Components of particulate matter as potential risk factors for acute myocardial infarction.

Background: Particulate matter with an aerodynamic diameter of ≤2.5 µm (PM_2.5) is a heterogeneous mixture, and specific substances that affect cardiovascular events remain unknown. We aimed to examine the association of short-term exposure to PM_2.5 and its components with hospital admissions for acute myocardial infarction (AMI).

Methods: The concentrations of total PM_2.5 and its individual components were continuously measured using Aerosol Chemical Speciation Analysers. From a national-scale administrative database collected from 828 facilities in 47 prefectures across Japan from April 2017 to December 2019, we extracted AMI data for seven prefectures where these aerosol analysers were installed. The primary outcome was the relationship of PM_2.5 and its components with AMI hospitalisation. A time-stratified case-crossover analysis was conducted, and the approximate risk of AMI by pollutant concentrations was estimated using a conditional logistic regression model. In total, 44,232 patients with AMI aged 40-104 years (74.9% male) were examined.

Results: The estimated effect of an increase in the total PM_2.5 concentration is significantly associated with AMI-related hospitalisation. Upon further examination of the components of PM_2.5, black carbon has a more substantial influence on AMI development than water-soluble organic compounds, nitrate, and sulphate ions.

Conclusions: Short-term exposure to PM_2.5 is associated with an increased incidence of AMI. Future research prioritises the components of PM_2.5, with particular focus on whether a decrease in black carbon concentrations can mitigate the risk of future air quality-related AMI.