Size-fractionated particulate air pollution and myocardial infarction emergency hospitalization in Shanghai, China

Abstract

BackgroundFine particulate matter (PM2.5) air pollution has been associated with increased risks of acute myocardial infarction (AMI), but it remains unknown about the potentially differentiated effects of size-fractionated particulate matter on AMI risk. ObjectiveTo identify the specific size ranges that dominate the effects of particulate matter on AMI onset. MethodsWe conducted a time-series study in Shanghai, China from January 2014 to December 2018. We evaluated particle size distribution of 0.01 μm to 2.5 μm from an environmental supersite and AMI emergency hospitalizations from the largest cardiovascular hospital in Shanghai. We used over-dispersed generalized additive models to estimate the associations of size-fractionated particle number concentrations (PNC) with AMI and its types. ResultsWe identified a total of 4720 AMI emergency hospitalizations. PM2.5 was significantly associated with increased AMI risk on the concurrent day. The associations were significant only for PNC < 0.3 μm. For an IQR increase of PNCs for size ranges 0.01–0.03 μm, 0.03–0.05 μm, 0.05–0.10 μm and 0.10–0.30 μm, AMI hospitalizations increased by 6.68% (95% CI: 2.77%, 10.74%), 6.53% (95% CI: 2.08%, 11.17%), 5.78% (95% CI: 0.92%, 10.88%) and 5.92% (95% CI: 1.31%, 10.74%), respectively. The associations of PNC < 0.05 μm remained significant when adjusting for other air pollutants. There were consistently much stronger associations of particles with ST-segment elevation AMI than those with non-ST-segment elevation AMI. ConclusionsThis epidemiological investigation suggested that ultrafine particles, especially those <0.05 μm, may be mainly responsible for the acute AMI risk induced by PM2.5.