Secondhand smoke is the smoke from the burning end of a cigarette, pipe, or cigar and the smoke breathed out by a smoker. Secondhand smoke exposure causes a number of serious health effects in young children, such as coughing and wheezing, bronchitis and pneumonia, ear infections, reduced lung function, and worsened asthma attacks. Secondhand smoke is an irritant which may trigger an asthma episode, and increasing evidence suggests secondhand smoke may cause asthma in children.
The Environmental Protection Agency estimates that between 200,000 and 1,000,000 children with asthma have their condition made worse by exposure to secondhand smoke. Secondhand smoke can also lead to buildup of fluid in the middle ear, the most common cause of children being hospitalized for an operation.
(From Tools for Schools)