单项选择题

Read the following passage carefully and then decide whether the statements which follow are true(T)or false(F). Do Cell Phones Cause Cancer There are safety-warning labels on cigarettes and alcohol. Now some groups are advocating that similar cautions be printed on cell phones. Recently, a bill in the Maine state senate proposed a label warning users, especially children and pregnant women, of the risks of brain cancer from electromagnetic radiation emanating from the device. But the Maine legislature voted down the bill in March, stating that the scientific evidence does not indicate a public health risk. Yet, the debate rages on. Can cell phones really cause cancer Supporters of the Maine legislation argued that uncertainty about the long-term effects of cell phone radiation warranted public safety notices. They also pointed to a handful of European studies that linked brain and auditory nerve tumors with using cell phones for more than 10 years and at younger ages. "I think my short answer is that the evidence isn"t 100 percent, but there"s a strong indication that, yes, cell phone use does cause cancer(over a long period of time), " said David Carpenter, director of the Institute for Health and Environment at the University of Albany, and an advocate for the Maine bill on cell phone warnings. Carpenter points to a 2007 meta-analysis that associated ipsilateral auditory nerve tumors(acoustic neuromas)with people who had used cell phones for at least 10 years, as well as a 2009 Swedish study that found a heightened risk for brain tumors among people who had used cell phones for at least 10 years, especially for those under 20 years old. Not surprisingly, cell phone industry insiders disagree, " " The peer-reviewed scientific evidence has overwhelmingly indicated that wireless devices, within the(radiation)limits established by the FCC, do not pose a public health risk or cause any adverse health effects, " said John Walls, vice president of public affairs for CTIA—The Wireless Association, an international trade group that represents the wireless telecomm industry. For instance, 2001 Danish study and 2006 follow-up found no relationship between cancer risk and long-term cell phone use among more than 400, 000 users. In addition, a statistical review from the National Institutes of Cancer revealed no rise in cancer incidence rates from 1975 to 2005 in relation to the rise in cell phone usage. Joshua Muscat, a public health science professor at Pennsylvania State University who has studied the cancer-causing potential of cell phone radiation, also questions the connection. "There is no known mechanism by which radio frequency fields generated by cell phones can cause cancer because cell phone radiation is non-ionizing, " Muscat said. Nevertheless, when you press a cell phone against your ear while it"s in use, head and brain tissues can absorb that vibrating, low-frequency radiation and heat. Because of that radiation effect, the Federal Communications Commission(FCC)sets specific absorption rates(SARs)that dictate the maximum amount of radiation cell phones and mobile devices can give off. " The power output from these phones is extremely low, " Muscat told Discovery News. However, David Carpenter counters that the SARs don"t take into account the potential long-term damage of close-range exposure to heat-inducing radiation, especially in children. "Those(FCC)levels are set by engineers and physicists, and those aren"t the people who should be setting health-based standards, " he said. Carpenter thinks that the results from a large, 13-country study called Interphone, which consists of a series of 16 case-controlled studies conducted between 2000 and 2005, could finally settle the debate. Each of the Interphone studies recruited at least 100 people who had developed brain cancer or certain types of tumors, along with a healthy control group. But it"s been hampered by methodological shortcomings. In many cases, the group was asked to describe their cell phone habits, which critics contend led to recall bias. So far, it still hasn"t rendered a final verdict. For now, the National Cancer Institute, American Cancer Society, U.S. Food and Drug Administration, among other leading health agencies and organizations, aren"t ringing the alarm bells. For one thing, scientists have yet to pinpoint how the low-frequency cell phone radiation could cause cancer. "Cell phone radiation"s effect in the body appears to be insufficient to produce the genetic damage typically associated with developing cancer, " said Robert N. Hoover, director of epidemiology for the National Cancer Institute, in an official statement to Congress. " To date, no alternative mechanism about how this exposure might result in cancer has been vetted adequately. " Until scientists can unmask that " mechanism, " Carpenter urges consumers to play it safe and text message or hold cell phones away from their ears to limit radiation exposure. Even Muscat from Penn State leaves a space—albeit a narrow one—for caution. "It is a legitimate concern in the sense that there may be some unknown, undiscovered mechanism that could be promoting the development of cancer, " Muscat said. "This seems unlikely, but if one looks at other scientific disciplines such as cosmology or particle physics, there are often paradigm shifts that occur with new discoveries. " Cell phone radiation is non-ionizing and therefore exposure can strip electrons from atoms and molecules and directly damage cellular DNA, like X-rays can.