as new wireless technology spreads, people may "drown in a sea of microwaves".

The study - financed by the Swedish Council for Work Life Research, and published by the American government's National Institute of Environmental Health Sciences - breaks new ground in looking at how low levels of microwaves cause proteins to leak across the blood-brain barrier.

Previous concerns about cellphones have concentrated on the possibility that the devices may heat the brain, or cause cancer. But the heating is thought to be too minor to have an effect and hundreds of cancer studies have been inconclusive.

As a result, the United States' cellphone industry has succeeded in cutting research into the phones' health effects, and the World Health Organisation is unlikely to continue its studies.

Mays Swicord, a scientific adviser to Motorola, told New Scientist magazine that governments and industry should "stop wasting money" by looking for health damage.

But Salford and his team have spent 15 years investigating a different threat. Their previous studies proved radiation could open the blood-brain barrier, allowing a protein called albumin to pass into the brain.

Their latest work goes a step further, by showing the process is linked to serious brain damage. Salford said the long-term effects were not proven, and that it was possible that the neurons would repair themselves in time.

But, he said, neurons that would normally not become "senile" until people reached their 60s may now do so when they were in their 30s.

He says he deliberately refrained from publicising his work to avoid alarm, and acknowledges that cellphones can save lives.