As reported here and here, MassDEP’s Final Interim Vapor Intrusion Policy (pdf) is causing consternation among property owners who had thought that their state-managed cleanup sites had been given a clean bill of health, only to have those sites re-opened when MassDEP dramatically reduced the acceptable levels of certain chemicals found in groundwater below the sites.  A commonly-found chemical that has the potential to emit contaminated vapor, and thereby compromise the indoor air quality of buildings on those sites, is PCE (perchloroethylene) – also known as perc – a chemical long used by dry cleaners. 

MassDEP and EPA have had a long-standing disagreement on the harmful effects of PCE.  This disagreement was brought into sharper focus last month when EPA released its risk assessment of PCE (for those who get woozy reading scientific reports, this fact sheet is a more manageable read).  The upshot of all this is that EPA’s assessment of the risk from inhaling PCE is about 40 times less stringent than MassDEP’s assessment.  This means that if MassDEP used EPA’s PCE risk assessment numbers, many sites re-opened by MassDEP under its Vapor Intrusion Guidance would have remained closed, or could be closed again without further remediation.  

In light of this latest development, expect the regulated community to pressure MassDEP to adopt EPA’s findings.  But don’t look for a quick resolution of this issue.  Agencies move slowly and their science even slower – it took EPA 20 years to compile and release its PCE findings.