Urinary methylchloroform rather than urinary metabolites as an indicator of occupational exposure to methylchloroform

In order to compare methylchloroform (MC, or 1,1,1-trichloroethane) per se and its metabolites in urine as indicators of occupational exposure to this solvent, 50 male solvent workers were studied in the second half of a working week to evaluate the exposure-excretion relationship. The time-weighted average intensity of solvent exposure of individuals during an 8-h shift was monitored by personal diffusive sampling. Urine samples were collected near the end of the shift and were analyzed for MC and its metabolites [i.e., trichloroacetic acid (TCA), trichloroethanol (TCE) and total trichloro-compounds (TTC; the sum of TCA and TCE)] by head-space gas chromatography. MC per se, TCA, TCE, and TTC in urine correlated significantly (P < 0.01) with MC in ambient air, and among the four the correlation coefficient was highest for MC. The same result were obtained by multiple regression analysis in which ambient air MC was taken as the dependent variable and either the three indicators urinary MC, TCA, and TCE or the two indicators urinary MC and TTC were taken as independent variables. Taking the specificity and selectivity of the analyte as well as the simple and hazardous chemical-free procedure of analysis into consideration, it is concluded that MC is the analyte of choice as an indicator of occupational exposure to MC, when urine is selected as a specimen available by noninvasive sampling.