Forecasts of expected environmental concentrations (EEC) Require Quantitative biotransformation data. Although it is recognized that nonquantative methods may have their place in studies such as netabointe identification on pass fail degradation tests, the use of mathematical system models to forecast the EEC in typical aquatic environments requires that the rates of all important transformations (e.g., biotransformation, photolysis, etc.) be described mathematically, biotransformation rates are not suitable for (prediction because the rates are functions of conditions used in the kinetic determination on the other hand, rate constants are presumably independent of environmental factors and reproducible from site to site. Thus the mathematical formalism used to describe biotransformation should be a rate equation from which rate constants can be derived.