And those that do have a very small range." Like most drug prohibitions, these measures haven't stopped people from buying the products they want
In the USA, the relative risk of lung cancer in current smokers (relative to never smokers) was 11.5 in men and 2.7 in women in the Cancer Prevention Study I (CPS I) conducted by the American Cancer Society during 19591965, whereas it was 23.3 in men and 12.7 in women in CPS II (US Department of Health and Human Services, 2004)
Except that there isnt just one
One JAMA study compared post-surgery risks for 125,000 people who smoke, 78,000 people who quit smoking at least a year before surgery and 400,000 people who have never smoked
A second reason is that one does not know whether these mixtures behave according to a linear combination of the effects of their individual constituents or whether synergistic effects occur