An estimated 21 million children in the United States are exposed to secondhand smoke at home. These children suffer more asthma attacks, respiratory infections, and ear infections than kids who live in a smoke-free environment.

    Now a new study finds tobacco smoke in the home may ALSO hinder children's performance at school. Researchers following more than 6,300 British children found that those exposed to secondhand smoke performed more poorly on standardized tests.

    Among 16 to 18 year olds, those living with tobacco smoke were 30% more likely to fail their tests. The descrepancy remained even after scientists accounted for other factors, such as the teenagers' socioeconomic status and whether they were smokers. There have been other studies suggesting that smoke exposure can increase children's attention problems.

    The United States Surgeon General says that no level of secondhand smoke is safe, and it increases many adult health problems, too. Experts recommend parents make every effort to quit smoking, but barring that, never smoke around their children.