If you spend a lot of time on your mobile phone, you'll be happy to learn that your habit isn't hazardous to your health, according to a new government safety report.
The findings, released Friday by the National Toxicology Program, reaffirm the agency's previous research.
"The reports don't go much further than what we had reported earlier, and I have not changed the way I use a cellphone," NTP senior scientist John Bucher said in a briefing.
The new evidence is based on experiments with rats and mice that were exposed to radiofrequency radiation for as long as two years. The rodents were bathed in the radiation for 10 minutes at a time, followed by a 10-minute break, for about nine hours a day.
The lowest level of radiation for rats was 1.5 watts per kilogram of body weight, which was equivalent to the maximum amount of exposure allowed for humans, the NTP said. At the high end, rats received 6 watts of radiation per kilogram of body weight.
For mice, exposures ranged from 2.5 to 10 watts per kilogram of body weight.
On the whole, the mice weathered the radiation just fine, with "little indication of health problems," the NTP said in a statement.
The rats didn't fare quite so well.
Both male and female rats exposed to radiation were more likely to experience cardiomyopathy, a disease that causes damage to heart tissue.
In addition, male rats exposed to the highest levels of radiation had an increased incidence of malignant tumors in the tissue that covers nerves in the heart. These nerve sheath tumors, called schwannomas, were not seen in female rats.