2009 CPEO Military List Archive

From: Lenny Siegel <lennysiegel@gmail.com>
Date: Thu, 5 Nov 2009 14:09:39 -0800 (PST)
Reply: cpeo-military
Subject: [CPEO-MEF] EPA proposes more protective toxicity value for TCE
[Please excuse the duplicate posting. - LS]

On Tuesday, November 3, U.S. EPA published a Federal Register notice releasing the External Review Draft of its Toxicological Review of Trichloroethylene for public review and comment. Comments are due by February 10, 2009. See http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=215006

Trichloroethylene (TCE) is not only one of the most common groundwater contaminants in the U.S., but with its sister chemical, tetrachloroethylene (PCE), it is responsible for most of the vapor intrusion sites requiring a response. This new finding, if finalized, should lead to a more aggressive mitigation of indoor air in buildings overlying TCE groundwater plumes.

I have have not reviewed the document in detail yet, but if adopted, the exposure level associated with a one-in-a-million excess lifetime cancer risk, in a residential (round-the-clock) scenario will be .25 micrograms per cubic meter. (I need to check this, but I've been told that a childhood age adjustment for kidney cancer may drive the number down to .20 ug/m3.) If finalized, this will become the indoor air action level for vapor intrusion response in many jurisdictions. In most metropolitan areas, this is close to background - that is, ambient outdoor air concentrations.

Where regulatory agencies use the one-in-a-million level, this means that mitigation would be required anywhere TCE levels in homes and schools are above background. It is not possible, in most circumstances, to drive indoor air levels below what is in the outdoor air.



Lenny Siegel
Executive Director, Center for Public Environmental Oversight
a project of the Pacific Studies Center
278-A Hope St., Mountain View, CA 94041
Voice: 650/961-8918 or 650/969-1545
Fax: 650/961-8918

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