Co-exposure to heat and noise on workers' health: evidence from a large-scale cross-sectional surveillance study in China.

OBJECTIVES: This study aimed to investigate the synergistic effects of co-exposure to occupational heat and noise on multi-system health outcomes among Chinese workers, and to examine the mediating role of systemic inflammation, indicated by white blood cell (WBC) count. METHODS: A cross-sectional analysis was conducted using data from the Fujian Workplace Occupational Hazards Comprehensive Surveillance Program (2020-2022), encompassing 10,275 workers from the manufacturing, petrochemical, mining, and construction industries. Multivariate logistic regression, relative excess risk due to interaction (RERI), random forest with SHAP values, and mediation analysis were used to explore interaction effects and mediating pathways. RESULTS: Co-exposure to heat and noise in the workplace was associated with increased risks of hypertension (OR = 1.94, 95%CI:1.61-2.36; RERI = 0.26, P interaction <0.001) and abnormal ECG (OR = 1.81, 95%CI:1.48-2.12; RERI = 0.16, P interaction <0.001), indicating synergistic effects beyond individual exposures. WBC partially mediated the effects of occupational heat and noise exposure on hypertension (heat: 9.2%; noise: 7.4%; co-exposure: 15.3%), liver dysfunction (heat: 5.4%; noise: 13.2%; co-exposure: 11.5%), and abnormal ECG findings (heat: 7.0%; noise: 6.4%; co-exposure: 8.7%). Machine learning models further confirmed that interaction between heat and noise was a stronger predictor of adverse health outcomes than either exposure alone. CONCLUSION: Co-exposure to occupational heat and noise significantly exacerbates health risks across multiple organ systems, with systemic inflammation playing a partial mediating role. These findings highlight the importance of integrated occupational hazard assessments and targeted interventions that consider multiple concurrent occupational hazards.