A simple HPLC method to determine urinary phenylmercapturic acid and its application to gasoline station attendants to biomonitor occupational exposure to benzene at less than 1 ppm

The objective of this study was to establish a hand-saving method to measur e phenylmercapturic acid (PMA) and to examine urinary PMA as a marker of oc cupational exposure to benzene at levels less than 1 ppm. A simple HPLC met hod was developed to analyse PMA by monitoring absorption at 195 nm of the effluent from an ODS-3 column with acetonitrile-methanol-perchloric acid-wa ter as a mobile phase. The detection limit of the method was 0.2 mug l(-1) with sufficient reproducibility. The method was applied to end-of-shift uri ne samples from 70 gasoline station attendants exposed to up to 107 ppb ben zene, and 20 non-exposed controls of both sexes. Time-weighted average (TWA ) exposure to benzene was measured by diffusive sampling. A regression anal ysis was applied to examine the quantitative relationship between the inten sity of exposure to benzene and PMA in the end-of-shift urine samples. Mult iple regression analysis showed no effects of age, sex, smoking and co-expo sure to toluene and xylenes on urinary PMA. There was a linear relationship between TWA benzene exposure and urinary PMA (r = 0.60-0.67, P < 0.01). Ba ckground PMA in urine of the non-exposed controls was low and scattering of PMA around the regression line was narrow so that those with 20 ppb benzen e exposure can be separated from the non-exposed by urinalysis for PMA. Thu s, urinary PMA is sensitive enough for biological exposure monitoring of th ose exposed to less than 1 ppm benzene.