吸烟有害健康Before Dr. Luther L. Terry, then the Surgeon General of the United States, issued his office’s first "Report on Smoking and Health" more than 30 years ago, thousands of articles had already been written on the effects of tobacco use on the human body.
 Tobacco companies had countered the reports--which purported to show links between smoking and cancer and other serious diseases--with denials and competing studies.
 So in 1964, Terry and his Advisory Committee on Smoking and Health knew they were stepping into a major pit of controversy when they announced "cigarette smoking is a health hazard of sufficient importance in the United States to warrant appropriate remedial action".
 It was America’s first widely publicized acknowledgment that smoking cigarettes is a cause of serious diseases.
 But the issue wasn’t settled in 1964, nor is it settled in 1997, despite literally thousands more studies--and litigation that has forced at least one tobacco company to admit what some activists say they knew all along: cigarette smoke is hazardous to your health.
6] More than 30 years--and more than 20 Surgeon General reports--later, the issue appears headed for settlement in the courtroom rather than the laboratory.
So what are the risks? Here’s what tobacco’s critics say:
 The Centers for Disease Control and Prevention says cigarette smoking is responsible for 151,322 cancer deaths annually in the United States. Most of those--116,920--are from lung cancer. The CDC says men who smoke are 22 times more likely to die from lung cancer than non-smokers. Women who smoke are 12 times more likely to die from the disease.
 Statistical studies have long shown that people who don’t smoke live longer than people who do and scientists have seen statistically the correlation between smoking and incidences of lung cancer since the 1950s.
 But a study earlier this year by Gerd Pfeifer of the Beckman Research Institute pinpointed specific carcinogens in cigarette smoke that target parts of a gene already known to be prominent in some cancers.
 Pfeifer wrote in Science that cigarette smoke causes changes in the gene p53, which protects against cancer when normal but promotes cancer growth when mutated .
 Another study, published by the American Cancer Society, said that low-tar cigarettes offered no relief from the potential of cancer, and in fact were responsible for a type of cancer that reaches deeper into lung tissue.
 Other cancers are also affected by cigarette smoke. An American Cancer Society researcher reported earlier this year that smoking increased men’s risk of dying of prostate cancer, while other studies have linked tobacco use to increased risk of other cancers, including throat, breast and bowel cancer.