Smoking tobacco releases toxic and harmful substances into the body. It produces carbon monoxide, sulfur dioxide, hydrogen sulfide, formic acid, cyanhydric acid, acetic acid, nicotine, ammonia, arsenic, lead, cobalt and other toxic gases and acids. Smoking can cause diseases of the respiratory tract, discoloration of teeth, shorten life expectancy by 1-4 years, vasoconstriction, reduced activity levels, financial strain, and increase the risk of drug addiction. Secondhand smoke exposes non-smokers to these harmful substances, as smokers exhale 50% of the smoke into the air. Smoking during pregnancy can also retard fetal development. Survey data shows smoking rates generally increase