About half of adult smokers who live with young children say they don't smoke in the house. But that leaves the rest who do.

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And the children of these at-home smokers â€"according to a study just published in the journal Pediatrics â€" are missing more days of school.

The study found that children living with a smoker in the house miss about one extra day per year. And if two adults in the house smoke, children miss 1.54 more days compared to kids from nonsmoking households.

Just about everybody knows that second-hand smoke increases the risk of respiratory ailments and asthma attacks, but it wasn't clear how illnesses related to smoking influenced absenteeism.

 

School absenteeism, as the study's authors note, is an easy-to-measure marker that can flag all sorts of illness. The researchers conclude that up to one-third of all missed school days by children of smokers can be attributed to the exposure of second-hand smoke.

"It was a surprise," says lead author Douglas Levy of the Mongan Institute for Health Policy at Massachusetts General Hospital. "A good chunk of these kids missed-school days is just due to secondhand smoke exposure." In their analysis, the researchers adjusted the figures to account for differences in household income, education and several other factors.

The educational impact of these absences isn't entirely clear, but missed days can't be good. But, in any case, the financial toll is significant. When these children get sick working parents need to stay home. And that adds up to lots of lost wages â€" about $227 million a year â€" the researchers figure.

Levy explains that about half of the children living with a smoker are in low-income families, so the hardship for them could be significant. "If we could eliminate second-hand smoke exposure" says Levy. "It would help a lot."