The risk for acute respiratory distress syndrome (ARDS) in older adults increases with long-term exposure to particular matter smaller than 2.5 microns (PM2.5) and ozone, according to a study recently published in CHEST.

Researchers from the School of Public Health at Harvard University in Boston compiled Medicare Provider Analysis and Review inpatient data from 2000 to 2012 to gather ARDS diagnosis rates in different zip codes. Predicted PM2.5and ozone concentrations were calculated based on data collected from the US Environmental Protection Agency in these same zip codes. Covariates considered included environmental factors such as air temperature and relative humidity, proportion of different races, proportion of women, yearly income, and estimated levels of smokers in each zip code area.

After analysis of all these factors, the researchers  found that zip codes experiencing an increase of 1 µg/m³ in annual average PM2.5 and 1 ppb in annual average ozone saw rises in annual hospital admission rates for patients with ARDS at rates of 0.76% (95% CI, 0.66%-0.86%) and 0.24% (95% CI, 0.18%-0.31%), respectively. This correlation was observed even in zip codes with lower overall levels of air pollution (1.50%; 95% CI, 1.27-1.72 and 0.27%; 95% CI, 0.16-038, respectively).

Unmeasured covariates may confound these associations. In addition, the use of clinical codes in the absence of other clinical data could cause some misclassification. The source of race/ethnicity data for this study did not separate Hispanic ethnicity and racial questions. Other air pollutants, such as nitrogen dioxide, sulfur dioxide, and carbon monoxide, were not studied for this report.

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Nonetheless, this is the largest nationwide longitudinal study on air pollution as an environmental risk factor for ARDS. The researchers concluded that even in regions with low air pollution, increasing the levels of PM2.5 and ozone are associated with an increased risk for ARDS.

Reference

Rhee J, Dominici F, Zanobetti A, et al. Impact of long-term exposures to ambient PM2.5 and ozone on acute respiratory distress syndrome (ARDS) risk for older adults in the United States [published online March 26, 2019]. CHEST. doi:10.1016/j.chest.2019.03.017