Additive effects of heat and volatile organic compounds co-exposure on metabolic syndrome: evidence from petrochemical workers in China.

OBJECTIVE: To investigate the independent and joint associations of heat and volatile organic compounds (VOCs) exposure with metabolic syndrome (MetS) among petrochemical workers. METHODS: A cross-sectional study was conducted among 1140 petrochemical workers in the Quangang Petrochemical Industrial Park, China. Occupational heat and VOCs exposures were assessed following national occupational standards, and MetS was defined according to the 2020 Chinese Type 2 Diabetes Prevention and Treatment Guidelines. Multivariable logistic regression and interaction analysis using the relative excess risk due to interaction (RERI) were performed to evaluate additive associations. Machine learning models were further applied to explore the relative contributions of exposures. RESULTS: The prevalence of MetS among workers was 27.8%. After adjustment for demographic, behavioral, and occupational factors, heat exposure (OR = 1.53, 95% CI: 1.12-1.94) and VOCs exposure (OR = 1.38, 95% CI: 1.08-1.79) were both associated with higher MetS risk. Workers exposed to both heat and VOCs showed a stronger association with MetS (OR = 2.08, 95% CI: 1.32-2.96), with evidence of a positive additive interaction (RERI = 0.405, Pinteraction = 0.012). Exploratory machine-learning analyses further suggested that combined heat and VOC exposure contributed more to MetS than either exposure alone. CONCLUSIONS: Combined exposure to heat and VOCs showed evidence of a positive additive interaction in relation to MetS among petrochemical workers. These findings underscore the need for integrated occupational health strategies in heat-sensitive industries under a warming climate.