Illustrative case using the RISK21 roadmap and matrix: prioritization for evaluation of chemicals found in drinking water

ABSTRACT

The HESI-led RISK21 effort has developed a framework supporting the use of twenty-first century technology in obtaining and using information for chemical risk assessment. This framework represents a problem formulation-based, exposure-driven, tiered data acquisition approach that leads to an informed decision on human health safety to be made when sufficient evidence is available. It provides a transparent and consistent approach to evaluate information in order to maximize the ability of assessments to inform decisions and to optimize the use of resources. To demonstrate the application of the framework’s roadmap and matrix, this case study evaluates a large number of chemicals that could be present in drinking water. The focus is to prioritize which of these should be considered for human health risk as individual contaminants. The example evaluates 20 potential drinking water contaminants, using the tiered RISK21 approach in combination with graphical representation of information at each step, using the RISK21 matrix. Utilizing the framework, 11 of the 20 chemicals were assigned low priority based on available exposure data alone, which demonstrated that exposure was extremely low. The remaining nine chemicals were further evaluated, using refined estimates of toxicity based on readily available data, with three deemed high priority for further evaluation. In the present case study, it was determined that the greatest value of additional information would be from improved exposure models and not from additional hazard characterization.

Keywords:

• Drinking water
• integrated evaluation strategy
• prioritization
• risk assessment
• RISK21
• tiered approach

Acknowledgements

The authors gratefully acknowledge the government, academic and industry scientists of the HESI RISK21 Technical Committee for their contributions to this work. A full list can be accessed at www.risk21.org. The comments of four reviewers selected by the Editor and anonymous to the authors were helpful in revising the article.

Declaration of interest

The authors’ affiliations are as shown on the cover page. The authors had sole responsibility for the writing and content of the article. The views and opinions expressed in the article are those of the authors, and do not necessarily reflect the views of the authors’ employers or the opinions or policies of the US EPA. Mention of trade names does not constitute endorsement. None of the authors has recently or is currently involved as an expert witness in litigation or formal government rule-making on the subject of this article. None of the authors received financial support or an honorarium in the preparation of this article. The authors declare that there are no conflicts of interest.