Does cell phone radiation cause cancer? There’s no firm answer to that question, but after days of peer review sessions over two National Toxicology Program (NTP) draft reports, experts believe there is “clear evidence” phone radiation led to heart cancer in rats.

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NTP’s draft reports came out earlier in 2018; at that time a National Institute of Environmental Health Sciences (NIEHS) news release said, “High exposure to radiofrequency radiation (RFR) in rodents resulted in tumors in tissues surrounding nerves in the hearts of male rats, but not female rats or any mice,” and noted the expert review to take place over March 26 to 28. Quartz said all the results were then described as equivocal — the scientists didn’t think their information was clear enough to pin down if radiation led to the health effects.

Related: Images Show How Much Cell Phone Radiation We Bathe in Every Day

Peer reviewers, including toxicologists, engineers, biostaticians, and brain and heart pathologists, scrutinized the data and upgraded multiple conclusions to “some evidence” or “clear evidence,” Quartz said.

NTP exposed mice and rats to varying levels of RFR for as long as two years. NIEHS said, “The exposure levels used in the studies were equal to and higher than the highest level permitted for local tissue exposure in cell phone emissions today. Cell phones typically emit lower levels of RFR than the maximum level allowed.”

We certainly can’t say for sure at this point that cell phone radiation causes cancer in humans. NTP senior scientist John Bucher said in NIEHS’ February news release, “The levels and duration of exposure to RFR were much greater than what people experience with even the highest level of cell phone use, and exposed the rodents’ whole bodies. So, these findings should not be directly extrapolated to human cell phone usage. We note, however, that the tumors we saw in these studies are similar to tumors previously reported in some studies of frequent cell phone users.”

+ National Toxicology Program Draft Reports

+ National Institute of Environmental Health Sciences

Via Quartz

Images via Depositphotos, Hassan OUAJBIR on Unsplash and Matthew Kane on Unsplash