New research by George Mason University found that exposure to certain air pollutants is linked to increased emergency department (ED) visits for respiratory and cardiovascular diseases.

Mason Assistant Professor of Global and Community Health Dr. Jenna Krall led the research with colleagues from Emory University, Georgia Institute of Technology, and the University of Pittsburgh. They found that exposure to pollutants such as ground-level ozone and nitrogen oxides, which are created from burning fossil fuels, led to increased ED visits. The study is published in the journal Environment International.

We estimated associations between twelve ambient air pollutants of both primary (e.g. nitrogen oxides) and secondary (e.g. ozone and sulfate) origin and cardiorespiratory emergency department (ED) visits for 8 specific outcomes in five U.S. cities including Atlanta, GA; Birmingham, AL; Dallas, TX; Pittsburgh, PA; St. Louis, MO.

For each city, we fitted overdispersed Poisson time-series models to estimate associations between each pollutant and specific outcome. To estimate multicity and posterior city-specific associations, we developed a Bayesian multicity multi-outcome (MCM) model that pools information across cities using data from all specific outcomes. We fitted single pollutant models as well as models with multipollutant components using a two-stage chemical mixtures approach.

Posterior city-specific associations from the MCM models were somewhat attenuated, with smaller standard errors, compared to associations from time-series regression models. We found positive associations of both primary and secondary pollutants with respiratory disease ED visits. There was some indication that primary pollutants, particularly nitrogen oxides, were also associated with cardiovascular disease ED visits.

—Krall et al.

We found that primary pollutants—those that are emitted directly from a source, such as car exhaust—were associated with ED visits for cardiovascular and respiratory diseases. Additionally, secondary pollutants—those that are formed through chemical reactions in the air—were linked to ED visits for respiratory diseases.

—Dr. Krall

While most past studies were conducted on a single-city level, this study looked at pollution across five cities: Atlanta, Birmingham, Dallas, Pittsburgh, and St. Louis. The researchers analyzed the associations between cardiorespiratory ED visits and twelve major air pollutants to examine short-term changes in health as pollution varies on a daily basis.

Estimated relative risks of respiratory emergency department visits and 95% posterior intervals associated with an interquartile (IQR) increase in pollutant for both the average across cities and posterior mean estimates for each city based on the multicity multi-outcome (MCM) model. Pollutants are roughly ordered according to primary and secondary pollution, separated by a vertical line. Krall et al.

This is also one of first multicity studies to look at multiple air pollutants, including gases and particles, and multiple causes of ED visits, such as asthma and stroke. It is a larger and more comprehensive study than previous work that has commonly looked at one pollutant and multiple health outcomes, or multiple pollutants and one health outcome.

Down the line, this research has implications for how we think about future pollution regulations because the way we regulate pollutants might differ between primary and secondary pollution.

—Dr. Krall

Resources

• Jenna R. Krall, Howard H. Chang, Lance A. Waller, James A. Mulholland, Andrea Winquist, Evelyn O. Talbott, Judith R. Rager, Paige E. Tolbert, Stefanie Ebelt Sarnat (2018) “A multicity study of air pollution and cardiorespiratory emergency department visits: Comparing approaches for combining estimates across cities,” Environment International, Volume 120, Pages 312-320 doi: 10.1016/j.envint.2018.07.033