Detection of 1,4-dioxane has been reported in shallow groundwater in neighborhoods of the city of Ann Arbor, Michigan. Michigan has a voluntary 1,4-dioxane shallow groundwater screening level based on its potential for vapor intrusion. Calculations show that if 1,4-dioxane-contaminated water were to enter a basement and evaporate, potentially unhealthy concentrations of 1,4-dioxane could arise in homes with damp basements under certain conditions. Potential residential risk is suggested if: 1) shallow groundwater is within 3 m of the surface, 2) groundwater 1,4-dioxane concentration exceeds 150 μg/L, and 3) a basement has higher humidity than the upper floors. Different from vapor intrusion, this suggests that liquid water intrusion with subsequent volatilization within a structure may be a novel exposure pathway for 1,4-dioxane.
Keywords: 1,4-Dioxane pollution; Indoor air pollution; Protective air concentration; Shallow groundwater; Vapor intrusion; Volatilization.