Exposure to particulate matter with aerodynamic diameter ≤2.5 μm (PM) was associated with the risk for metabolic syndrome (MetS) in the general population, but the contributions of individual PMconstituents to this association and the potential pathway between PMconstituents and MetS risk are not well elaborated. This study aimed to investigate associations between PMconstituents and MetS in general populations, relative importance of PMconstituents to and mediation effects of serum uric acid (SUA) on those associations. The 48,148 participants from a provincially representative cohort established in southwest China were included. The 3-year average concentrations of PMand its constituents (nitrate [NO], sulfate [SO], ammonium [NH], organic matter [OM], and black carbon [BC]) were estimated using a series of machine-learning models. Multivariate logistic regression and weighted quantile sum regression were used to estimate effects of independent PMconstituents on MetS and their contributions to the joint effect. Mediation analysis examined the potential mediation effects of SUA on the associations between PM constituents and MetS. Each interquartile range (IQR) increase in the concentration of PMconstituents was all positively associated with the increased MetS odds, including SO(OR = 1.15 [1.11, 1.19]]), NO(OR = 1.12 [1.08, 1.16]), NH(OR = 1.13 [1.09, 1.17]), OM (OR = 1.09 [1.06, 1.13]), and BC (OR = 1.09 [1.06, 1.13]). Their joint associations on MetS were mainly attributed to SO(weight=46.1%) and NH(44.0%). The associations of PMconstituents with abnormal MetS components were mainly attributed to NHfor elevated BP (51.6%) and reduced HDL-C (97.0%), SOfor elevated FG (68.9%), NO- for elevated TG (51.0%), and OM for elevated WC (63.0%). Percentages mediated by SUA for the associations of PMSO, NO, and BC with MetS were 13.6%, 13.1%, 10.6%, and 11.1%, respectively. Long-term exposure to PMconstituents, mainly NHand SO, was positively associated with MetS odds, partially mediated by SUA. 2.5 2.5 2.5 2.5 2.5 2.5 3 4 4 2.5 2.5 2.5 4 3 4 4 4 2.5 4 4 3 2.5, 4 3 2.5 4 4 -2-+ 2--+ 2-+ + 2-2--+ 2-
