BACKGROUND: Pairwise associations among fine particulate matter (PM METHODS: We included 1,459 participants from the China Multi-Ethnic Cohort between May 2018 and September 2019. CVD was identified using ICD-10 codes based on hospital surveillance system. PM RESULTS: Among all the participants, 204 (14.0%) had developed CVD during a 5,501 person-year follow-up (median, 3.8 years). The ACE, Chao1, and Obs indexes positively mediated the associations of PM CONCLUSION: Three α-indexes (ACE, Chao1, and Obs) and the Pasteurella positively mediated the association between PM