送交者: xj 于 2005-4-21, 00:11:50:
回答: 某些肺组织不重生，受损则永远受损，所以吸过烟比没吸烟更危险 由 老中一号 于 2005-4-20, 17:38:21:
The association between air pollution and lung cancer has long been established. However, I believe the striking increase of lung cancer in Beijing is mainly due to smoking.
In China, 60-70% male adults smoke. Those who smoke will have three fold risks of developing cancer. Richard Peto in Oxford showed a reduced risk among ex-smokers using British physicians study with 40 years of follow up. Those who quitted smoking for 20 years had similar risk to those who non-smokers. Those who quitted recently (say five years) had about half of the risk of smokers.
One can examine the lung cancer in females to examine the magnitude of air pollution (forget about second hand smoking). Women are also likely to have a different type of lung cancer.
The colonrectal cancer is mainly due to the change of diet, for example, too much fat and too few fiber thus slowing down the bowl movement.
One puzzle thing is that smoking, air pollution only explain half (?) of lung cancer.