Associations of occupational heat exposure with dyslipidemia among petrochemical workers: insights from a 9-year longitudinal study

This study aims to explore the associations between occupational heat exposure and dyslipidemia among petrochemical workers, to evaluate associations in two-exposure models that include other occupational hazards, and to examine subgroup-specific patterns. A total of 30,847 occupational health examination records were collected from two petrochemical plants in Fujian Province between 2013 and 2021. The dataset included occupational exposure information and serum lipid levels (total cholesterol [TC], low-density lipoprotein cholesterol [LDL-C], high-density lipoprotein cholesterol [HDL-C], triglycerides [TG]). Generalized estimating equations (GEE) models were used to analyze the associations of occupational heat exposure with dyslipidemia and its subtypes. Sensitivity analyses and lagged exposure analyses were further performed to assess the potential influence of the healthy worker effect. In the single-exposure models, most occupational hazards showed significant inverse associations with dyslipidemia. In the two-exposure models, heat exposure was positively associated with high TC after additionally accounting for gasoline (incidence rate ratio, IRR = 1.267, 95% CI : 1.117–1.437) or H₂S (IRR = 1.324, 95% CI : 1.166–1.505). In stratified analyses, these positive associations were more evident among females (heat-gasoline model: IRR = 2.240, 95% CI : 1.639–3.062; heat-H₂S model: IRR = 2.347, 95% CI : 1.736–3.173) and workers aged ≥ 35 years (heat-gasoline model: IRR = 1.317, 95% CI : 1.158–1.497; heat-H 2 S model: IRR = 1.385, 95% CI : 1.215–1.578). Sensitivity analyses showed that the inverse association with high TG was more pronounced among workers with ≥ 5 years of employment (IRR = 0.82, 95% CI : 0.75–0.89) than among those with < 5 years (IRR = 0.91, 95% CI : 0.84–0.98). In lagged analyses, the inverse association between heat exposure and high TC was attenuated and no longer significant (IRR = 0.945, 95% CI : 0.817–1.092), whereas the inverse association with high TG remained significant (IRR = 0.883, 95% CI : 0.818–0.954). The inverse association between occupational heat exposure and dyslipidemia in the single-exposure models may be partly attributable to the healthy worker effect. In two-exposure models additionally accounting for gasoline or H₂S, heat exposure was positively associated with elevated TC, whereas subgroup-specific and lagged analyses indicated that these associations should be interpreted cautiously as exploratory.