The Importance of Sampling Time and Coexposure to Acetone in the Biological Monitoring of Styrene-Exposed Workers

Abstract

Forty-four workers exposed to styrene and acetone in the fiberglass industry were monitored on Monday and Thursday for 8 hours using passive dosimeters. The charcoal discs of the passive dosimeters were analyzed by gas chromatography. The 8-hour time-weighted average (TWA) exposure values ranged from 10 to 522 and 14 to 1581 mg/m³ on Monday and from 9 to 423 and 10 to 579 on Thursday for styrene and acetone, respectively. Urine samples were collected at the end of the work shift and before the start of the work shift the next morning (Tuesday and Friday). Mandelic acid and phenylglyoxylic acid were measured in the urine using a high pressure liquid chromatography method; values were expressed in milligrams/gram creatinine. Styrene TWA exposure values significantly correlated with the sum of metabolites at the end of the workday (r = 0.60 on Monday and r = 0.77 on Thursday) and also the next morning (r = 0.87 on Tuesday and r = 0.84 on Friday). Mandelic acid was always correlated with exposure better than phenylglyoxylic acid. A calculated styrene exposure level of 213 mg/m³ (American Conference of Governmental Industrial Hygienists threshold limit value) was associated with an excretion of metabolites (mandelic acid + phenylglyoxylic acid) higher on Thursday (921 mg/g creatinine) than on Monday (706 mg/g creatinine). The same observation was made on Friday (423 mg/g creatinine) as compared with Tuesday (315 mg/g creatinine). In conclusion, the threshold limit value of styrene was associated with different values of metabolites at the beginning and at the end of the workweek, and we must take this into account in establishing biological exposure indices. Moreover, our data show that the excretion of mandelic acid and phenylglyoxylic acid is not modified by simultaneous exposure of the workers to acetone.