Lung cancer is the second most common cancer, accounting for about one out of five malignancies in men 
and one out of nine in women. Unfortunately, over the past several years, while the incidence of lung cancer has 
gradually declined in men, it has been rising alarmingly in women. In 1940 only seven women in 100,000 developed 
the disease; today the rate is 42 in 100,000. And all the evidence points to smoking as the cause.
The majority (85%) of cases of lung cancer are due to long term tobacco smoking. About 10–15% of cases occur in 
people who have never smoked. These cases are often caused by a combination of genetic factors and exposure to 
radon gas, asbestos, second hand smoke, or other forms of air pollution.