Study: Asthmatic Children In Multi-Family Housing Affected By Indoor Nitrogen Dioxide

Children with asthma living in multi-family housing who are exposed to certain levels of indoor nitrogen dioxide (NO2), a pollutant byproduct of gas stoves and unvented heaters, are more likely to experience wheezing, persistent cough, shortness of breath and chest tightness.

The study results were detailed in the Feb. 1 issue of the American Journal of Respiratory and Critical Care Medicine, published by the American Thoracic Society (see abstract at

Kathleen Belanger, Ph.D., of the Yale Center for Perinatal, Pediatric and Environmental Epidemiology in New Haven, Conn., along with four associates, studied 728 children with asthma, younger than 12, who were exposed to nitrogen dioxide in their home.

According to the authors, the 2000 U.S. Census indicated that more than half of U.S. households use gas and that the primary source for residential NO2 levels was a gas-fueled cooking appliance.

In the study, the average level for nitrogen dioxide in homes with electric stoves was 8.6 parts per billion; in homes with gas stoves, the level was 25.9 parts per billion (ppb).

Among the 242 multi-family housing units studied, 111 (45.9 percent) had nitrogen dioxide concentrations greater than 20 ppb. Of the 486 single-family housing units examined, only 45 (9.3 percent) were above 20 ppb.

"The association between nitrogen dioxide exposure and respiratory symptoms was limited to children in multi-family housing," Belanger said. "To date, this is the largest study to examine the effects of nitrogen dioxide on children with asthma. The study population was quite diverse and included both white and non-white children living in single-family and multi-family homes, and children living in urban and suburban environments."

According to the authors, a prior study in 2005 showed that 20 ppb was the average concentration of indoor nitrogen dioxide reported in an inner-city population.

At the end of the study enrollment period, a trained research assistant visited each home and collected extensive information from the study participant's mother on the family's ethnicity, education, smoking history, house characteristics and use of a household appliance fueled by natural gas. Mothers were asked the number of days during the preceding month that their child experienced respiratory symptoms. They also were questioned about medications the child took for both asthma attacks and disease maintenance.

"Children using maintenance medications were more likely to have respiratory symptoms than children who did not, indicating more severe asthma," Belanger said.

NO2 levels were measured in each participant's main living area for 10 to 14 days after the initial enrollment visit.

Kathleen Belanger -- (scroll down for her contact information)

This article originally appeared in the 02/01/2006 issue of Environmental Protection.

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