A study of Hong Kong students suggests that children and teenagers exposed to secondhand smoke at home may get poorer grades than their peers from smoke-free homes. Secondhand smoke is a well-known health threat to children, being linked to increased risks of asthma, as well as bronchitis, pneumonia and other respiratory infections. Other studies found a connection between smoking during pregnancy and higher risks of childhood behavior problems and attention-deficit/hyperactivity disorder. Some studies found that children exposed to cigarette smoke in the womb may trail from their peers when it comes to cognitive abilities like reasoning and remembering. However, whether secondhand smoke itself it to blame still remains unclear. Researchers found in the new study that of the 23,000 11- to 20-year-old non-smoking students, one-third who lived with at least one smoker, were more likely to describe their own school performance as “poor.” Click here to find out more! Of students who said they were exposed to secondhand smoke at home at least five days a week, 23 percent said their school performance was poor when compared with their classmates’. The scientists accounted for certain other factors, like parents’ education levels and the type of housing. They found that students’ exposure to secondhand smoke was linked to a 14 percent to 28 percent greater risk of poor school performance, depending on how frequent the exposure was. Dr. Sai-Yin Ho and colleagues at the University of Hong Kong reported the study in the Journal of Pediatrics. The study did not prove that secondhand smoke was the reason for poorer grades. The study had a number of limitations, including its reliance of students’ ratings based on their own academic performance and exposure to secondhand smoke. Ho’s team said that future studies should include objective measures of secondhand-smoke exposure as well as official school records. The researchers also could not account for the full range of factors that might coincide with both secondhand smoke exposure and children’s school performance. The researchers wrote that it is biologically plausible that the many toxic compounds in tobacco smoke could affect children’s cognitive abilities. There are many established reasons for parents to quit smoking regardless of whether secondhand smoke hurts a child’s school performance. The researchers said that these findings offer another potential reason for parents to “eliminate smoking at home” and warn their children to avoid secondhand exposure.