EPA Eases Path to Superfund Listing: Vapor Intrusion Component Added to the Hazardous Ranking System

The U.S. Environmental Protection Agency (EPA) has just released a pre-publication version of its final rule to add a subsurface intrusion (SsI) component to the Superfund Hazard Ranking System (HRS).  EPA defines subsurface intrusion as the migration of hazardous substances, pollutants, and contaminants from the unsaturated zone or the surficial (shallow) ground water into overlying structures. The most common form of subsurface intrusion is vapor intrusion.  Vapor intrusion occurs when vapor-forming chemicals from sources including dry cleaning solvents and industrial de-greasers in ground water or soil migrate into buildings and other enclosed spaces, posing a threat to indoor air quality.

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