Lung cancer and tobacco--a global problem.

Lung cancer is the second most common cancer globally, with an estimated 590,000 new cases each year, and is expected to surpass stomach cancer as the most frequent cancer in the near future. Lung cancer is not, as many believe, a problem solely of the developed countries. An estimated 33% of all lung cancer cases occur in developing countries. Approximately 80-90% of all cases of lung cancer in developed countries are caused by tobacco. A clear-cut dose-response relationship among cigarette smokers has been observed, and the risk is greater among those who start smoking at a young age and among those who smoke "high-yield" cigarettes. In China and India, the two most populous nations on earth, from one quarter to one third of all males are addicted to tobacco smoking by the time they are 18 to 20 years old. An epidemic of lung cancer is likely within a decade from the rapidly increasing cigarette consumption in many developing countries. What is needed now is the implementation of national programs of education and legislation with the objective to establish nonsmoking as the cultural norm.