According to the U.S. Department of Health and Human Services, there is no safe level of first- or second-hand smoke, and more than 20 million Americans have died because of smoking, including 2.5 million nonsmokers from secondhand smoke. If smoking rates remain as they are, the HHS predicts 5.6 million of children 18 and under today will die early from smoking.
HHS Health Consequences of Smoking, Surgeon General Fact Sheet
Surgeon General’s 50th Anniversary Report on Smoking and Health