A new government study found cancerous tumors in the brain and heart of male rats that received high exposure to radiation similar to that emitted by mobile phones.

Although the tumors appeared in low rates, the partial results of the two-year study by the U.S. National Toxicology Program is a major finding, reviving the long debate over the health effects of radio frequency radiation on humans.

The study partially supports a 2011 finding from the World Health Organization, which led the group to classify the radio frequencies regularly emitted by mobile phones in the same group as other potentially cancer-causing substances.

The new study’s conclusion, which was posted Thursday night, is more measured. It noted that pre-cancerous legions on the heart and brain of male rats studied are “considered likely” the result of whole body exposure to cellphone radio frequencies. There were limited instances found in female rats, but the report concluded that they were not “biologically significant.”

John Bucher, who helps like the U.S. National Toxicology Program, said it is still unclear how the results translate to humans.

“This may have relevance, it may have no relevance,” he said, adding that the study has not changed the way he uses a cellphone.

The rats were exposed to frequency bands at the 900 MHz zone, which is primarily used in the United States. The rats were exposed to cycles of the radiation for 10 minutes on and 10 minutes off — which equated to about 9 hours of exposure every day.

A more comprehensive study on the possible toxicity and cancer-causing effects of radiation associated with cellphones is due out in 2017. But the authors’ of the study released the partial findings because of the wide public and media interest in the issue.

“Given the widespread global usage of mobile communications among users of all ages, even a very small increase in the incidence of disease resulting from exposure to RFR could have broad implications for public health,” according to the report.

The report has the potential to heat up a simmering debate at the federal government and in major cities about the issue. The wireless industry has successfully sued to block a number of cities from forcing retail stores that sell mobile phones from warning customers about radiation dangers.

The Federal Communications Commission has been briefed on the study and said it would continue to follow “all recommendations from federal health and safety experts including whether the FCC should modify its current policies and RF exposure limits.”

The official position of the FCC is that it does not know if there is risk from exposure to radio frequencies emitted by mobile phones and that research is ongoing. The FCC notes there is currently no scientific evidence that mobile phone usage can lead to cancer, headaches, dizziness or memory loss.

If there are risks, the FCC predicts they are small. The amount of radio frequency to be absorbed into the head of a person using a mobile phone is at called the Specific Absorption Rate. The FCC sets that limit at 1.6 watts per kilogram.

The Government Accountability Office in 2012 found that those limits might not reflect the latest research and may not address exposure limits to the body, for example, when someone carries their phone in their pocket while using headphones.

via Talk of Juba