Be alert for vapor intrusion of 1,4-dioxane from contaminated groundwater.

Vapor intrusion (VI) poses significant environmental problems that can degrade indoor air and pose human health risks. This study focuses on 1,4-dioxane, a widely-used volatile organic compound (VOC) that is found in groundwater, however, this compound has not received much attention in indoor air and measurement methods are not well developed. 1,4-dioxane is sufficiently volatile and highly mobile in groundwater, and thus can present a VI risk. In this study, we develop a sensitive analytical method for quantifying airborne 1,4-dioxane, provide a performance evaluation of the method, and initiate preliminary field measurements above a 1,4-dioxane groundwater plume. The method uses passive sampling, automated thermal desorption, and gas chromatography/mass spectroscopy. Numerous other VOCs can be simultaneously measured. A low detection limit (0.067 μg/m3) is attained, which allows quantification at concentrations below health-based guidelines. The performance evaluation suggests limits to sampling times in high humidity environments and other means to ensure good performance. The scenario analyses demonstrate potential impacts from shallow plumes, especially in flooded basements, and thus monitoring of 1,4-dioxane vapor intrusion in the flood season is an urgent need.