[CPEO-MEF] EPA proposes more protective toxicity value for TCE

[Lenny Siegel <lennysiegel@gmail.com>]

[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

--


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
<lsiegel@cpeo.org>
http://www.cpeo.org



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