Risk from tobacco and potentials for health gain

Evidence that smoking tobacco harms health has accumulated ol er 200 years, but was largely ignored before 1350, when five case-control studies associ ated smoking with the development of lung cancer. The idea that it might ca use the disease was greeted with scepticism, and it was nearly 10 years bef ore it became generally accepted. By then there had been additional evidenc e from cohort studies, and known carcinogens had been identified in tobacco tars. Cigarette smoking has now been positively associated with some 40 causes of death and negatively associated with eight or nine. A few of the associati ons are due to confounding, but the great majority reflect causality. In se veral instances cigarette smoking increases the risk of death ten-fold, and altogether it doubles the annual risk of death at all ages combined, in bo th sexes. Tobacco smoke in the environment also has a small effect on the h ealth of non-smokers, particularly in infancy and childhood, but also to so me extent later in life. Nearly a quarter of all deaths in men and a tenth in women in industrialise d countries in 1990 were attributed to smoking, giving a total of 1.8 milli on a year. In 20-30 years' time the total is estimated to rise to 10 millio n a year, with 7 million in low income countries, if smoking habits persist unchanged.