Vapor Intrusion and Chlorinated Solvents in Commercial and Industrial Settings

In 2015, the US EPA finalized and released its technical guidance for assessing and mitigating vapor intrusion from subsurface vapor sources into indoor air, as well as their vapor intrusion screening levels (VISLs). In January of 2017, the USEPA finalized the addition of vapor intrusion to the Hazard Ranking System (HRS) to evaluate sites on the National Priorities List (NPL). For chlorinated solvents, especially trichloroethylene (TCE), the VISLs for commercial and industrial settings are thousands of times lower than the occupational exposure limits established by OSHA and the ACGIH due to a study in rats showing birth defects in offspring when mothers were exposed to TCE in drinking water.  Understanding the proper use of OELs and VISLs in commercial and industrial settings, as well as the scientific basis for the lower VISL values, is important for effective assessment of worker risk and remediation of a vapor intrusion site. We will examine the toxicology and historical and current uses of TCE in addition to the current regulations. Case studies will be examined where TCE was elevated above the VISL’s but below occupational guidelines, in an effort to understand regulatory jurisdictions and the risk associated with TCE exposure, as well as the science behind various regulatory guidelines.  These understandings are key in ensuring appropriate remediation, worker safety, communication, disposal, and administrative controls when assessing and remediating a vapor intrusion site.