Questions and Answers on the New Study Linking Cellphones and Cancer in Rats
Do cellphones cause cancer? Most health authorities do not think so, but a new federal study could reignite the controversy over this issue.
The preliminary study, released Friday, found that radiation from cellphones appears to have increased the risks that male rats developed tumors in their brains and hearts. But there are many caveats and some experts are debunking the study.
Who conducted the study? Are they credible?
The study is from the National Toxicology Program, an interagency group in the Department of Health and Human Services whose job it is to assess the possible risks of chemicals.
这项研究是美国国家毒物管理局(National Toxicology Program)做的，它是美国卫生与公众服务部(Department of Health and Human Services)的一个跨部门机构，其职责是评估化学物质的潜在风险。
How was the study done?
Rats lived in special chambers where they were exposed to different levels of radiation of the type emitted by cellphones for nine hours a day, every day. The exposure started before they were born and continued until they were about 2 years old.
What did they find?
About 2 to 3 percent of the male rats exposed to the radiation developed malignant gliomas, a brain cancer, compared with none in a control group that was not exposed to radiation.
About 5 to 7 percent of the male rats exposed to the highest level of radiation developed schwannomas in their hearts, compared with none in the control group. Schwannomas are tumors that occur in cells that line the nerves. The authors concluded the brain and heart tumors were “likely caused’’ by the radiation.
What about female rats?
Oddly enough, the incidence of tumors in females was minimal, barely different from the control group. It is not clear why the results would vary between the sexes, which is one reason some experts are questioning the findings.
What are other caveats?
Even for males, the differences between particular groups of rats and the control group were not statistically significant. Another anomaly was that the rats exposed to the radiation lived longer on the whole than animals in the control group. And schwannomas can occur all over the body, not just the heart, but the study did not find increased rates in other organs.
Also it was unusual that the control group had zero tumors. In previous studies at the National Toxicology Program, an average of 2 percent of rats in control groups developed gliomas. Had that happened in this study, there would have been virtually no difference between the exposed rats and the controls.
“I am unable to accept the authors’ conclusions,” said one reviewer of the study, Dr. Michael S. Lauer, deputy director for extramural research at the National Institutes of Health. Dr. Lauer, whose comments were in an appendix to the report, said it was likely that the findings represented false positives.
“我无法接受作者们的结论，”这项研究的一位评议人迈克尔·S·劳尔博士(Michael S. Lauer)说。他是国家卫生研究院(National Institutes of Health)的院外研究副主任。劳尔的评审意见出现在这份报告的附录里。他说，这些发现可能是错误判断。
The amounts of radiation that rats were exposed to might be higher than what cellphone users typically experience, though toxicology studies often use higher doses to make sure to detect any effect that might exist.
So we can just dismiss this study and go on using our phones?
Not totally. As the authors of the report write: “Given the extremely large number of people who use wireless communication devices, even a very small increase in the incidence of disease resulting from exposure to the RFR generated by those devices would have broad implications for public health.” RFR refers to radio-frequency radiation.
Dr. Otis Brawley, chief medical officer of the American Cancer Society, issued a statement on Friday that called this study “good science,” and called for further research because the animal research used very high signal strengths.
周五，美国癌症学会(American Cancer Society)的首席医疗官奥蒂斯·布劳利博士(Otis Brawley)发表了一项声明，称这项研究是“优秀科学成果”，倡议进行进一步研究，因为动物研究所用的信号强度很高。
But he said, “The NTP report linking radiofrequency radiation (RFR) to two types of cancer marks a paradigm shift in our understanding of radiation and cancer risk.”
Dr. David O. Carpenter, director of the Institute for Health and Environment at the University at Albany, said he thought the study provided backing for the human epidemiological studies that suggested cellphone use was associated with an increased risk of gliomas and acoustic neuromas, a type of schwannoma. “I think this is real,’’ he said, suggesting people used wired earpieces to talk on cellphones.
大卫·O·卡彭特博士(David O. Carpenter)是纽约州立大学奥尔巴尼分校(Albany)健康和环境学院(Institute for Health and Environment)的院长。他说，他认为这项研究为人类流行病学的研究提供了支持，表明使用手机与神经胶质瘤及听神经瘤（神经鞘瘤的一种）的风险增加有关。“我觉得这是真的，”他说。他建议人们在接打电话时使用有线耳机。
What have other studies found?
Dr. Carpenter’s view is not the prevailing one. Many studies have been conducted, including some very large ones like the Million Women Study in Britain, and a Danish study of more than 350,000 cellphone users. There also were studies examining the effects of these radio waves in animals and cells growing in petri dishes. The results are reassuring. There is no convincing evidence of any link between cellphone use and cancer or any other disease.
卡彭特的观点不是主流观点。之前有过很多研究，包括一些很大规模的研究，比如英国的百万女性研究(Million Women Study)，以及丹麦对逾35万手机用户进行的研究。还有些研究是检验这些无线电波对动物以及在皮氏培养皿中生长的细胞的影响。这些研究的结果令人宽慰。没有令人信服的证据表明，使用手机与癌症或其他疾病之间存在联系。
Also, the incidence of brain cancer in the United States has remained steady since 1992, despite the stark increase in cellphone use.
The International Agency for Research on Cancer, part of the World Health Organization, rates cellphone radiation a “possible’’ human carcinogen, based on limited evidence in both people and animals. It gives the same rating to coffee and pickled vegetables.
世界卫生组织(World Health Organization)的国际癌症研究机构(International Agency for Research on Cancer)基于人和动物身上的有限证据，将手机辐射列为“可能”对人类有致癌作用的物质，与咖啡和咸菜属于同一级别。
But don’t we know that radiation causes cancer?
Ionizing radiation, the powerful type from nuclear weapons, nuclear power plants and X-ray machines, is strong enough to knock electrons off atoms and damage DNA. That can cause cancer. But the radiation from cellphones, called radio-frequency radiation, is nonionizing and not known to damage DNA.
So what happens now?
The findings released Friday are preliminary and part of a larger study, so more data will be coming out, probably next year. The existing report will also be reviewed further by more experts.