[CPEO-BIF] New York's standard for TCE in air

[Lenny Siegel <lsiegel@cpeo.org>]

Community activists in New York state have been wondering for some time 
exactly what is the basis for the 5 micrograms per cubic meter health 
guideline underlying the state's investigation of vapor intrusion at 
sites contaminated with trichloroethylene. Some of the answers appear to 
lie in a year-old letter (October 31, 2003) from Nancy Kim, Director of 
the Division of Environmental Health Assessment at the New York State 
Department of Health to Dale Desnoyers, Director of the Division of 
Environmental Remediation at the New York State Department of 
Environmental Conservation.

The health assessors evaluated air exposure levels associated with a one 
in a million excess lifetime cancer risks to a 70-kilogram person, and 
came up with a range of .06 to 1 micrograms per cubic meter based on 
human health studies, but they concluded that the studies upon which the 
estimate was based were inadequate: "Confidence in these estimates is 
low because of the small number of cases, the inability to adequately 
control the potential influence of confounders,  unavoidable 
uncertainties in the exposure estimates, and the lack of a clear 
dose-response relationship."

Based on animal studies, they estimated an exposure range of .2 to 4 
micrograms per cubic meter for one-in-a-million excess lifetime cancers. 
Kim wrote, "Because there is a lack of scientific consensus on the 
appropriate animal surrogate and cancer sites, dose metric, and the 
method for scaling dose across species, no single estimate is preferred."

The health assessors evaluated three types of non-cancer effects - 
central nervous system, liver, and developmental - based upon both 
animal and human studies. This produced a "potential criteria range from 
about 1 microgram per cubic meter to 10 micrograms per cubic meter.

Kim explained how those number led to the 5 micrograms per cubic meter 
exposure guideline:

"After reviewing the data of the non-cancer and cancer effects of TCE 
and the potential criteria for long-term exposure of the general 
populations based on these effects, the New York State Department of 
Health has set an air guideline for TCE of 5 micrograms per cubic meter. 
The margins-of-exposure between this guideline and the TCE air levels 
known to cause non-cancer effects in animals are consistent with 
recommended procedures and are adequate when considered in conjunction 
with the limitations of the different studies. Similarly, the estimated 
increased human cancer risks associated with lifetime continuous 
exposure to 5 micrograms per cubic meter are in the risk range [one in 
one million to one in ten thousand] that is generally used by regulatory 
agencies when making decisions.

Lenny
--
Lenny Siegel
Director, Center for Public Environmental Oversight
c/o PSC, 278-A Hope St., Mountain View, CA 94041
Voice: 650/961-8918 or 650/969-1545
Fax: 650/961-8918
http://www.cpeo.org


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