Passive smoke exposure from parents who smoke is associated with respiratory symptoms in infants and toddlers who present to the emergency department with wheezing. The risk of developing asthma is 2.5 times greater in young children with mothers who smoke 10 or more cigarettes/day indoors compared with mothers who don't smoke or who smoke less than 10 cigarettes/day. The recent increases in the prevalence and severity of childhood asthma may be attributable in part to the increase in the prevalence of smoking among mothers.
In a study of children of all ages, those living in a smoking household were found to be 63% more likely to have asthma than those residing in a nonsmoking household. In a survey of more than 7,000 children and adolescents under 18 years of age, those whose mothers smoked were more likely to experience wheezing respiratory illness than children with nonsmoking mothers. The investigators estimate that maternal smoking is responsible for 380,000 cases of childhood asthma.