Short-term exposure to ambient fine particulate matter constituents and myocardial infarction mortality

Short-term ambient fine particulate matter (PM_2.5) exposure has been related to an increased risk of myocardial infarction (MI) death, but which PM_2.5 constituents are associated with MI death and to what extent remain unclear. We aimed to explore the associations of short-term exposure to PM_2.5 constituents with MI death and evaluate excess mortality. We conducted a time-stratified case-crossover study on 237,492 MI decedents in Jiangsu province, China during 2015-2021. Utilizing a validated PM_2.5 constituents grid dataset at 1 km spatial resolution, we estimated black carbon (BC), organic carbon (OC), sulfate (SO₄^2-), nitrate (NO₃^-), ammonium (NH₄⁺), and chloride (Cl^-) exposure by extracting daily concentrations grounding on the home address of each subject. We employed conditional logistic regression models to evaluate the exposure-response relationship between PM_2.5 constituents and MI death. Overall, per interquartile range (IQR) increase of BC (lag 06-day; IQR: 1.75 μg/m³) and SO₄^2- (lag 04-day; IQR: 5.06 μg/m³) exposures were significantly associated with a 3.91% and 2.94% increase in odds of MI death, respectively, and no significant departure from linearity was identified in the exposure-response curves for BC and SO₄^2-. If BC and SO₄^2- exposures were reduced to theoretical minimal risk exposure concentration (0.89 μg/m³ and 1.51 μg/m³), an estimate of 4.55% and 4.80% MI deaths would be avoided, respectively. We did not find robust associations of OC, NO₃^-, NH₄⁺, and Cl^- exposures with MI death. Individuals aged ≥80 years were more vulnerable to PM_2.5 constituent exposures in MI death (p for difference <0.05). In conclusion, short-term exposure to PM_2.5-bound BC and SO₄^2- was significantly associated with increased odds of MI death and resulted in extensive excess mortality, notably in older adults. Our findings emphasized the necessity of reducing toxic PM_2.5 constituent exposures to prevent deaths from MI and warranted further studies on the relative contribution of specific constituents.