[CPEO-BIF] New York lowers PCE air guideline

[Lenny Siegel <lsiegel@cpeo.org>]

In September 2013 the New York State Department of Health (NYS DOH)  
finally lowered its inhalation guideline for tetracholoroethene (PCE  
or perc), but the level is not as low as some of us had hoped. See  
www.health.ny.gov/environmental/chemicals/tetrachloroethene/index.htm  
for the official fact sheet.

The new guideline is 30 micrograms per cubic meter (ug/m3) or 4.4  
parts per billion by volume (ppbv), replacing the 100 ug/m3 value  
established in 1997. The new value is not as low as the number (4 ug/ 
m3) that New York says EPA gives for a one-in-a-million excess cancer  
risk (based upon continuous lifetime exposure), and it is far from  
California's .41 ug/m3 threshold.

The "ambient air" guideline is not a bright line. "NYSDOH recommends  
that reasonable and practical actions should be taken to reduce PERC  
exposure whenever air levels are above background." Furthermore,  
NYSDOH's action matrix for PCE vapor intrusion takes into account  
soil gas levels as well as indoor air levels. Still, the new  
guideline appears to be based on residential (continuous) exposures,  
so the guideline for workplaces or schools impacted by subsurface PCE  
sources could be five times higher.

The PCE air guideline is particularly important for New York City,  
where only one groundwater area supplies drinking water. The city is  
dotted with "rogue" PCE plumes from current and former dry-cleaning  
establishments. The plumes present a risk of vapor intrusion, but  
with the guideline remaining so high it's not clear how many of them  
will be addressed with mitigation (such as substructure  
depressurization) or cleanup.

--

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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