April 22, 2010 -- Ozone and pollution emitted by traffic have been linked to spikes in asthma-related emergency room visits among children, particularly during summer, according to a large, population-based study.
Researchers from the Rollins School of Public Health at Emory University in Atlanta collected data on more than 91,000 emergency room visits that took place at 41 Atlanta-area hospitals between 1993 and 2004. The children, who ranged from ages 5 to 17, had been seen in a hospital emergency room for asthma or wheezing.
The research team also gathered data from the Study of Particles and Health in Atlanta to assess daily air quality and the presence of 10 different pollutants from traffic sources and ground-level ozone, a form of oxygen that is created when organic compounds, like fossil fuels, mix with nitrogen oxide and sunlight.
The study showed that ozone was strongly associated with an increase in pediatric emergency room visits due to asthma, especially between the months of May and October. There was also evidence of a dose-response relationship, meaning the greater the ozone exposure, the greater the likelihood of an asthma-related emergency room visit. This association was observed beginning with concentrations as low as 30 parts per billion.
When analyzing all of the pollutants together, the researchers found that ozone and primary pollutants from traffic were independently associated with pediatric asthma hospitalizations.
The researchers also reported that emergency room visits for pediatric asthma increased by 60% during the colder months, a factor that is not surprising given that viral respiratory infections occur more frequently during the winter and can worsen asthma. However, the association between pollution and increased emergency room visits held even after taking seasonal differences into account.
Pollution's Impact on Public Health
The findings were released just in time for Earth Day, a worldwide effort commemorated on April 22 and created to rally communities and individuals toward improving environmental standards. The study results were published on the American Thoracic Society's web site ahead of the print edition of the American Journal of Respiratory and Critical Care Medicine.
"Characterizing the associations between ambient air pollutants and pediatric asthma exacerbations, particularly with respect to the chemical composition of particulate matter, can help us better understand the impact of these different components and can help to inform public health policy decisions," writes study researcher Matthew J. Strickland, PhD, MPH, assistant professor of environmental health.
Pollution is known to worsen asthma symptoms, but researchers have been trying to discern which pollutants exacerbate asthma and which pollutants are present when pediatric emergency room visits for asthma increase.
Children may be more vulnerable during the summer because they are outside more often, the researchers note. Another explanation may be an "unidentified synergism between the pollutant and a meteorological or physical factor."
Ozone concentrations in urban areas, including Atlanta, frequently exceed Environmental Protection Agency (EPA) standards.
The findings, Strickland said, reinforce "the need for continued evaluation of the EPA's National Ambient Air Quality Standards to ensure that the standards are sufficient to protect susceptible individuals."