PROJECT SUMMARY/ABSTRACT Vapor Intrusion (VI) is a recently recognized, priority environmental health concern in the US. The VI problem involves volatile organic compounds (VOCs), which vaporize from contaminated soil or groundwater beneath homes and other structures, entering these buildings directly from the soil. VI represents a chronic, low-level exposure pathway in homes and schools, and there is increasing concern about associated health risks. A major problem in managing VI risk is the highly variable indoor contaminant concentrations that empirical field investigative methods can easily miss. This project focuses on developing a full three- dimensional model of VI that can reliably predict dynamic variability in indoor concentration levels. The modeling work will be informed by, and tested against, actual field measurements at two chlorinated solvent (TCE and PCE) VI sites in Rhode Island. Working with the RI Department of Environmental Management, and with the Research Translation and Community Engagement Cores, we will perform indoor measurements to establish the variability of indoor contaminant concentrations at well-characterized sites. The indoor measurements will include determining concentrations of VOCs, as well as factors that are important to the modeling work, such as air exchange rates, relevant indoor volumes, indoor depressurizations, and the inventory of sorption materials and surfaces. The dynamics of VOC partitioning to indoor surfaces requires further study to establish the role that such processes play in determining the variability in indoor concentrations. Thus, Project 3 also involves laboratory measurements of dynamic partitioning of VOCs of VI concern to common indoor materials. A biomedical-engineering collaboration between this project and Project 1 on Vapor Intrusion Modeling and Health Monitoring develops sensitive biomarkers that integrate the time- and exposure-related health effects of TCE on mammalian reproductive systems. A collaboration with Project 4 focuses on development of graphene-based vapor barriers to limit entry of vapors into structures. The project hypothesis is that the variability in VI indoor air contaminant concentrations can be captured in 3-dimensional computational modeling. The goals will be achieved through three Specific Aims: Specific Aim 1: To develop a 3-D computational tool to predict time-varying indoor VOC concentrations Specific Aim 2: To conduct field sampling at Rhode Island VI sites for model development and validation Specific Aim 3: To measure dynamic VOC partitioning on diverse materials in indoor environments as an input to the dynamic modeling. Project 3 will work in close collaboration with the Rhode Island Dept. of Environmental Management, and will rely upon strong interactions with the Research Translation and Community Engagement Cores.