A major study conducted by the National Toxicology Program has found a slight, but significant, positive correlation between radio-frequency radiation exposure (like that given off by phones) and certain cancers in rats — though only male ones.
The two-year, peer-reviewed study involved thousands of rats, each of which received one of several carefully controlled doses of radiation daily for two years (including a control group that received no radiation at all). Two to three percent of rats exposed developed glioma in the brain, and one to six percent developed schwannoma of the heart.
Strangely enough, only male rats showed these increases — and even more puzzling, the control group rats (which received no radiation) tended to live shorter lives.
The effect is weak and it would be a mistake to prematurely extrapolate results to humans, but it also won’t do to pretend the effect doesn’t exist.
Experts are still weighing in, but the trend seems to be that the results, while far from conclusive, are definitely significant.
The National Cancer Institute told TechCrunch that it was updating its cell phone radiation fact sheet to reflect the news, but did not offer further comment. (It added only that the study existed and was under review.)
The National Institute of Health issued a statement reminding people that the research does not replace or invalidate earlier studies that didn’t find cancer links; they all add to the same corpus of knowledge on this topic:
This study in mice and rats is under review by additional experts. It is important to note that previous human, observational data collected in earlier, large-scale population-based studies have found limited evidence of an increased risk for developing cancer from cell phone use.
Christopher Portier, former head of the NTP, told Scientific American:
This is by far — far and away — the most carefully done cell phone bioassay, a biological assessment. There will have to be a lot of work after this to assess if it causes problems in humans, but the fact that you can do it in rats will be a big issue.
A representative for a group of scientists petitioning for stricter rules regarding radiation exposure said the study supports their mission:
This $25 million study, executed by the U.S. government, provides support for what we are stating in the ‘International EMF Scientist Appeal’ that precautionary approach should be exercised and lower electromagnetic field exposure guidelines should be set.
Kenneth Foster, bioengineering professor at the University of Pennsylvania, concurred, but also raised questions to IEEE Spectrum:
Here you have the first borderline positive result in animals. So now you have a stronger case. The results are only in male rats, the incidence numbers were very small, and there’s no clear dose response. Did the control rats not live long enough to naturally develop these tumors?
John Bucher, associate director of the NTP, described the results in a briefing as highly important, but cautioned against making more of them than the data allow:
Overall, we feel that the tumors are likely to be related to the exposures. We felt it was important to get that word out. It is very reassuring in fact that there has been no dramatic increase. It may well be that current cellphone use is safe.
The report published today on bioRxiv is only a partial one, put out because the researchers felt it worthwhile to do so after some of the data was reported on by the website Microwave News. The full paper will be published next year.