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The only finding of two new government studies on the safety of mobile phones is that there is only a small boost in an unusual type of heart tumor in male rats exposed to super-high doses of radiation. Other than that, the two bodies of research concluded that cell phones are safe for human use.
The results would hopefully put an end to speculations that too much use of cell phones causes cancer or brain tumors, KSAT reported. Among female rats, there were no significant problems even if the rodents were also exposed to high doses of mobile phone radiation.
Does Not Reflect Real-Life Use
However, the study admitted that it does not reflect real-life mobile phone use. Nevertheless, the findings of a rare nerve-tissue tumor that was discovered in the hearts of male mice does not translate directly into a concern for humans, John Bucher, the lead author from the National Institute of Environmental Health Sciences, said.
The NIEHS made the $25-million study on the request of the US Food and Drug Administration. Following the release of the results, Dr. Jeffrey Shuren, the radiation health chief of FDA, said that the current safety limits for mobile phones are acceptable for protecting public health.
For nine hours a day up to two years, the rats were bombarded with radiation levels so high but humans would experience it only briefly when a phone with weak signal uses more energy searching for a stronger signal, Bucher said. Interestingly, the rodents exposed to radiation lived longer than rats that belonged to the control group which was not exposed to radiation from mobile phones.
The exposure levels ranged from 1.5 to 6 watts per kilogram in rats and 2.5 to 10 watts per kilograms in mice. The animals, which were housed in special chambers, were given increments of 10-minutes' on-and-off exposure, according to NIHS.
The studies used 2G and 3G frequencies and modulations that are still used in voice calls and texting in the US. However, more recent 4G, 4G-LTE, and 5G networks for video streaming and downloading attachments are now using different mobile phone signal frequencies and modulation compared to the ones used in the study.
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Bucher attributed it to chance or the radiation possibly reducing inflammation in the rodents that decreased the risk of disease in the mice. The preliminary results of the toxicology program released in 2016 showed a hint of increased brain tumors in male mice. However, the final report had different findings.
While the new study found equivocal evidence for hikes in DNA damage, brain tumors, and a few other cancers, it was unclear if it was related to the mobile phones. Bucher said there was evidence of DNA damage seen in some tissues of some animals, but the researchers felt they did not have evidence to comment on its biological significance.
Not a Huge Effect
Leike Kjeifets, an epidemiology professor at the University of California, Los Angeles, said it was surprising that the rats experienced a variety of other effects even if the radiation the animal was exposed to was not high enough levels to be considered significant and possibly linked. The former head of radiation studies for the World Health Organization said that there is some concern about so much activity going on, although she added that definitely, it is not like the sky is falling.
Critics of the two new government studies, such as David Carpenter, the head of environmental health at the State University of New York, said the research was not large enough to discover some rare problems. But Carpenter said that the claim of equivocal findings of brain tumors cannot be set aside. He acknowledged that the danger is nowhere near as bad as that from cigarettes, but Carpenter insisted that there is a real hazard from excessive use of mobile phones.
Previous studies, such as the one which the International Agency for Research on Cancer conducted in 2011, said that cellphones are possible cancer-causing. But among the largest studies, an analysis in 13 nations done in 2010 found little or no risk of brain tumors. The possible link in the heaviest users the authors of the study was even found not to be conclusive. In the latest update in 2007, a large research in Denmark which linked phone bills to a cancer registry did not find any risk from over 13 years of mobile phone use.
Shuren said that based on FDA’s ongoing evaluation of the issue and taking into account all the available scientific evidence the regulator has received, there is no sufficient evidence of adverse health effects in people caused by exposure at or under the current radiofrequency exposure limits. He added that despite the frequent daily use of the cell phone by a majority of adults, the FDA had not seen an increase in brain tumors. Shuren said that based on the current information available, the current safety limits for mobile phones are acceptable.
[메디컬리포트=Vittorio Hernandez 기자]