Monitoring of occupational exposure to cyclohexanone by diffusive sampling and urinalysis

The present study was initiated in order to identify the best marker of occupational exposure to cyclohexanone among cyclohexanone and its metabolites in urine. To examine if diffusive samplers are applicable to personal monitoring of exposure to cyclohexanone in workroom air, the performance of carbon cloth to adsorb cyclohexanone in air was studied by experimental exposure of the cloth to cyclohexanone at 5, 10, 25 or 50 ppm (i.e. 20, 40, 100 or 200 mg m-3) for up to 8 h. Cyclohexanone in the exposed cloth was extracted with carbon disulphide followed by gas chromatographic (GC) analysis. The cloth adsorbed cyclohexanone in proportion to the concentration (up to 50 ppm) and the duration (up to 8 h), and responded quantitatively to a 15 min exposure at 100 ppm. In a field survey, end-of-shift urine samples were collected from 24 factory workers occupationally exposed to cyclohexanone (up to 9 ppm) in combination with toluene and other solvents. Urine samples were also collected from 10 subjects with no occupational exposure to solvents. The urine samples were treated with acid or an enzyme preparation for hydrolysis, and extracted with dichloromethane or ethyl acetate. The extracts were analysed by GC for cyclohexanone, cyclohexanol, and trans- and cis-isomers of 1,2- and 1,4-cyclohexanediol. Both cyclohexanol and trans-1,2-cyclohexanediol in urine correlated significantly with time-weighted average intensity of exposure to cyclohexanone. Although trans -1,4-isomer was also excreted, its quantitative relation with cyclohexanone exposure could not be established, because the solvent extraction rate was low and unstable. Excretion of cis-isomers was not confirmed. The two analytes, cyclohexanol and trans-1,2-cyclohexanediol, appeared to be equally valid as exposure markers, but the latter may be superior to the former in the sense that it is sensitive enough to separate the exposed from the non-exposed at 1 ppm or less cyclohexanone exposure.