Development of Standardized Guidance and Tools to Strengthen Environmental Exposure Assessment

Risk assessors and other scientists use environmental sampling data to understand and quantify how people are exposed to contamination. But the sampling data are often limited, uneven, and difficult to interpret. The most robust approach for quantifying exposures depends on sampling design, numbers of samples collected, the distribution of measured concentrations, and other factors. Further, some classes of contaminants present unique challenges in collapsing sampling data for multiple individual chemicals onto an indicator of aggregate exposure. The Agency for Toxic Substances and Disease Registry (ATSDR) recognized these challenges and identified the need for clear and consistent exposure assessment methodologies. The agency sought ERG’s support to establish standardized, statistically robust guidance for interpreting environmental data and quantifying exposures to environmental contamination.

ERG supported ATSDR in developing multiple guidance documents addressing data evaluation for both discrete and non-discrete sampling, as well as substance-specific guidance for polycyclic aromatic hydrocarbons (PAHs) and dioxins. This guidance standardizes calculations for exposure point concentrations (EPCs) and toxic equivalency metrics across sampling designs and contaminant classes, ensuring consistency and technical defensibility in public health assessments.

ERG also translated complex statistical and toxicological methods into clear, step-by-step procedures that risk assessors can readily apply to sampling data for multiple environmental media. To further enhance usability and efficiency, ERG developed the ATSDR EPC Tool, a web-based application that automates key steps from the underlying guidance documents. The EPC Tool enables users to rapidly calculate EPCs and toxicity-weighted values through a verified workflow that integrates with ATSDR’s broader assessment tools, supporting reliable and health-protective evaluation of environmental data.