The United States Food and Drug Administration is investigating whether mobile phones can cause cancer, after two studies have shown a link between their use and the disease.

Neither study has been published, but their preliminary results have been enough to trigger the FDA investigation.

One study, by the American Health Foundation, in New York, found that mobile phone users had double the risk of developing a certain type of brain tumour than people who did not use them.

The second study, by Integrated Laboratory Systems, in North Carolina, found that DNA in human blood cells broke down when exposed to large doses of mobile- phone radiation, possibly laying the genetic groundwork for cancer.

"We are not sure what this means," said Dr George Carlo, an epidemiologist who headed the research project from 1993 until last year. "This could be a colossal coincidence or the tip of the iceberg."

With 86 million mobile phone users in the US and 30,000 new users signing up daily, "this translates into a potentially significant public health problem", the FDA said.

In Australia, more than 7 million people regularly use mobile phones. This month, The Herald revealed that Royal North Shore Hospital had advised its staff to avoid using mobile phones if possible, or to use them with a hands-free earphone and microphone "to avoid possible concentration of radiation near vital or sensitive organs".

The executive director of the Australian Mobile Telecommunications Association, Mr Peter Russell, said the advice of the World Health Organisation was that "based on the scientific evidence available today, there are no adverse health effects for people using mobile phones today".

"There have been some studies which have shown certain aspects need more investigation," he said. But no study had been successfully replicated showing that mobile phones had any detrimental effect on health.

Very few human studies have been done on the effects of mobile phones, which have been widely available for less than 15 years. Several Australian bodies, including the National Health and Medical Research Council, are conducting research into the possible health effects of the phones' use.

The head of the radiation-biology branch of the FDA's Centre for Devices and Radiological Health, Dr Russell Owen, said the two US studies raised interesting scientific questions, "but are no cause for alarm".

The details of the FDA research program will be released later this year. .

Jean A. Hoepfel, PhD
Clinical Epidemiologist
Scientific Evidence, Inc.
Adjunct Assistant Professor
University of Texas
School of Public Health
(713) 935-0744