ok... rule of thumb... 1 pack a day gives a 10% lifetime risk of lung cancer. we can detect cigarette stuff in the bloood so very accurately we can detect the 1% increase in risk from second hand smoke (1 in 1000 lifetime risk). You are looking at about a 1% lifetime risk BUT, with some significant risk of wrinkles, heart disease, other cancers that also are increased. The heart disease risk is not so linear as the lung cancer and 5 cigarettes is a significant increase risk of heart disease that is MORE than proportional to the number of cigarettes and more women die of heart than cancer. Lung cancer risk declines and goes to about the same as a never smoker by about 10 years. Heart risk declines Very rapidly.. 1 year or less. BUT there is some residual damage to lungs and blood vessels and wrinkles that doesn t all go away with quitting.