The Impact of Air Pollution Regulations on the Incidence of Hospitalizations and Emergency Department Visits for Respiratory Infections in New York State

Rationale: Particulate air pollution (PM) has been associated with respiratory infections. Over the past 10 years in New York State, policy initiatives targeting diesel fuel and vehicles, and industrial and power plant emissions were developed to improve air quality. These initiatives have resulted in reduced air pollutant levels, including PM2.5. We hypothesized that these policy initiatives and resultant changes in air pollution are associated with changes in the incidence of emergency department (ED) visits and hospitalizations for respiratory infections. Methods: From the Statewide Planning and Research Cooperative System (SPARCS), we retained data on all hospitalizations and ED visits alone for NY residents over age 18 living within 15 miles of the Buffalo, Rochester, Albany, Bronx, Manhattan, or Queens air quality monitoring sites. Respiratory infection included all patients with a primary diagnosis of influenza or bacterial or culture negative pneumonia. To estimate the excess rate (ER) of either inpatient or outpatient treatment for respiratory infection associated with increased ambient PM2.5 concentrations on multiple lag days (1-7 days prior to treatment), we used a time-stratified case-crossover design and conditional logistic regression analyses. We then evaluated whether the association between PM2.5 and the respiratory infection rate differed by period of NYS regulations (BEFORE=2005-2007, DURING=2008-2013, AFTER=2014-2016). Results: Interquartile range increases (IQR) in PM2.5 in the previous 6 days were associated with an increased rate of hospitalizations (ER 2.7%; 95% CI: 2.0, 3.4) and ED visits (ER 2.8%; 95% CI: 1.7, 3.9) for respiratory infections. While there was an increased ER for bacterial pneumonia hospitalizations (ER 3.7%; 95% CI: 1.2, 6.3) there was no increased ER for bacterial pneumonia ED visits (ER -0.8%; 95% CI: -7.1, 5.9). Furthermore, the increased ER for bacterial pneumonia hospitalizations associated with increased PM2.5 concentrations in the previous 6 days in the BEFORE period (ER 4.1%; 95% CI: 0.7, 7.7) was not present in the AFTER period (ER -6.9%; 95% CI: -21.1, 9.9). For culture negative pneumonia, the ER associated with increased PM was similar for hospitalizations and ED visits. No ER associated with increased PM was noted for influenza in either clinical setting. Conclusion: An excess rate of both hospitalizations and ED visits associated with increased PM was noted for all respiratory infections combined. The higher excess rate of hospitalizations for bacterial pneumonia in the period prior to regulations compared to after regulations suggests that air quality regulations may change the associations between PM and respiratory infections.