Workshop ReportThe importance of problem formulations in risk assessment: A case study involving dioxin-contaminated soil

•Contaminated soil cleanup screening level default assumptions have some uncertainty.•Pathways other than soil may have more significant exposures.•Recent NAS report recommends a problem formulation step prior to risk assessment.•Significant exposure pathways approach allows for relevant risk management.•Several approaches for soil dioxin concentrations are addressed in this manuscript.

The need to remediate contaminated soils is typically accomplished by applying standard risk assessment methods followed by risk management to select remedial options. These human health risk assessments (HHRAs) have been largely conducted in a formulaic manner that relies heavily on standard deterministic exposure, toxicity assumptions and fixed mathematical formulas. The HHRA approach, with its traditional formulaic practice, does not take advantage of problem formulation in the same manner as is done in ecological risk assessment, and historically, has generally failed to emphasize incorporation of site-specific information. In response to these challenges, the National Academy of Sciences recently made several recommendations regarding the conduct of HHRAs, one of which was to begin all such assessments with problem formulation. These recommendations have since been extended to dose response assessment. In accordance with these recommendations, a group of experts presented and discussed findings that highlighted the importance and impact of including problem formulation when determining the need for remediation of dioxin contamination in soils, focusing in particular on exposure assessment is described.