Expert judgment of pharmaceutical and over-the-counter drugs present in recycled water for indirect potable reuse

We demonstrate the application of a novel four-step elicitation technique for generating expert predictions of the concentration of pharmaceutical and over-the-counter drugs expected to be present in recycled water used for supplementing drinking water over the next twenty years (indirect potable reuse or IPR). This work is part of a larger project that is assessing the risks of IPR projects using relative risk assessments and developing “safe” concentration levels for drugs and other non-regulated chemicals. The project is also predicting contaminants that may be of future concern based on pharmaceutical production trends and use, their fate during water reclamation treatment processes, and testing expert judgment of future exposures against these predictions. The method is a structured elicitation of expert judgment and offers an alternative to other methods for examining risks and providing transparent risk assessment where data may be lacking. In such instances as environmental health hazards with low probability and potentially catastrophic outcomes, data for risk estimates must be inferred from alternative sources such as expert opinions. These opinions are often elicited in the form of subjective confidence intervals; however the judgments are prone to cognitive biases such as overconfidence. In this study, predictions of chemical exposures are elicited by means of an expert judgment instrument for predicting distributions and assigning credible subjective estimates. The predicted compounds provide crucial information about future pharmaceutical trends as well as benchmarks for use by the recycled water industry, public health regulatory agencies and consumer advocacy networks.