Air Pollution Hits Children With Asthma Hardest, USC Study Finds

The USC study, which began in 1993, is unique in that it focuses on the long-term effects of pollution on children -- a group considered especially vulnerable as they spend a lot of time playing outdoors.

The upshot of this research is that children with asthma really are more affected by severe air pollution than other children. They are, according to the USC research, a group who should receive careful monitoring of their activities on days when the air quality is poor.

The latest research is published in the September issue of Environmental Health Perspectives.

In the study, Rob McConnell, M.D., and colleagues in the Division of Occupational and Environmental Health, show that living in communities with higher levels of "particulates" and related pollutants, nitrogen dioxide and acid, in the air is associated with higher rates of bronchitis and phlegm among children with a doctor diagnosis of asthma. Particulate matter refers to microscopic suspended particles of dust, including products of combustion from automobiles or even manufacturing. They can lodge in the lungs, causing respiratory problems.

The study took place in 12 middle-class suburban communities in Southern California. The study investigators recruited 150 fourth graders, 75 seventh graders, and 75 tenth graders from each of the 12 communities to participate in the study. The parents of each child were asked to fill out a questionnaire about their child's chest symptoms in the past 12 months. They were also asked questions about their home environment, including the presence of smokers in the home, cockroaches, pets, gas stoves, bedroom carpets, and mildew. Many of these are known to trigger attacks of asthma. Measurements of a variety of pollutants were collected from outdoor air monitoring instruments in each of the communities.

McConnell et al. found that children with asthma who lived Southern California communities with high levels of pollutants were more likely to have had bronchitis and phlegm, reflecting exacerbation of asthma. These results were not explained by the presence of common indoor triggers of asthma.

Already, public health authorities in Southern California have taken action to prevent problems in children with asthma. Air quality has improved dramatically over the past several decades as a result of efforts to reduce emissions from automobiles and other sources of pollution. Despite the progress made in reducing pollution, the USC team's results indicate that children with asthma remain at risk in today's environment.