A mouse study has found the firmest animal evidence yet that cellular telephones may cause cancer, and suggests that more research needs to be done before scientists can say for certain that the portable devices are safe.
In the 18-month study, mice exposed to radio signals similar to those produced by cellular phones were twice as likely to develop cancer as their unexposed counter-parts."It's certainly the first animal evidence that suggests that radio frequencies might cause cancer under some conditions," said John Moulder, professor at the Medical College of Wisconsin in Milwaukee.
Since cellular phones first came into use, people have worried about their possible health effects. At least eight people have sued, claiming that using the phones caused brain cancer or other medical problems. But, for lack of scientific evidence, none of the lawsuits has ever made it to court.
The new study won't change that, because it doesn't come close to showing that cellular telephones are hazardous. It does raise questions that need to be investigated before the devices can be declared completely safe.
"We believe the study reported here indicates a need for further research," Michael Repacholi of the Royal Adelaide Hospital and five colleagues write in the current issue of Radiation Research.
They performed the experiment on mice that were genetically engineered to be prone to lymphoma, a cancer of the body's infection-fighting lymph system. Doing research on animals that are especially susceptible to disease is a relatively new practice, designed to increase the rates of cancers that otherwise would be too rare to detect in a practical experiment.
Of the 101 exposed mice, 43 developed lymphoma. In the unexposed group, only 22 animals developed cancer.
The odds of that happening by chance were less than 1 percent, the Australian researchers reported.
"Nobody has reported things like that in this area," said Henry Lai, a professor of bioengineering at the University of Washington in Seattle.
Lai and other researchers have found that cellular phone signals can cause DNA damage in rat brain cells. But so far other animal studies have failed to find a link between radio signals and cancer.