A new study has found that building no smoking housing zones is a good idea to save children from passive smoking. With smoking bans being imposed at places like offices, restaurants and other public places, there’s only place remaining where smokers can still light up—inside their homes.

In a study of tobacco exposure from secondhand smoke in more than 5,000 children, researchers led by Dr. Karen Wilson at University of Rochester found that youngsters aged 6 to 18 years who lived in multi-unit housing had a 45% increase in a chemical byproduct of tobacco in their blood compared with children who lived in detached family homes. And these were youngsters who lived in units where nobody smoked inside the apartment itself, meaning that the exposure was occurring primarily via secondhand smoke drifting in from other units.

This study, released online today by the journal Pediatrics, strongly suggests that housing type contributes to children’s exposure to tobacco smoke, despite the best intentions of parents.

The finding of the study that children living in apartments are exposed to secondhand smoke even when no one smokes inside their own unit has once again emphasized the need for smoke-free multi-unit housing.

This new study from the University of Rochester Medical Center, MassGeneral Hospital for Children and the American Academy of Pediatrics’ Julius B. Richmond Center for Excellence is the first to show significant evidence of increased tobacco smoke exposure in the blood of children who live in multi-unit housing. It will appear in the January 2011 issue of Pediatrics.

The U.S. surgeon general has said that there is no safe level of exposure to tobacco smoke. 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, 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. While some of the tobacco exposure may have come from family members who only smoke outside, but carry in tobacco residue on their clothes, study authors 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.

The study, which was funded by the Julius B. Richmond Center of Excellence of the American Academy of Pediatrics, through a grant from the Flight Attendant Medical Research Institute, analyzed data from more than 5,000 children ages 6 to18 in a national database (National Health and Nutrition Examination Survey 2001-2006) to see if there was any relationship between their smoke exposure and their housing type. Cotinine levels were highest for children who were under 12, black and living below the federal poverty level. Previous studies have shown that children with cotinine levels indicating even very low amounts of tobacco smoke exposure have delayed cognitive abilities and decreased antioxidant levels.

“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. “More and more landlords, in all 50 states, know that they can set the smoke-free policy for their buildings, and with 80 percent of the population not smoking, market demands strongly favor smoke-free status. 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.”

“In general, people who smoke are very respectful of not exposing children and non-smokers to tobacco smoke in indoor environments. 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,” said Winickoff, who is also an associate professor of Pediatrics at Harvard Medical School.

The authors also stress the importance of making sure that tobacco cessation resources 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 quitlines in every state is a great way to facilitate these efforts,” Wilson said.

Previous studies have documented the extent to which secondhand smoke can show up among nonsmokers, but Wilson says the amount of exposure in the children in her study was “a little higher than I expected.” Among white children living in apartment buildings, 99% showed levels of cotinine, the tobacco byproduct, in their blood, while 96% of African American children did as well.

While certain foods such as eggplant and tomatoes do contain cotinine, those levels are likely to be negligible given to the amounts found in the children's blood, says researchers. And although recent studies have raised the possibility that another source of tobacco exposure known as thirdhand smokers, which involves physical tobacco residue that may remain on the clothing and hair of smokers, could be contributing to the higher cotinine levels among these children, scientist say that exposure is also unlikely to explain the entire amount recorded in the subjects of her study.

The research also brings in the tussle between child rights as well as non smoking adults to protect themselves from various ailments of passive smoking and right of smokers to light up in their own house. They argue that it is the basic right of any individual to live in a healthy environment.

This new study makes clear that multi-housing must be completely smoke-free if we aspire for a healthy and pollution free environment around us.