吸煙有害健康（二）
So what are the risks? Here's what tobacco's critics say:
CANCER
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.
那么吸煙究竟有什么危害呢?還是聽聽煙草批評家們的說法：
癌癥
疾病防治中心說，吸煙是導致美國每年151322位癌癥患者死亡的罪魁禍首。這些死亡者中的大多數――116990人是死于肺癌。疾病防治中心認為，男性煙民死于肺癌的可能性是非吸煙者的22倍。女性煙民死于肺癌的可能性是非吸煙者的 12倍。
統計數據研究早就表明，不吸煙的人比煙民長壽，而且自20世紀50年代以來，科學家們通過統計資料，已經發現了吸煙和肺癌發病率之間的相互關系。
而今年早些時候，貝克曼研究所的格爾德?普法伊費爾所作的一項研究確切地指出了卷煙煙霧中固有的致癌物，這些致癌物襲擊的目標是一種基因的某些部分，人們已經發現，這種基因在一些癌癥中很突出。 普法伊費爾在《科學》雜志上寫道，吸煙使p53基因發生改變，這種基因在正常情況下起著防癌的作用，但在發生突變時，就會加快癌癥的發展。
美國癌癥協會發表的另一份研究報告說，尼古丁含量低的卷煙并不能減少患癌癥的可能性，它們實際上是引起一種進入到肺組織深層的癌癥的罪魁禍首。
而其他的癌癥也受吸煙的影響。今年年初，美國癌癥協會的一份研究報告表明，吸煙使男性死于前列腺癌的危險增加了，而其他的一些研究把吸煙同患上其他癌癥(包括喉癌、乳腺癌和結腸癌)的危險的增加聯系到了一起。
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