Evaluation of exposure biomarkers in offshore workers exposed to low benzene and toluene concentrations

Purpose: Characterize ethylbenzene and xylene air concentrations, and explore the biological exposure markers (urinary t,t-muconic acid (t,t-MA) and unmetabolized toluene) among petroleum workers offshore. Offshore workers have increased health risks due to simultaneous exposures to several hydrocarbons present in crude oil. We discuss the pooled benzene exposure results from our previous and current studies and possible co-exposure interactions. Methods: BTEX air concentrations were measured during three consecutive 12-h work shifts among 10 tank workers, 15 process operators, and 18 controls. Biological samples were collected pre-shift on the first day of study and post-shift on the third day of the study. Results: The geometric mean exposure over the three work shifts were 0.02ppm benzene, 0.05ppm toluene, 0.03ppm ethylbenzene, and 0.06ppm xylene. Benzene in air was significantly correlated with unmetabolized benzene in blood (r=0.69, p<0.001) and urine (r=0.64, p<0.001), but not with urinary t,t-MA (r=0.27, p=0.20). Toluene in air was highly correlated with the internal dose of toluene in both blood (r=0.70, p<0.001) and urine (r=0.73, p