Simulation of the toxicokinetics of trichloroethylene, methylene chloride, styrene and n-hexane by a toxicokinetics/toxicodynamics model using experimental data.

The toxicokinetics/toxicodynamics (TKTD) model simulates the toxicokinetics of a chemical based on physiological data such as blood flow, tissue partition coefficients and metabolism. In this study, Andersen and Clewell's TKTD model was used with seven compartments and ten differential equations for calculating chemical balances in the compartments (Andersen and Clewell 1996, Workshop on physiologically-based pharmacokinetic/pharmacodynamic modeling and risk assessment, Aug. 5-16 at Colorado State University, U.S.A) . Using this model, the authors attempted to simulate the behavior of four chemicals: trichloroethylene, methylene chloride, styrene and n-hexane, and the results were evaluated. Simulations of the behavior of trichloroethylene taken in via inhalation and oral exposure routes were also done. The differences between simulations and measurements are due to the differences between the absorption rates of the exposure routes. By changing the absorption rates, the simulation showed agreement with the measured values. The simulations of the other three chemicals showed good results. Thus, this model is useful for simulating the behavior of chemicals for preliminary toxicity assessment.

Prediction of systemic concentrations of sensitizing compound using TKTD simulation model.

To investigate the safe handling of an industrial product, phenyl vinyl sulfone (PVS), which has an extremely high potential for dermal sensitization at low concentrations and positive mutagenicity, the maximum no-effect concentration for dermal deposits was obtained from dermal sensitization experiments. The systemic concentrations in the liver, which is considered to be a target tissue of mutation, were monitored using the TKTD (Toxico Kinetics Toxico Dynamics) model by inputting the maximum no-effect concentration of sensitization. The predicted highest concentration in the liver was compared with the no-effect level of mutation in the same tissue, which was derived from an in vitro mutagenicity study. The results showed that when this product is handled at lower concentrations, which may not induce dermal sensitization, the systemic concentrations would be lower than those causing mutation in the liver. In workplaces, conditions that prevent dermal sensitization caused by PVS could also protect against the mutagenicity of this compound.