Changes in the acute response of respiratory diseases to PM2.5 in New York State from 2005 to 2016.

Prior studies reported that exposure to increased concentrations of fine particulate matter (PM2.5) were associated with increased rates of hospitalization and emergency department (ED) visits for asthma and chronic obstructive pulmonary disease (COPD). In this study, rates were examined from 2005 to 2016 using a case-crossover design to ascertain if there have been changes in the rates per unit mass exposure given substantial reductions in PM2.5 concentration and changes in its composition. PM2.5 concentrations were reduced through a combination of policies designed to improve air quality and economic drivers, including the 2008 economic recession and shifts in the relative costs of coal and natural gas. The study period was split into three periods reflecting that much of the emissions changes occurred between 2008 and 2013. Thus, the three periods were defined as: BEFORE (2005 to 2007), DURING (2008-2013), and AFTER (2014-2016). In general, the number of hospitalizations and ED visits declined with the decreased concentration of PM2.5. However, the rate of COPD hospitalizations and asthma ED visits associated with each interquartile range increase in ambient PM2.5 concentration was larger in the AFTER period than the DURING and BEFORE periods. For example, each 6.8 μg/m3 increase in PM2.5 on the same day was associated with 0.4% (0.0%, 0.8%), 0.3% (-0.2%, 0.7%), and 2.7% (1.9%, 3.5) increases in the rate of asthma emergency department visits in the BEFORE, DURING, and AFTER periods, respectively, suggesting the same mass concentration of PM2.5 was more toxic in the AFTER period.