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November 13, 2009
It's a Gas
A search of EnviroReporter.com for the toxic solvent trichloroethylene (TCE) will yield no less than 31 pages and posts. There’s a reason for that: TCE is one of the most pervasive toxins plaguing California and over a dozen other states.

But a breath of fresh air may be in store. On November 3, the U.S. Environmental Protection Agency released the External Review Draft of its Toxicological Review of Trichloroethylene for public review and comment.

The agency has taken the extraordinary step of recommending that levels of TCE permeating indoor air should be cut by over four times its current goal. The action, which has vast implications especially in Southern California, is in response to the challenge this contaminant poses to public and environment, according to the agency’s website:

The draft Toxicological Review of Trichloroethylene (TCE) provides scientific support and rationale for the hazard and dose-response assessment pertaining to chronic exposure to TCE. TCE is a chlorinated solvent that has been widely used as a metal degreaser, as a chemical intermediate and extractant, and as a component of some consumer products. TCE is designated as a Hazardous Air Pollutant, is a common groundwater contaminant, and has been found at more than 1,500 hazardous waste sites. TCE enters the atmosphere from vapor degreasing operations or volatilization from contaminated soils, surface waters via direct discharges, and groundwater through leaching from disposal operations and hazardous waste sites. In addition, TCE can be released to indoor air from the use of TCE-containing consumer products, volatilization from water supplies, and vapor intrusion through walls and floors from contaminated soil and groundwater.

That means gunk in the groundwater can rise through the soil in gaseous form and collect in above-ground structures like homes, schools and churches. If you’re living over a TCE plume, like inhabitants in Scottsdale Arizona who don’t have specialized ventilation systems, it might be a good idea to keep the windows open.

Drinking small amounts of TCE for long periods may cause impaired immune system function, liver and kidney damage and impair fetal development in pregnant women. Larger drinking doses may cause liver damage, nausea, impaired heart function, unconsciousness or death. Breathing small amounts may cause dizziness, lung irritation, headaches, difficulty concentrating and poor coordination. Inhaling large amounts of TCE may cause unconsciousness, impaired heart function and death.

The TCE exposure level associated with a one-in-a-million excess lifetime cancer risk, in a round-the-clock residential scenario is being lowered to .25 micrograms per cubic meter, or ug/m3. It may be even lower adjusting for childhood kidney cancer, just .20 ug/m3. Currently, EPA Region 9, based in San Francisco, uses 1.0 ug/m3 based upon state EPA research but California uses the higher level of 1.2 ug/m3.

If the new rule is finalized, it will become the “indoor air action level” for vapor intrusion response in many areas for environmental agencies. The .25 ug/m3 level is close to the amount of TCE in the air of America’s metropolitan areas, called the ambient outdoor air concentration. Where the one-in-a-million public health goal is in effect, mitigation would be required anywhere TCE levels are above background in homes and schools.

“If adopted, the proposed new toxicity value for TCE should drive the re-opening of site environmental decisions wherever indoor air contamination levels have been found to be barely acceptable,” Lenny Siegel tells EnviroReporter.com.

Siegel is the director of the Mountain View, California-based Center for Public Environmental Oversight, or CPEO. The group encourages public participation in decisions related to Superfund and Brownfield sites across the nation and has been ringing the alarm bell about TCE for years.

“In fact, mitigation (substructure depressurization) should be built into any structure where indoor TCE levels exceed outdoor levels, or any site which has serious TCE contamination remaining in shallow groundwater,” says Siegel.

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