Children who live with smokers miss more school due to illness than those who live in households with non-smokers, according to a new study published in the journal Pediatrics.

Researchers analyzed data from the 2005 National Health Interview Survey that tracked, among other things, how many days of school children aged 6 to11 missed and the reason for their absence.

They found children living with one or more smokers in the home missed one to two more days of school per year on average, than those who lived with non-smokers.  The research suggests that families could reduce absenteeism by 24 to 34 % if smoking was eliminated from their households.

According to the study, about one third of children in the United States live with a smoker. Among children aged 3 to 11, at least 56% have detectable levels of a chemical called serum cotinine, an indication of tobacco smoke exposure. Cotinine is a breakdown of nicotine and can be measured by analyzing levels in the blood, urine or saliva. Researchers say this establishes a link between household smoking and two specific respiratory illnesses.

“Kids living with people smoking in the home were more likely to have ear infections and chest colds,” Dr. Douglas Levy, the study’s principal investigator and Assistant in Health Care Policy at the Mongan Institute for Health Policy said. “Among kids who were living with smokers, a quarter to one-third of the days they missed from school can be attributed to the fact that they live with someone who smokes in the home.”

The study found that having multiple smokers in the home resulted in more  illnesses reported and days of school missed. For example, a child living with 2 or more adult smokers had more ear infections- three or more-in a year, than a child living with no smokers or even just one smoker.

An increase in illness was not the only consequence smoking at homr. Levy says there is a financial burden as well because parents or other caregivers must take off work to care for sick children.

“When kids are home from school, particularly young kids, the cost overall is $227 million dollars per year. All due to the extra days that we see kids missing school because of secondhand smoke exposure,” said Levy.

Adults in non-smoking households were more educated, had higher incomes and were more likely to be Hispanic the study found. Homes with 2 or more smokers also had higher incomes but were more often white. About half the kids in the study that lived with a smoker were from low-income households Levy said. His advice to parents? “If you are a smoker do not smoke around your kids whether it be at home or in the car. Even better advice is to try to quit smoking.”