Secondhand smoke (search) may lower kids’ math and reading scores, putting more than 22 million U.S. kids at risk for reading problems.

The estimate comes from a study of almost 4,400 American kids aged 6-16. Researchers tested the children’s math, reading, spatial, and memory skills. They also screened the children’s blood samples for a chemical derived from nicotine.

The chemical — called cotinine (search) — showed tobacco smoke exposure. Since all participants said they hadn’t used tobacco products for at least five days, they must have breathed someone else’s smoke — most likely, at home.

Smoke exposure went hand in hand with lower test scores. Children with the most cotinine in their blood scored significantly lower on all four tests, compared with those with the lowest cotinine levels.

Reading, math, and spatial skills suffered most. Short-term memory wasn’t as affected.

“Reading ability was especially sensitive to environmental tobacco smoke exposure,” according to researcher Kimberly Yolton of Cincinnati Children’s Medical Center. Her findings appear in the January issue of Environmental Health Perspectives.

Even a little smoke exposure caused a drop in reading and other skills.

Test scores fell as smoke exposure rose. That is, the higher the child’s cotinine levels, the lower their scores were in reading, math, and spatial skills.

By Miranda Hitti, reviewed by Michael W. Smith, MD

SOURCE: Yolton, K. Environmental Health Perspectives, January 2005; vol 113: pp 98-103.