A novel method to determine uptake and elimination kinetics of volatile chemicals in fish

The development of an exposure system suitable for studying the uptake and elimination kinetics in fish of volatile chemicals is discussed. Static exposure of the fish is in a closed system containing water and air. Automated sampling and analysis of the air provides a concentration-time profile that is then fit to differential equations using numerical integration methods. Assumptions for the mathematical description of the system are a) instantaneous distribution of chemical between water and air, and b) a first order one-compartment model describes the kinetics of chemical in fish. Uptake and elimination rate constants in fathead minnows (Pimephales promelas) were determined for a mixture of benzene, toluene, monochlorobenzene, monobromobenzene, and 1,3-dichlorobenzene. No significant biotransformation was observed for any of the compounds. Uptake rate constants increased with increasing octanol-water partition coefficient (Kow), whereas the elimination rate constants were inversely related to Kow.