The 3-year average concentrations of PM2.5 and its constituents (nitrate [NO3-], sulfate [SO42-], ammonium [NH4+], organic matter [OM], and black carbon [BC]) were estimated using a series of machine-learning models. 
machine-learning models
Multivariate logistic regression and weighted quantile sum regression were used to estimate the independent and joint associations of PM2.5 constituents with MetS and their contribution to joint associations. 
multivariate logistic regression
Multivariate logistic regression and weighted quantile sum regression were used to estimate the independent and joint associations of PM2.5 constituents with MetS and their contribution to joint associations. 
weighted quantile sum regression