Short-term effects of outdoor pollution levels on asthma symptoms and lung function in children

Apr 16 2008

A new study reports that inner-city children with asthma may be particularly vulnerable to air pollution at levels below current air quality standards.

The study, available online, analyzes the short-term effects of outdoor pollution levels on asthma symptoms and lung function in children. The study was supported by the National Institutes of Health (NIH) and the Environmental Protection Agency (EPA).

Using data collected from the NIAID Inner-City Asthma Study (ICAS), researchers examined 861 children with persistent asthma, aged 5 to 12 years, living in low-income areas in seven U.S. inner-city communities: Boston, the Bronx, Chicago, Dallas, New York City, Seattle and Tucson. Over two years, the researchers regularly monitored the children's asthma symptoms, breathing function, and school absences, and obtained daily outdoor pollution measurements from the EPA's Aerometric Information Retrieval System. Every six months, they tested lung function twice-daily over a two-week period. They also asked the children's parents for their observations of their children's symptoms.

Results revealed that children had significantly decreased lung function following exposure to higher concentrations of the air pollutants sulfur dioxide, airborne fine particles, and nitrogen dioxide. Higher nitrogen dioxide levels and higher levels of fine particles also were associated with school absences related to asthma, and higher nitrogen dioxide levels were associated with more asthma symptoms. Because nitrogen dioxide is derived mainly from motor vehicle exhaust, these data provide evidence that car emissions may be causing adverse respiratory health effects in these urban children who have asthma.

Previous studies have documented the adverse respiratory effects of very high levels of outdoor pollutants. However, this study involves a larger cohort of inner-city asthmatic children and a more comprehensive evaluation of respiratory health effects than prior studies of this type. The study's authors report that inner-city children with asthma experience adverse health effects from air pollutants even when air pollution levels are within the current air quality standards of the Environmental Protection Agency. These findings raise questions about the current air quality standards and suggest that part of overall asthma management for children living in inner cities may need to include efforts to reduce exposure to air pollutants.