This study strongly suggests that housing type contributes to children's exposure to tobacco smoke, despite the best intentions of parents and is the first to show significant evidence of increased tobacco smoke exposure in the blood of children who live in multi-unit housing.
The U.S. surgeon general has said that there is no safe level of exposure to tobacco smoke. Also, children exposed to secondhand tobacco smoke are at greater risk for a variety of illnesses, such as respiratory infections, asthma and sudden infant death syndrome.
In this study, data from more than 5,000 children ages 6 to18 in a national database (National Health and Nutrition Examination Survey 2001-2006) was analyzed to see if there was any relationship between their smoke exposure and their housing type.
The researchers measured blood levels of cotinine, a chemical commonly used to test for tobacco exposure.
Overall, using the most sensitive cutoff for tobacco smoke exposure, more than 84 percent of children in multi-unit housing had been exposed to tobacco smoke, compared to almost 80 percent of children living in attached houses and 70 percent of children in detached houses.
At every cutoff level of cotinine, children living in apartments had higher rates of exposure.
"Parents try so hard to protect their children from dangers, such as tobacco smoke. It's surprising to see these results and realize that too many parents have no control over whether their children are exposed to secondhand smoke in their own homes," said Karen Wilson, MD, MPH, an assistant professor of Pediatrics at the University of Rochester Medical Center's Golisano Children's Hospital and lead author of the paper.
Controlling for other factors such as poverty and age, children living in apartments had an increase in cotinine of 45 percent over those living in detached houses.
Cotinine levels were highest for children who were under 12, African American and living below the federal poverty level.
The researchers hypothesize some of the tobacco exposure may have come from family members who only smoke outside, but carry in tobacco residue on their clothes, they suggest this is unlikely to explain all of the difference since there are many more exposed children than adult smokers.
Instead they conclude tobacco smoke may have seeped through walls or shared ventilation systems. Earlier studies have shown that tobacco smoke contaminates non-smoking units of multi-unit dwellings.
"This study is an important piece of evidence supporting universal smoke-free multi-unit housing," said Jonathan Winickoff, MD, MPH, of the MassGeneral Hospital for Children and the senior author of the study.
Results from this study could further encourage landlords and apartment building owners to adopt smoke-free policies.
"When landlords set a completely smoke-free policy they will enjoy lower fire risk and insurance costs, lower clean up costs between tenants, and they will be fostering a healthier home for everyone in the building," said Winickoff.
Winickoff, who is also an associate professor of Pediatrics at Harvard Medical School, notes smokers are generally very respectful of not exposing children and non-smokers to tobacco smoke in indoor environments, but says, "this research will help promote the notion that it is never acceptable to smoke indoors, even in your own unit, because the smoke get into the bodies of children in other units."
The study authors also stress the importance of making sure that resources for quitting smoking are provided for smokers whose buildings become smoke-free.
"Hopefully this research and the movement towards smoke-free housing will open up programs and opportunities for more folks to quit smoking. Promoting the use of the free quit-lines in every state is a great way to facilitate these efforts," said Wilson.
The study released online today by the journal Pediatrics and will appear in the print edition in January 2011.
