Relationship Between Exposure to Xylenes and Ethylbenzene Expressed Either in Concentration in Air and Amount of Their Metabolites Excreted in the Urine

The urinary excretion of methylhippurics, mandelic and phenylglyoxylic acids was studied in histopathological technicians (102 subjects; 14 men and 88 women) exposed to Xylol (xylenes and ethylbenzene). From each worker, the urine sample was analyzed by HPLC-UV and xylene isomers and ethylbenzene in air samples were determined by GC-FID. The mean values of time-weighted average (TWA) exposure to xylol in the Pathological Anatomy Lab were 119 +/- 49 p.p.m. (mean +/- S.D.) with a range 50-190 p.p.m. for xylene and 131 +/- 50 p.p.m. with a range 68-200 p.p.m. for ethylbenzene. There was a linear correlation between the 8-h time weighted average exposure either to xylene isomers or ethylbenzene and the concentrations of methylhippuric acids (MHA) isomers or mandelic (MA) and phenylglyoxylic acids (PGA) in urine. The r(2) value for the regression equation between total xylenes exposure and total MHA was 0.471 (positive correlation) and for the regression equation between ethylbenzene and MA + PGA was 0.950 (high positive correlation). No difference was found in the correlation between quantitative exposure and excretion in the three xylene isomers. Both MHA and MA + PGA can be used as indicators of commercial xylol exposures. So, the determination of the concentration of these metabolites in post-shift urine provides an effective means of estimating and monitoring human exposure to Xylol. Extrapolation of data from this study predicted a MHA concentration in post-shift urine of 1.27 g/g creatinine after exposure to a TWA of 100 p.p.m. of total xylenes and 0.7 g/g creatinine of MA + PGA after exposure to a TWA of 100 p.p.m. of ethylbenzene.