By:  Denise Kmetzo, DABT, Collaborative Risk Solutions, and Technical Practices Committee

Tetrachloroethylene, or PCE, is recognized as a toxic chemical and is considered likely to be carcinogenic in humans by all routes of exposure. The degree of its toxicity has been debated for years, especially for the inhalation route of exposure. Two years ago, the EPA finalized PCE toxicity factors, including an inhalation Unit Risk (UR) factor, which is used to assess carcinogenic risk via inhalation. The LSPA encouraged MassDEP to adopt the EPA toxicity values, including the UR. Instead, during its recent reevaluation of PCE toxicity, MassDEP’s Office of Research and Standards (ORS) relied upon a UR for PCE that it had previously derived.  In January 2014, MassDEP released an updated PCE UR which is lower (i.e., less conservative) than MassDEP’s previously derived value, but remains greater than ten times higher (i.e., more conservative) than the EPA value.