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  3. Can electricity cause cancer? In a society that literally runs on electric power, the very idea seems preposterous. But for more

Can electricity cause cancer? In a society that literally runs on electric power, the very idea seems preposterous. But for more

admin2017-11-28  71
问题     Can electricity cause cancer? In a society that literally runs on electric power, the very idea seems preposterous. But for more than a decade, a growing band of scientists and journalists has pointed to studies that seem to link exposure to electromagnetic fields with increased risk of leukemia and other malignancies. The implications are unsettling, to say the least, since everyone comes into contact with such fields, which are generated by everything electrical, from power lines and antennas to personal computers and micro-wave ovens. Because evidence on the subject is inconclusive and often contradictory, it has been hard to decide whether concern about the health effects of electricity is legitimate — or the worst kind of paranoia.
    Now the alarmists have gained some qualified support from the U. S. Environmental Protection Agency. In the executive summary of a new scientific review, released in draft form late last week, the EPA has put forward what amounts to the most serious government warning to date. The agency tentatively concludes that scientific evidence "suggests a casual link" between extremely low-frequency electromagnetic fields — those having very long wave lengths — and leukemia, lymphoma and brain cancer. While the report falls short of classifying ELF fields as probable carcinogens, it does identify the common 60-hertz magnetic field as " a possible , but not proven, cause of cancer in humans. "
    The report is no reason to panic — or even to lost sleep. If there is a cancer risk, it is a small one. The evidence is still so controversial that the draft stirred a great deal of debate within the government, and the EPA released it over strong objections from the Pentagon and the White House. But now no one can deny that the issue must be taken seriously and that much more research is needed.
    At the heart of the debate is a simple and well-understood physical phenomenon: When an electric current passes through a wire, it generates an electromagnetic field that exerts forces on surrounding objects. For many years, scientists dismissed any suggestion that such forces might be harmful, primarily because they are so extraordinarily weak. The ELF magnetic field generated by a video terminal measures only a few milligauss, or about one-hundredth the strength of the earth’s own magnetic field. The electric fields surrounding a power line can be as high as 10 kilo volts per meter, but the corresponding field induced in human cells will be only about 1 millivolt per meter. This is far less than the electric fields that the cells themselves generate.
    How could such minuscule forces pose a health danger? The consensus used to be that they could not, and for decades scientists concentrated on more powerful kinds of radiation, like X-rays, that pack sufficient wallop to knock electrons out of the molecules that make up the human body. Such "ionizing" radiations have been clearly linked to increased cancer risks and there are regulations to control emissions.
    But epidemiological studies, which find statistical associations between sets of data, do not prove cause and effect. Though there is a body of laboratory work showing that exposure to ELF fields can have biological effects on animal tissues, a mechanism by which those effects could lead to cancerous growths has never been found.
    The Pentagon is far from persuaded. In a blistering 33-page critique of the EPA report, Air Force scientists charge its authors with having "biased the entire document" toward proving a link. "Our reviewers are convinced that there is no suggestion that (electromagnetic fields) present in the environment induce or promote cancer," the Air Force concludes. "It is astonishing that the EPA would lend its imprimatur on this report." Then Pentagon’s concern is understandable. There is hardly a unit of the modern military that does not depend on the heavy use of some kind of electronic equipment, from huge ground-based radar towers to the defense systems built into every warship and plane.
Why did the Pentagon object to the release of the report? Because______.
选项 A、it may stir a great deal of debate in the government
B、almost every modern military unit depends on the heavy use of some kind of electronic equipment
C、the authors of the report prove a link between the use of electronic equipment and cancer
D、they had different arguments
答案B
解析 事实细节题。第三段第三句只是提到五角大楼和白宫反对“极低频电磁场与疾病之间存在联系”，但并没有说明原因，继续向下阅读可发现第七段对原因作出了说明。本段最后一句指出，现代军事的任何部门都依赖于电子设备的大量应用，而这也是五角大楼和白宫反对环境保护局结论的原因，故答案为[B]项。
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