Joint Effects of Ambient Air Pollutants on Pediatric Asthma Emergency Department Visits in Atlanta, 1998-2004

• Authors: Andrea Winquist, Emory University; Ellen Kirrane, Environmental Protection Agency; Mitchel Klein, Emory University; Matthew Strickland, Emory University; Lyndsey Darrow, Emory University; Stefanie Sarnat, Emory University; Katherine Gass, Emory University; James Mulholland, Georgia Institute of Technology; Armistead Russell, Georgia Institute of Technology; Paige Tolbert, Emory University
• Journal Title: Epidemiology
• Volume: Volume 25, Number 5
• Publisher: Lippincott, Williams & Wilkins | 2014-09-01, Pages 666-673
• Type of Work: Article | Post-print: After Peer Review
• Publisher DOI: http://doi.org/10.1097/EDE.0000000000000146
• Subjects: Health Sciences, Epidemiology; Health Sciences, Public Health; Environmental Sciences
• Keywords: Science & Technology; Life Sciences & Biomedicine; Public, Environmental & Occupational Health; PUBLIC, ENVIRONMENTAL & OCCUPATIONAL HEALTH, SCI; CUMULATIVE RISK-ASSESSMENT; SHORT-TERM ASSOCIATIONS; TIME-SERIES HEALTH; SOURCE-APPORTIONMENT; GASEOUS-POLLUTANTS; MEASUREMENT ERROR; DAILY MORTALITY; POLLUTION; QUALITY; MULTIPOLLUTANT

Abstract

BACKGROUND: Because ambient air pollution exposure occurs as mixtures, consideration of joint effects of multiple pollutants may advance our understanding of the health effects of air pollution. METHODS: We assessed the joint effect of air pollutants on pediatric asthma emergency department visits in Atlanta during 1998-2004. We selected combinations of pollutants that were representative of oxidant gases and secondary, traffic, power plant, and criteria pollutants, constructed using combinations of criteria pollutants and fine particulate matter (PM2.5) components. Joint effects were assessed using multipollutant Poisson generalized linear models controlling for time trends, meteorology, and daily nonasthma upper respiratory emergency department visit counts. Rate ratios (RRs) were calculated for the combined effect of an interquartile range increment in each pollutant's concentration. RESULTS: Increases in all of the selected pollutant combinations were associated with increases in warm-season pediatric asthma emergency department visits (eg, joint-effect RR = 1.13 [95% confidence interval = 1.06-1.21] for criteria pollutants, including ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide, and PM2.5). Cold-season joint effects from models without nonlinear effects were generally weaker than warm-season effects. Joint-effect estimates from multipollutant models were often smaller than estimates based on single-pollutant models, due to control for confounding. Compared with models without interactions, joint-effect estimates from models including first-order pollutant interactions were largely similar. There was evidence of nonlinear cold-season effects. CONCLUSIONS: Our analyses illustrate how consideration of joint effects can add to our understanding of health effects of multipollutant exposures and also illustrate some of the complexities involved in calculating and interpreting joint effects of multiple pollutants. Copyright © 2014 by Lippincott Williams & Wilkins.