Cancer Risk From Cellphone Radiation Is Small, Studies Show
Do cellphones cause cancer?
Despite years of research, there is still no clear answer. But two government studies released Friday, one in rats and one in mice, suggest that if there is any risk, it is small, health officials said.
Safety questions about cellphones have drawn intense interest and debate for years as the devices have become integral to most people’s lives. Even a minute risk could harm millions of people.
These two studies on the effects of the type of radiation the phones emit, conducted over 10 years and costing $25 million, are considered the most extensive to date.
In male rats, the studies linked tumors in the heart to high exposure to radiation from the phones. But that problem did not occur in female rats, or any mice.
The rodents in the studies were exposed to radiation nine hours a day for two years, more than people experience even with a lot of cellphone use, so the results cannot be applied directly to humans, said John Bucher, a senior scientist at the National Toxicology Program, during a telephone news briefing.
美国国家毒理学计划(National Toxicology Program)的高级科学家约翰・布赫(John Bucher)在一场电话新闻发布会上说，研究中使用的这些啮齿动物连续两年每天接受九小时的辐射，超过大量使用手机的人，因此相关结果不直接适用于人类。
The results, he said, had not led him to change his own cellphone use or to urge his own family to do so. But he also noted that the heart tumors in rats ― called malignant schwannomas ― are similar to acoustic neuromas, a benign tumor in people involving the nerve that connects the ear to the brain, which some studies have linked to cellphone use.
He said that nearly 20 animals studies on this subject have been done, “with the vast majority coming up negative with respect to cancer.”
Other agencies are studying cellphone use in people and trying to determine whether it is linked to the incidence of any type of cancer, Bucher said.
The Food and Drug Administration issued a statement saying it respected the research by the toxicology program, had reviewed many other studies on cellphone safety, and had “not found sufficient evidence that there are adverse health effects in humans caused by exposures at or under the current radio-frequency exposure limits.”
美国食品药品管理局（Food and Drug Administration，简称FDA）发表了一份声明，称它尊重毒理学计划的研究，并对其他很多有关手机安全的研究进行了检查，“没有发现充分的证据表明，暴露在当前的射频暴露极限或以下会对人的健康产生不良影响”。
The statement, from Dr. Jeffrey Shuren, director of the FDA’s center for devices and radiological health, also said, “Even with frequent daily use by the vast majority of adults, we have not seen an increase in events like brain tumors.”
The Federal Communications Commission sets exposure limits for radio-frequency energy from cellphones, but relies on the FDA and other health agencies for scientific advice on determining the limits, the statement said.
声明说，美国联邦通信委员会(Federal Communications Commission)会对手机的射频能量制定辐射极限，但它依赖FDA和其他卫生机构提供科学的建议来确定这些极限。
For people who worry about the risk, health officials offer common-sense advice: Spend less time on cellphones, use a headset or speaker mode so that the phone is not pressed up against the head and avoid trying to make calls if the signal is weak. Bucher noted that the radiation emitted increases when users are in spots where the signal is poor or sporadic and the phone has to work harder to connect.
The new studies also found tumors in the brains and some other organs in the animals exposed to the radio-frequency radiation. But Bucher said those findings were “equivocal,” emphasizing that only the heart tumors provided evidence strong enough for the researchers to trust. Other possible effects need more research, he said.
Others felt that even the ambiguous findings were of concern. Joel M. Moskowitz, director of the Center for Family and Community Health at the School of Public Health, at the University of California, Berkeley, said that based on the overall results of the study, the government should reassess and strengthen the limits it imposes on how much and what types of radiation cellphones can emit.
另一些人觉得，即使是模糊的发现也值得关注。加州大学伯克利分校公共卫生学院家庭和社区健康中心(Center for Family and Community Health at the School of Public Health)主任乔尔・M・莫斯科维茨(Joel M. Moskowitz)说，根据这项研究的总体结果，政府应该重新评估和加强对手机可释放多少以及什么类型的辐射的限制。
Scientists do not know why only male rats and not females develop the heart tumors, but Bucher said one possibility is simply that the males are bigger and absorb more of the radiation.
The studies also found some DNA damage in the exposed animals, a bit of a surprise because scientists had believed that radio-frequency radiation ― unlike the ionizing radiation in X-rays ― could not harm DNA.
“We don’t feel like we understand enough about the results to be able to place a huge degree of confidence in the findings,” Bucher said.
A seemingly paradoxical finding that has also puzzled the researchers is that the rats exposed to the cellphone radiation actually lived longer than the controls. One possible explanation, Bucher said, is that the radiation may ease inflammation, and lessen the severity of a chronic kidney disorder that is common in aging rats and can kill them.
Asked if there was any chance that cellphone use could help people live longer, Bucher said: “The extrapolation to humans requires a number of steps that go beyond the realm of what we’re studying here. I don’t think that question is particularly answerable at the moment.”
The reports issued Friday were considered draft versions released for public comment and a review by outside experts on March 26-28 at the environmental health institute in Research Triangle Park, North Carolina.
周五发布的报告被认为是草稿，意在征求公众意见，并于3月26至28日在北卡罗来纳州三角研究园(Research Triangle Park)的环境卫生研究所接受外部专家的检查。