Laboratory animals revealed an increased cancer risk

Previously a number of studies on laboratory animals looked at the possibility of radio frequency energy causing cancer, and most found no causal link. One exception was a 1997 study that exposed a strain of mice prone to lymphoma to daily doses of radio frequency signals similar to those transmitted by GSM-type handsets during 18 months. The researchers reported that the number of new lymphoma cases among exposed mice was twice that of non-exposed mice.

Other researchers who carried out a similar experiment in 2002 found no significant effect on the number of new lymphoma cases in mice. One difference between the two experiments was the mode of exposure. In the 2002 study the exposure was one hour a day five days a week, whereas in the 1997 study it was 30 minutes twice a day, seven days a week.

Other studies have tested whether exposure to radio frequency fields alone could trigger any type of cancer in normal or genetically predisposed animals. Other studies have investigated whether exposure to RF fields could enhance the development of tumours triggered by cancer-causing chemicals, X-rays or UV radiation. No significant increase in the number of tumour cases has been reported among exposed laboratory animals, but most of these studies used relatively low exposure