研究生英语课程第二单元.ppt

Part Summary [1~5] A different voice among scientific jargons when scientists implement Proposition 65 When the potential danger of chemicals to cause cancer hits newspapers headlines, the scared public wants laws to protect them from carcinogens. Safe Drinking Water and Toxic Enforcement Act bans chemicals which might cause cancer. On the day when top scientists in California gathered together to discuss the implementation of the states new law, Bruce Ames declared that the levels of man-made carcinogens are generally so low that any danger is trivial compared with the levels of natural carcinogens. Part Summary [6~7] Background of the Scientist [6] Amess message should not be treated lightly as his professional expertise is well acknowledged. [7] Ames does not bow to authorities or defer to public opinion such as represented by the environmental movement. He published a report in Science magazine with substantial data to show that most cancer risks created by man are trivial as compared with everyday natural risks. He believes overemphasizing the trivial and uncertain risks will distract our attention from greater risk factors. Part Summary [8~10] Background of Amess research [8~10] When it occurred to Ames that nobody knew how chemicals in our food affected human genes and there was no easy way to find out, he developed the Ames test, a carcinogen test using bacteria. Then he began to use the Ames test on household products for carcinogens. When many common household products tested positive, new regulations and bans on certain chemicals resulted. Thus he became a hero of the environmentalists. Part Summary [11~14] A new discovery [11~12] When public concern over manmade carcinogens continued to rise, Ames found that many of the natural substances also tested positive. He realized that, like most people, he had been naive to assume that nature is benign. [13~14] Seeing how the environmental movement supported Proposition 65, Ames decided it was his duty to enlig