Neighborhood-specific differences in urban air pollution levels were associated with incidence rates for asthma-related emergency department (ED) visits, researchers reported in the American Journal of Respiratory and Critical Care Medicine.
The researchers conducted a retrospective, cross-sectional, ecologic study evaluating associations between census tract-level rates of asthma-related ED visits and average ambient concentrations of particulate matter with aerodynamic diameter ≤2.5 µm (PM2.5) and ≤10 µm (PM10), nitrogen dioxide (NO2), and sulfur dioxide (SO2).
The researchers quantified excess exposure to at least 1 pollutant for Latinx or Black populations within the Austin, Texas, Metropolitan Statistical Area (MSA) and assessed the attenuation of race- and ethnicity-based incidence risk ratios (IRR) in models controlling for pollution exposure.
The analysis included populations at the census-tract level within the 5-county Austin MSA for 2016 to 2017, with 15,684 asthma-related ED visits. The overall MSA population-based incidence rate per 10,000 person-years was 84.9 in children and 27.9 in adults.
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[T]hese findings suggest that air pollution variability could contribute to within-city racial and ethnic disparity in asthma morbidity.
Average PM2.5, PM10, and SO2 concentrations were correlated with an increase in asthma-related ED visit rates in single pollutant models that controlled for socioeconomic status (SES) and housing covariates. In a multipollutant model that evaluated the 4 pollutants simultaneously, the IRR of asthma-related ED visits associated with PM10 and SO2 were attenuated but still significant in all-age and age-stratified models.
White residents generally lived in neighborhoods with lower concentrations of all 4 pollutants vs the other racial/ethnic groups. Black residents had the highest median concentrations of each pollutant, followed by Latinx residents. When SES and housing covariates were included in the analysis, PM10 and SO2 concentrations still had a significant positive association with the share of Black census-tract residents, and for PM2.5 and PM10 with the share of Latinx residents.
The proportion of Black and Latinx residents were significant predictors of census tract asthma-related ED visit rates. A 10% increase in the proportion of Black residents was associated with an IRR of 1.51 (95% CI, 1.48-1.54), and an age stratified IRR of 1.47 (95% CI, 1.43-1.52) for pediatric population-based incidence rates (PBIR) and 1.47 (95% CI, 1.42-1.51) for adult PBIR. The IRR correlated with the proportion of Latinx residents was lower (1.12; 95% CI, 1.10-1.14) in the overall population, 1.10 (95% CI, 1.08-1.13) for pediatric individuals, and 1.11 (95% CI, 1.08-1.13) for adults.
When all pollutants were included, the IRR for the proportion of Black residents was attenuated by 24% (IRR 1.39; 95% CI, 1.39-1.42), 25% (1.35; 95% CI, 1.31-1.40), and 19% (1.36; 95% Ci, 1.32-1.41) in all-ages, pediatric, and adult models, respectively. The IRR for the proportion of Latinx residents was attenuated by 32% (1.08; 95% CI, 1.06-1.1), 36% (1.07; 95% CI, 1.04-1.09), and 54% (1.06; 95% CI, 1.04-1.09) for all-ages, pediatric, and adult models, respectively.
Among several limitations, health outcome data were obtained for administrative purposes and may be affected by miscoding, and the PBIR does not differentiate between areas with a few individuals who visit the ED for asthma-related reasons many times annually and those in which many individuals visit at a lower frequency. Furthermore, individual risk factors were not controlled for, including second-hand smoke exposure.
“Because associations between census tract racial/ethnic composition and asthma-related ED visit rates are attenuated when controlling for within-city pollution variability, these findings suggest that air pollution variability could contribute to within-city racial and ethnic disparity in asthma morbidity,” the study authors stated.
