New Software Package for Modeling Vapor Intrusion

Vapor intrusion—or migration of vapors from contaminated soil or groundwater into buildings—can be an important indoor air quality issue at Superfund and other contamination sites. The Johnson & Ettinger model (JEM) is a widely used screening tool for evaluating this pathway. The Agency for Toxic Substances and Disease Registry (ATSDR) needed to apply the JEM to a complex vapor intrusion site with dozens of volatile contaminants affecting more than 50 buildings. However, the publicly available tools did not scale to this level of analysis and were limited to evaluating one contaminant and one building at a time. These tools also had limited ability to evaluate uncertainty and variability, thus complicating risk characterization efforts. To address these challenges, ATSDR asked ERG to develop an improved modeling approach that would streamline analyses and provide a more complete basis for evaluation and decision-making.

ERG worked with ATSDR to develop the vapintr R package—an open-source platform that makes advanced vapor intrusion modeling more accessible and easier to apply. The package streamlines analyses by enabling simulations for multiple contaminants within a single workflow and includes built-in data validation checks to ensure accurate results. ERG also incorporated Monte Carlo simulation capabilities to better enable assessment of uncertainty and variability in vapor intrusion. The package provides clear visualizations of both inputs and results, including distributions of predicted indoor air concentrations and comparisons with measured data and screening levels, making modeled outputs easier to interpret. An intuitive R Shiny interface allows users to run and review analyses, and the model accommodates both single-building and multiple-building assessments. These capabilities support more efficient and informed risk evaluation and decision-making, positioning vapintr as a valuable tool in vapor intrusion site assessments. The vapintr package source code is available for download at https://github.com/CDCgov/vapintr.