A report published by the National Toxicology Program found a “modest” link between some radio waves from some cellphones and cancer rates in male rats, according to The New York Times. The $30 million study, which involved 3,000 rodents, has been in progress since the Clinton administration. While concerning, the radiation exposure levels and length of use was much longer than that of any normal person using a cellphone or smartphone today researchers say. The rats were exposed to radiation for nine hours a day for two years, starting from before birth until age 2. Of these rats, 2 to 3 percent of male rats developed malignant gliomas—a terminal brain cancer. Experts, however, don’t see a comparable rise in malignant gliomas among humans. Still, researchers say, it’s a sign that the lower the exposure of radiation between human and phone, the better.