Kinetic interpretation of the exposure test for styrene.

The excretion kinetics of mandelic and phenylglyoxylic acids investigated over three subsequent days after cessation of styrene inhalation could be expressed by biphasic functions, similar for both metabolites; the half-times for the first and the second phases were 2.5 and 30 h, respectively. The possibility of styrene accumulation in exposure repeated daily was assessed by kinetic modelling; it appears negligible if measurements are based on urine samples collected at the end of the working shift. The above contention has been examined in workers exposed to styrene in the polyester industry: concentrations of styrene in air monitored continuously varied from 26 to 130 mg/m3. The relationship between styrene concentration and rate of urinary excretion of the total amount of mandelic and phenylglyoxylic acids was rectilinear and demonstrated a reasonable agreement between experimental and industrial data. The trends of concentrations within the day and week gave no indication of substantial styrene cumulation under repeated industrial exposure.