Liver function assessment in workers exposed to vinyl chloride
Objective: To investigate liver function in vinyl chloride workers and assess its relation with current/past occupational exposure to vinyl chloride monomer (VCM). Methods: A medical examination including the execution of liver function tests (LFTs) and liver ultrasonography was executed in a group of 757 workers with a long-standing service in the production of VCM/polyvinylchloride (PVC). Cumulative and maximum VCM exposures were calculated. History of viral hepatitis and alcohol intake were carefully investigated. Regression analysis explored the association between abnormal LFTs and a group of possible determinants (VCM cumulative and maximum exposure, BMI, age, history of viral hepatitis, alcohol and triglyceride levels). Also, synergistic effect between VCM and a history of hepatitis was analysed, as well as the possible association between VCM exposure and aspartate aminotransferase/alanine amino transferase (AST/ALT) ratio >1. Distribution of abnormal LFTs was also assessed in relation to the results provided by liver ultrasonography. Results: The most frequently abnormal serum parameters were, in decreasing order: total cholesterol (27.3%), triglycerides (12.2%), total bilirubin (9.1%), gamma glutamil transpeptidase (GGT; 9.0%) and ALT (8.2%). The AST/ALT ratio >1 was present in 28.1% of workers. Abnormal LFTs were not found to be associated with current or past VCM exposure. High ALT resulted positively associated with BMI, AST with alcohol intake, GGT with alcohol intake and triglycerides. No synergistic effect on LFTs of exposure to VCM and a history of hepatitis was observed. The AST/ALT ratio >1 was not found to be associated with VCM exposure. The prevalence of abnormal LFTs was higher in case of liver steatosis (ALT) or periportal fibrosis (GGT), but not in case of pure hepatomegaly, as documented by ultrasonography. Conclusions: Liver function assessment only including LFTs is not able to detect VCM-induced liver damage, but reveals alterations due to non-occupational factors, such as dietary and/or metabolic disfunctions. The LFTs are however of importance to detect conditions that could recommend avoidance of exposure to VCM and are useful for medical counselling and health promotion purposes.