Cardiovascular Emergency Hospitalization Risks of PM_2.5 Transition Metals: A Time-Stratified Case-Crossover Study

PM_2.5 pollution poses significant health risks in urban areas, yet the specific cardiovascular impacts of its hazardous components, especially transition metals, remain insufficiently understood. This study evaluated the associations of PM_2.5 components on acute myocardial infarction (AMI) and acute aortic dissections (AAD) emergency hospitalizations (n = 9985) using a time-stratified case-crossover between 2017 and 2023 in Xiamen, China. We collected comprehensive data on daily air pollutants, PM_2.5 components (water-soluble ions, carbon components, metals, and other elements), and meteorological variables. Conditional logistic regressions were used to estimate odds ratios (OR) per the interquartile range (IQR) of exposures. Our finding reveals significant short-term associations of exposures to air pollutants and PM_2.5 components with increased cardiovascular emergency hospitalizations. The strongest associations were observed between cumulative 3-day lagged (lag 0-3) PM_2.5 transition metals including Mn [odds ratio, OR = 1.106 (95% CI: 1.032-1.186)], Fe [OR = 1.078, (95% CI: 1.015-1.145)], V [OR = 1.117 (95% CI: 1.024-1.219)], and Zn [OR = 1.08, (95% CI: 1.005-1.161)] exposure with AMI. These associations were stronger among older (age >65 years), male patients, and during colder seasons. Our study highlights the underexplored subacute cardiovascular risks of PM_2.5 transition metals, underscoring the need to integrate them into urban air quality management to promote environmental sustainability.