Two government studies that bombarded rats and mice with cellphone radiation found a weak link to some heart tumors, but the research does not provide any clear answers about the safety of the devices that seem like extensions of our bodies.

The lead author of the research, John Bucher, says scientists used greater radiation than typical for human cellphone use and found an increase in an unusual type of heart tumor in male rats but nothing else significant in females or any mice. The same study showed that the radiated rats somehow lived longer than the control group that was not radiated.

Bucher said the finding of rat heart tumors does not translate directly to humans. And he isn't changing his cellphone use.