The distribution and pharmacokinetics of styrene monomer in rats by the pulmonary route

Exposures (5 hr) of individual rats to atmospheres having styrene concentrations of from 50 to 2,000 ppm yield uptake blood profiles which show a continued and increasing absorption of styrene, proportional to the styrene atmospheric concentration, over the entire absorption period. Post-exposure elimination follows a dose-dependent two compartment model, similar to that observed after I.V. administration, although the initial stage of the elimination is more rapid and the terminal stage much slower than is observed in the I.V. case. A two-compartment pharmacokinetic model, with zeroth-order input, is proposed to interpret the uptake kinetics. Tissue concentrations of styrene in the heart, liver, lung, kidney, spleen, brain and perirenal fat show a different pattern of distribution as the dose increases. At all exposure concentrations the concentration of styrene in the perirenal fat is ten times that in any organ. At the lowest exposure concentration the kidney registered the highest concentration while a higher level of styrene is found in the liver, brain and kidney as the exposure level increases and for these tissues the concentration of styrene is always greater than that in the blood.