138 Interpretation of Occupational Biomonitoring Data of 1,3-Butadiene Exposure in the Form of Urinary Markers and Estimation of Urinary Half-Lives

Abstract

Abstract 1,3-Butadiene (BD) is classified as a human carcinogen and occupational exposure should be minimized in industrial installations. During the clean-up and repair of a storage tank that contained BD-contaminated sludge, the effectiveness of personal protection was checked with urinary biomonitoring of 1,2-dihydroxy-4-(N-acetylcysteinyl)-butane (DHBMA) and isomers of hydroxy-1-(N-acetylcysteinyl)-3-butene (MHBMA), biomarkers of recent BD exposure. Correlations exist between airborne BD shift exposure and end-of-shift urinary concentrations. 65 workers involved in the tank operation provided repeat urine samples before and after the shift across consecutive days for a total of 1286 samples. Inhalation exposure monitoring was not conducted as the workers used respiratory protective equipment. Different conclusions emerged from the samples regarding limit value exceedance for the two biomarkers. This large, unique dataset was investigated for patterns and apparent urinary half-lives of DHBMA and MHBMA not published yet in the scientific literature. The pattern across consecutive days for DHBMA was consistent with a low-level exposure, well below the exposure limit of 1 ppm (8-hour average), with a small increase of the body burden, whereas the pattern for MHBMA remained uninterpretable. Using a sub-set of the data, the urinary half-lives were estimated at 18.9 ± 2.6 hr (MHBMA) and 11.1 ± 3.4 hr (DHBMA). DHBMA would be the preferred biomarker to apply in situations when it is known that exposure to BD might occur to check whether protective measures are sufficient.