The tobacco is treated with chemicals so that it will keep burning even when it is not being smoked. Secondhand smoke contains up to 4,000 chemicals, including trace amounts of poisons like formaldehyde, arsenic, DDT and cyanide. More than 40 of the substances in ETS are know to cause cancer. Many more cause irritation of the lungs and airways. Group A carcinogens are the most harmful.
Children are at special risk of lung damage and illness from inhaled smoke.
Studies have shown a clear link between ETS and asthma in young people. Passive smoking worsens asthma in teens and may cause up to 26,000 new cases of asthma each year. These infections in turn lead to thousands of hospitalizations of children each year. The incidence of sudden infant death syndrome quadruples if either mother or both parents are smokers. Children with allergies and nasal congestion who are also exposed to tobacco smoke are up to six times more likely than others to have persistent middle ear infections requiring the surgical insertion of tubes.