MCP Regulatory Reform Project Complete

The Regulatory Reform revisions to the Massachusetts Contingency Plan are effective June 20, 2014 (with some provisions in effect as of April 25, 2014).

This concludes BWSC “Reg Reform” project, although the program is committed to continually evaluating and improving the regulations, policy and guidance as appropriate.  Please check the MassDEP Waste Site Cleanup web page for any new projects or initiatives.



June 7, 2013 Numerical Standards Meeting

MassDEP held a meeting for parties wishing to expand upon the information and reasoning underlying the comments submitted on the proposed changes to the MCP numerical standards on June 7, 2013.

We appreciate the thoughtful comments on the proposed MCP standards and the risk assessment-related revisions that many of you have contributed.  We will be making revisions and preparing responses to comments throughout the summer.

Material from the meeting:

Support Material for Revised MCP Method 1 Standards

As part of the MCP Reg Reform package, MassDEP has proposed revisions to the MCP Method 1 Standards. The following files contain support documentation and references that reviewers may find useful while preparing comments on the proposal.  Questions about this material may be addressed to Nancy Bettinger in the MassDEP Office of Research and Standards at

Method 1 Standards Documentation and References

Chemical-Specific Toxicity Information

Information for the GW-3 Standards

Indoor Air Background

Relative Absorption Factors (RAFs)

Toxicity Value References

PCE Toxicity Value Review

On February 10, 2012, U.S. EPA published a final Health Assessment for Tetrachloroethylene (Perchloroethylene, or “Perc” or PCE) on the IRIS database ( In the new Health Assessment, EPA provides revised toxicity values for oral exposures (a reference dose [RfD] for non-cancer and a cancer slope factor [CSF] for cancer risk) and for inhalation exposures (a reference concentration [RfC]for non-cancer and an inhalation unit risk factor [URF] for cancer).

Several years ago, while EPA’s Health Assessment was still in progress, assessment of tetracholorethylene in indoor air arose as a critical issue for a number of MCP sites.  The Bureau of Waste Site Cleanup (BWSC) requested that the Office of Research and Standards (ORS) review the inhalation unit risk factor (URF, for evaluating cancer risk from exposure to air contaminants) in use at the time.  ORS toxicologists conducted the review of the scientific literature available at the time, obtained a peer-review of the ORS assessment, and published a revised inhalation unit risk value in 2008 (

In addition to the URF published in 2008, ORS has recently reviewed and updated the RfC used to calculate MassDEP’s Threshold Effects Limits (non-cancer) for tetrachloroethylene (  This review considered all of the toxicological data currently available.

Some of the toxicity values published in EPA’s Health Assessment differ significantly from those developed by MassDEP.  ORS plans to review the basis for the values provided by EPA before adopting final values.  MassDEP expects to complete the review by the end of March. Until then, MassDEP recommends the continued use of the MassDEP cancer slope factor of 5 x 10-2 (mg/kg/day)-1 and the inhalation unit risk of 1 x 10-5 (µg/m3)-1 for site-specific risk assessments conducted under the Massachusetts Contingency Plan (310 CMR 40.0000).

Any questions may be directed to

Updated Toxicity Value Tables

MassDEP has updated the list of revised toxicity values provided for and discussed at the February 3, 2012 Standards meeting.

The new documents can be downloaded here:

– Nancy Bettinger, MassDEP Office of Research & Standards (

Feb. 3 Meeting Material

Material for the February 3, 2012 meeting is now available from the Standards discussion page: