Liver changes in workers at an oil refinery and in a reference population in the state of Bahia, Brazil

Objective. To determine the prevalence of liver changes in workers at an oil refinery located in the state of Bahia, Brazil, as compared to a reference population with no occupational exposure to chemical products, and to describe the factors associated with the observed differences in prevalence. Methods. We studied workers at the refinery and at the company's central management office located in the city of Salvador, which is the state capital. Blood samples of 692 refinery workers and 377 workers from the reference population were analyzed. Cases were defined as individuals presenting high serum levels of both gammaglutarnyltransferase (GGT) and alanine aminotransferase (ALT) (GGT > 50 U/L for males and > 32 U/L for females; ALT > 50 U/U. Data were collected on age, sex, weight, height, years working for the company, use of alcohol, smoking habits, physical exercise, occupational exposure to chemical products, use of personal safety equipment, and medical history of hepatitis, jaundice, and obesity. Results. The prevalence of liver changes among refinery workers was 15.3% (95% Cl: 12.5 to 18.1), vs. 3.8% (95% Cl: 1,8 to 5,8) in the reference population. According to multiple logistic regression analysis, the prevalence of liver changes among refinery workers was 3.56 times greater (95% Cl: 1,99 to 6,38) than in the reference population, regardless of the presence of other relevant co-variables, such as obesity, exercise, smoking, and alcohol consumption. Conclusions. These results suggest that occupational exposure may play a major role in the development of liver changes among workers at the oil refinery where the study was carried out.