A Resolution of Sorts on TCE

TCE is a prime example among many of the difficulties we face trying to assess and manage the risks from low levels of chemicals in the environment. EPA has been undergoing a torturous risk assessment process since 2001 in order to set regulatory limits. The original TCE risk assessment received abundant criticisms from stakeholders, principally DOD and industries undergoing cleanup of TCE-contaminated sites. Some of those comments could be considered exercises in “manufactured uncertainty”; however, others were on the mark in identifying flaws in EPA’s analysis. Eventually the TCE risk assessment ended up with the National Academy of Sciences, which in 2006 issued a report that partially vindicated EPA, and partially confirmed what EPA’s critics were saying, but in the end, recommended that EPA revise its risk assessment, and quickly. Last year, Congress started getting into the act, sponsoring legislation to set a timeline for EPA to complete its scientific review and propose numbers that could be used for setting cleanup and drinking water standards. This only heightens the unreality of the situation; one would think with war, global climate change, economic meltdown and a crisis in healthcare, Congress would have better things to do with its time than debate the cleanup standards of ONE Superfund contaminant, no matter how prominent it is.

Earlier this month, there was a bit of a resolution on this issue, as reported in the March 18, 2008 Risk Policy Report, published by Inside EPA. At the meeting of federal facilities managers sponsored by the Association of State and Territorial Solid Waste Management Officials (ASTSWMO), EPA announced they it had reached an agreement in principle with the Department of Defense (DOD) on cleanup levels to address inhalation exposures to TCE associated with vapor intrusion. According to the Risk Policy Report:

The move will provide DOD and industry a long-sought consistent national approach to the issue, a DOD source says, as well as allow regulators across the country to make long-delayed cleanup decisions to address vapor intrusion, a previously unrelated pathway that results from toxic vapors from underground solvents that enter homes, offices and other structures

EPA has developed provisional guidance that will adopt the risk assessment prepared by the California Environmental Protection Agency for purposes of setting cleanup standards for vapor intrusion pathways. This will provide some badly-needed consistency in cleanup policy, which will allow remedial actions to move forward (I’ve personally observed sites where action has been stalled over differences in opinion about appropriate risk-based standards for TCE). Currently, state and federal agencies are using a variety of risk assessments which provide up to a 65-fold range in cleanup levels, for the same target cancer risk. EPA states that cleanups should achieve indoor air concentrations ranging from 1 to 10 ug/m3; the ability to protect public health with these levels in air is a matter for further discussion (I’m working on a longer post discussing that issue), but it’s possible that 1 to 10 ug/m3 in air represents levels that can be reasonably achieved with Superfund remedial technologies.

I’ll be back with more on this topic.