Children with asthma living in multi-family housing who are exposed to certain levels of indoor nitrogen dioxide, a poisonous pollutant byproduct of gas stoves and unvented heaters, are more likely to experience wheeze, persistent cough, shortness of breath and chest tightness.
The nitrogen dioxide levels inside the homes investigated in the study were well below the Environmental Protection Agency's outdoor standards of 53 parts per billion.
The study results were detailed in the first issue for February 2006 of the American Journal of Respiratory and Critical Care Medicine, published by the American Thoracic Society.
Kathleen Belanger, Ph.D., of the Yale Center for Perinatal, Pediatric and Environmental Epidemiology in New Haven, Connecticut, 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 nitrogen dioxide 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.
Among the 242 multi-family housing units studied, 111 (45.9 percent) had nitrogen dioxide concentrations greater than 20 parts per billion. Of the 486 single-family housing units examined, only 45 (9.3 percent) were above 20 parts per billion.
"The association between nitrogen dioxide exposure and respiratory symptoms was limited to children in multi-family housing," said Dr. Belanger. "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 parts per billion was the average concentration of indoor nitrogen dioxide reported in an inner-city population.