|From:||Lenny Siegel <email@example.com>|
|Date:||28 Oct 2004 06:57:54 -0000|
|Subject:||[CPEO-BIF] New York's standard for TCE in air|
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
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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