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Prior to the 1990's, RfDs and RfCs had been determined from no-observed-adverse-effect levels (NOAELs), which represent the highest experimental dose for which no statistically significant adverse health effects were reported or, in the absence of a NOAEL, the lowest-observed-adverse-effect levels (LOAEL). In 1995, EPA's Risk Assessment Forum published guidance on the benchmark dose (BMD) approach in the assessment of noncancer health risk (U.S.EPA, 1995) which listed several advantages of the BMD approach over use of NOAELs and LOAELs. In 1995, EPA's National Center for Environmental Assessment (NCEA) initiated a project to develop benchmark dose software to assist Agency risk assessors in deriving benchmark dose values for use in Agency risk assessments.
This latest version (2.0) contains twenty five (25) different models that are appropriate for the analysis of dichotomous (quantal) data (Gamma, Hill, Logistic, Log-Logistic, Multistage, Probit, Log-Probit, Quantal-Linear, Quantal-Quadratic, Weibull and Multistage-Cancer), continuous data (Linear, Polynomial, Power, Hill and Exponential) and nested developmental toxicology data (NLogistic, NCTR, and Rai & Van Ryzin).
Use of BMD methods involve fitting mathematical models to dose-response data and using the different results to select a BMD that is associated with a predetermined benchmark response (BMR), such as a 10% increase in the incidence of a particular lesion or a 10% decrease in body weight gain. BMDS facilitates these operations by providing simple data-management tools and an easy-to-use interface to run multiple models on the same dose-response data set.
Results from all models include a reiteration of the model formula and model run options chosen by the user, goodness-of-fit information, the BMD, and the estimate of the lower-bound confidence limit on the BMD (BMDL). Model results are presented in textual and graphical output files which can be printed or saved and incorporated into other documents.