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Vapor Intrusion Newsletter

		Vapor Intrusion News

In This Issue:

December 2002

*	EPA Issues Vapor Intrusion Guidance

*	Status of TCE Action Level

*	EPA Guidance Training Seminars

*	New Research on Background VOC Concentrations

*	Status of 1,1-DCE Action Level

EPA Issues Vapor Intrusion Guidance

On November 29, 2002 EPA published a notice in the Federal Register seeking comment on draft guidance for "Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils" by February 27, 2003. The guidance provides a tiered procedure for determining whether vapor intrusion poses an unacceptable risk to human health. The guidance is recommended for use at RCRA corrective action sites, federal Superfund and Superfund Alternative sites, and Brownfield sites. At this time, the guidance is not recommended for use at Subtitle I Underground Storage Tank sites and does not supercede State guidance where it exists. The document is available for use as a draft and it is not expected to be finalized for a significant period of time.

The guidance is structured around six questions which consecutively become more site specific. Generic screening levels are provided for groundwater concentrations to screen out sites where the potential for vapor intrusion is low; however, the screening levels for several compounds are set at their MCL values. Sites that are not screened out by the table values may require more site specific evaluation, including sub-slab soil vapor or indoor air tests. The guidance does not address delineation of extent of vapor intrusion impacts or mitigation techniques. Visit www.envirogroup.com for more information, including papers and links, on these topics.

Download guidance and Federal Register notice

EPA Guidance Training Seminars

EPA's Office of Research and Development (ORD) is sponsoring 3 two-day seminars on vapor intrusion, introducing the new EPA guidance and enabling dissemination and exchange of state-of-the-art information. Topics include the new guidance, risk characterization, sampling methods, models, and state and industry perspectives. The first seminar was held in San Francisco on December 3-4, 2002. The next two seminars will be held in Dallas on January 14-15 and Atlanta on February 25-26. Dave Folkes of EnviroGroup (dfolkes@envirogroup.com) will be speaking on mitigation of vapor intrusion, based on experience mitigating several hundred buildings.

Status of 1,1-DCE Action Level

Until recently, 1,1-dichloroethylene (1,1-DCE) was the primary risk driver at many vapor intrusion sites. However, changes to the toxicity criteria for 1,1-DCE have resulted in much higher EPA indoor air action levels for this compound. 1,1-DCE is used in flexible film plastics, such as food wrap, flame retardant coatings, and adhesives, and is a common breakdown product of 1,1,1-TCA and TCE in groundwater. On August 13, 2002 EPA finalized its reassessment of 1,1-DCE and placed new toxicity criteria for this compound into the Integrated Risk Information System (IRIS) data base. EPA found that available information was not sufficient to develop a quantitative estimate of carcinogenicity and removed the previous cancer slope factor. The reassessment did, however, produce a reference concentration for 1,1-DCE for chronic inhalation exposure based on non-cancer effects. The net result of these changes is an indoor air concentration protective of human health that is more than 400 times higher than the previously used number (based on a 10-5 cancer risk level) . The tables in the recently released draft EPA vapor intrusion guidance (see first article) use this new information and include an indoor air screening level of 200 ug/m3 for 1,1-DCE. It should be noted, however, that some states such as Colorado are still using the old cancer slope factor and, as a result, very low indoor air action levels for this compound (e.g., 0.49 ug/m3 at a 10-5 risk level).

Link to new 1,1-DCE Toxicity Criteria

Status of TCE Action Level

Impending changes to the toxicity criteria for TCE, a common degreasing solvent, may cause TCE to be the new risk driver at many vapor intrusion sites. EPA's Integrated Risk Information System (IRIS) presently contains no quantitative toxicity information for TCE. The carcinogenicity assessment, which had been included in IRIS, was withdrawn in 1994. EPA risk assessments, nevertheless, have treated TCE as a carcinogen over the years and used the withdrawn cancer slope factor in their calculations while EPA has been conducting a reassessment of the toxicity of TCE. The old cancer slope factor results in moderately low indoor air action levels (e.g., 14 ug/m3 at a 10-5 risk level). In August 2001 EPA released its Trichloroethylene Health Risk Assessment for external review. That assessment found that TCE caused several cancer and non-cancer health effects and presented a range of cancer slope factors. On June 18-19, 2002 EPA's Science Advisory Board conducted a peer review of this document. EPA is currently reviewing the results of that peer review and deliberating its final course of action for TCE. The tables in the recently released draft EPA vapor intrusion guidance use the information presented in the 2001 Trichloroethylene Health Risk Assessment even though that information has not yet been loaded into IRIS. They are called "provisional" values in the guidance. Table 2b of the guidance presents a generic indoor air screening level of 0.22 ug/m3 for TCE (based on a cancer risk level of 10-5 ). This is a very low level which is close to the detection level of most laboratories and may be within the background range for residential indoor air (see next article). Based on this information TCE will likely now become the risk driver at many indoor air sites. EPA and some states are using this new toxicity information for risk evaluations and action levels and others are still reviewing the situation.

Link to current TCE Toxicity Criteria

New Research on Background VOC Concentrations

The indoor air screening levels for many VOCs are well within the range of residential background concentrations due to household products and building materials (see Kurtz and Folkes 2002 and others). The potential for background contributions to indoor air VOCs should be considered during all screening evaluations and development of action levels. Very little high quality information is available on indoor air background levels for VOCs, in part because the analytical procedures capable of measuring these low concentration levels were not generally available until recently. New research by Kurtz and Folkes (2002) and others have provided some of the best measurements of background concentrations, including compounds for which no background data were previously available.

Kurtz and Folkes (2002). From Indoor Air 2002.

This newsletter is issued periodically to provide readers with information on new regulatory and technical developments in the rapidly changing field of vapor intrusion. While every effort is made to ensure that the information and links presented in this newsletter are accurate at the time of publication, they are presented for general informational purposes only. Users should independently verify the accuracy and applicability of this information for any specific sites or purposes. Copyright EnviroGroup Limited 2002. More information about EnviroGroup Limited