A new model function for continuous data sets in health risk assessment of chemicals using the benchmark dose concept

The benchmark dose concept is an alternative way to calculate acceptable daily intakes or other low-risk limits of exposure for nongenotoxic compounds. An effective dose that corresponds to a specific change of effect/response, e.g., 10%, over background, on a given model is calculated and a benchmark dose which is the lower confidence bound for the effective dose can be estimated. One problem with this method is that it has not been possible to model "S"-shaped curves for continuous data with the existing commercial computer programs. We present a new mathematical model for continuous data, which can form S-shaped curves. For a number of data sets on the toxicity of trichloroethene, the introduction of this new function significantly increased the possibilities to model continuous data. A new computer package has also been developed to improve and simplify the calculations of benchmark doses.