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

Background: Fine 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. Objective: To identify the specific size ranges that dominate the effects of particulate matter on AMI onset. Methods: We conducted a time-series study in Shanghai, China from January 2014 to December 2018. We evaluated particle size distribution of 0.01 mu m to 25 mu m 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. Results: We identified a total 014720 AMI emergency hospitalizations. PM2.5 was significantly associated with increased AMI risk on the concurrent day. The associations were significant only for PNC < 03 mu m. For an IQR increase of PNCs for size ranges 0.01-0.03 mu m, 0.03-0.05 mu m, 0.05-0.10 mu m and 0.10-0.30 mu m, 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 mu m 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. Conclusions: This epidemiological investigation suggested that ultrafine particles, especially those <0.05 mu m may be mainly responsible for the acute AMI risk induced by PM2.5. (C) 2020 Elsevier B.V. All rights reserved.