Excretion of metabolites of styrene (dose: 2.2 mmol/kg i.p.) in 24-h urine was suppressed when rats were coinjected intraperitoneally with either toluene or trichloroethylene (dose: 2.2--11.0 mmol/kg) in addition to styrene, while a coinjection of n-hexane, ethyl acetate, methylchloroform, or acetone at an equimolar dose was ineffective in all cases. Suppressive effects of toluene and trichloroethylene were further confirmed by 6-h vapor exposure to (a) 0 to 1,300 ppm of toluene in addition to 150--170 ppm of styrene and (b) 0 to 4,000 ppm of trichloroethylene together with 100 or 150 ppm of styrene. The relationship between the amounts of three metabolites (i.e., phenylglyoxylic, mandelic and hippuric acids) in urine and styrene concentration in air was also determined.

Key terms coexposure; metabolic interaction; organic solvent; styrene; toluene; trichloroethylene