Urinary thioether output as an index of occupational chemical exposure in petroleum retailers.

Petroleum is a complex mixture of lipophilic chemicals, some of which are likely to be substrates for the microsomal mixed function oxygenases. Petroleum retailers, by virtue of their occupational exposure potential, are a group likely to receive relatively heavy exposure to petroleum products in comparison with the general public. Urinary thioether output may provide a simple, non-invasive technique for identifying occupational chemical exposure."2 The technique exploits the fact that conjugation with glutathione, followed by urinary elimination as mercapturates, is a significant metabolic clearance pathway for electrophilic chemicals and, in particular, for putatively toxic metabolites of the microsomal mixed function oxygenase system. Raised thioether output has been confirmed for several occupations associated with potential exposure to such chemicals.36 Induction of the microsomal oxygenases is a common response to the ingestion of lipophilic chemicals. Since hepatic microsomes from rats exposed to petroleum vapours were found to have induced activity towards a range of cytochrome p450 substrates,7 it was reasonable to interpret the faster clearance of antipyrine in a cohort of petroleum retailers7 to result from occupational exposure to petroleum, although it was not possible to confirm exposure more directly using indices based on petroleum components such as benzene or lead and shown by others8 9 to be sensitive to petroleum exposure. This study was undertaken to assess the utility of the urinary thioether technique to detect occupational chemical exposure in petroleum retailers. Since attendant operated pumps have been supplanted in many outlets by self-service pumps, it was of some interest to determine whether this difference in retailing practice was reflected in the occupational exposure patterns.