Prevalence of nonalcoholic fatty liver disease in workers of an automobile enterprise: the role of low-dose heavy metal exposure and related factors of the disease

Background Some studies have found that exposure to heavy metals significantly increases the risk of nonalcoholic fatty liver disease (NAFLD), and welding operators in automobile manufacturing enterprises are exposed to heavy metals in the working environment.

Objective To analyze the prevalence and related factors of NAFLD in workers of an automobile company in Guangzhou.

Methods From January 1 of 2023 to December 31 of 2023, 5463 workers of an automobile company in Guangzhou who participated in the physical examination in the Occupational Health Surveillance Centre of Guangzhou Occupational Disease Prevention and Treatment Hospital were selected as research subjects. The general data, laboratory examinations, B-ultrasound examinations, and other data of the subjects were obtained through the physical examination system. The exposed occupational hazards were identified based on the workplace hazard surveillance report provided by the automotive company. Logistic regression was used to analyze potential influencing factors of NAFLD, and stratified analysis was used to adjust confounding factors according to the stepwise model to evaluate the relationship between exposure to manganese and its inorganic compounds and NAFLD.

Results A total of 2129 cases (38.97%) were reported positive NAFLD. The results of logistic regression analysis showed that women had a lower risk of NAFLD (OR=0.40, 95%CI: 0.25, 0.64), while age > 25 years old (OR=1.49, 95%CI: 1.39, 1.60), body mass index (BMI) ≥24 kg·m⁻² (OR=7.54, 95%CI: 6.46, 8.79), and elevated alanine aminotransferase (ALT) (OR=4.87, 95%CI: 3.73, 6.36), γ-glutamyl transpeptidase (γ-GGT) (OR=1.54, 95%CI: 1.17, 2.02), triglyceride (TG) (OR=3.47, 95%CI: 2.92, 4.14), and fasting blood glucose (OR=1.70, 95%CI: 1.32, 2.20) associated with a higher risk of NAFLD. NAFLD was positive in 39.40% of heavy metal exposed workers (701/1779). NAFLD was positive in 45.19% of workers exposed to manganese and its inorganic compounds (169/374), and among workers over 34 years old, exposure to manganese and its inorganic compounds (OR=1.79, 95%CI: 1.07, 2.97) significantly increased the prevalence of NAFLD.

Conclusion The association between heavy metal exposure and NAFLD in workers of an automobile enterprise in Guangzhou is not significant, but age and gender are related to the prevalence of NAFLD. BMI, ALT, γ-GGT, TG, and fasting blood glucose are positively correlated with the prevalence of NAFLD. Exposure to manganese and its inorganic compounds in welding workers of the automobile enterprise is associated with elevated risk of the disease, and the prevalence of NAFLD is significantly increased in workers over 34 years old.