Development of Statistical Approaches to Provide Toxicity Estimates from Exposure Data to Support Risk Assessments

"The technical objective in Phase I is to review and identify potential statistical approaches for obtaining probabilistic concentration and exposure threshold values for screening contaminants of military interest (military unique compounds, or MUCs) basedon existing laboratory-based toxicity and bioaccumulation data. The goal is to develop validated statistical approaches to determine the uncertainty, or confidence limits, surrounding exposure-based (e.g., bioaccumulation) toxicity estimates for use inecological risk assessments. These tools and approaches will enhance and further develop current ecological risk assessment techniques, which tend to focus on single threshold values derived deterministically, and typically do not provide confidenceintervals even in the case of probabilistic assessments.Following the identification, review, and application of potential statistical approaches that may be used to estimate concentration-based toxicity thresholds from existing toxicity and bioaccumulation data sets, we will evaluate the selected approaches.This will be done using chemical data sets that can support development of body-residue toxicity threshold and confidence intervals. We will compare the results of applications of the statistical approaches for the selected contaminants with the goal ofdeveloping an approach that combines the best features of existing methods. We anticipate developing an integrated framework to evalu