Vapor Intrusion

What is Vapor Intrusion (VI)?

Vapor intrusion (VI) is the migration of vapor-forming chemicals from a subsurface source such as the soil and/or groundwater into the indoor air of an overlying building -- similar to the seepage of radon gas into homes. It migrates up through the air space in permeable soils, open fractures in bedrock or clay tills, utilities, sumps, or cracks in the building foundation. Vapors can travel along preferential pathways such as along porous soil surrounding utility pipes and cracks in the foundation and gaps of buildings where pipes enter the basement.

Trichloroethylene (TCE) in Air

Air contaminated with TCE is of serious concern due to the health dangers it poses when it's inhaled. Since it volatilizes very easily into the air, vapors contaminated with TCE can migrate from the TCE-impacted soil or groundwater underneath homes and buildings and migrate into the indoor air

TCE is a health concern because it is characterized as “carcinogenic to humans” by all routes of exposure (USEPA 2005b Guidelines for Carcinogen Risk Assessment).  In addition, it poses a noncancer toxicity (findings based on the 2011 IRIS Study) to the central nervous system, kidney, liver, immune system, male reproductive system, and the developing embryo/fetus (recent findings have indicated that fetal heart defects may result if pregnant women are exposed to TCE in their earliest stages of gestation).  The most common sources of non-occupational exposure to TCE are ambient air and drinking water.

Industrial uses of TCE are varied and include being used as a degreasing solvent for metal parts during the manufacturing process, as an extractor of caffeine from the coffee bean, and as an inhalant analgesic in childbirth (historically). It is a breakdown compound of tetrachloroethene (PCE), a common dry cleaning solvent that is also sometimes found in the soil and groundwater.

Supplemental Guidance: Screening and Evaluating Vapor Intrusion

The Department of Toxic Substances Control (DTSC), the State Water Board, and the San Francisco Bay Regional Water Quality Control Board (SF Bay Regional Water Board) are currently developing a supplemental vapor intrusion guidance document for conducting uniform vapor intrusion evaluations in California.  This guidance document, when finalized, will serve as a 2018 Supplement to existing guidance (namely, DTSC 2011 Vapor Intrusion Guidance and SF Bay Regional Water Board 2014 Interim Framework). It provides detailed information on the following topics:

• Soil gas, subslab, indoor air, and outdoor air sampling recommendations that are focused on understanding spatial and temporal variability
• Recommendations for use of USEPA 2015 attenuation factors
• Risk management framework for vapor intrusion
• California-specific vapor intrusion database

The Supplemental VI Guidance Document is under development and should be available to the public in the Winter of 2018 as an Interim final document.  Presentations on the topic have been conducted at two recent, industry conferences (2018 AEHS Conference Presentation and 2018 CUPA Conference Presentation).  DTSC and the Water Boards are planning public training likely in Northern and Southern California.  When the actual dates are established, they will be posted below.

Tools

Trichloroethelyne (TCE) Fact Sheet (Coming Soon)

Access Agreement Template (Coming Soon)

Geotracker Guidance on Uploading Vapor Intrusion Information into Geotracker

Databases

VI Contacts

Water Boards

DTSC

Resources

USEPA -

• USEPA Vapor Intrusion Website
• USEPA Health Hazard Assessments Noncarcinogenic/Carcinogenic Effects of TCE, dated 09/28/2011
• USEPA, Office of Solid Waste and Emergency Response,  Compilation of Information Relating to Early/Interim Actions at Superfund Sites and The TCE IRIS Assessment, dated 08/27/14
• USEPA, Office of Solid Waste and Emergency Response, 2015. OSWER Technical Guide for Assessing and Mitigating the Vapor Intrusion Pathway from Subsurface Vapor Sources to Indoor Air. OSWER Publication 9200.2-154

DTSC -

• DTSC Vapor Intrusion Website

Research Articles

• Environmental Health Perspectives Volume 121 Number 3 March 2013: Human Health Effects of Trichloroethylene: Key Findings and Scientific Issues, Weihsueh A. Chiu, Jennifer Jinot, Cheryl Siegel Scott, Susan L. Makris, Glinda S. Cooper, Rebecca C. Dzubow, Ambuja S. Bale, Marina V. Evans, Kathryn Z. Guyton, Nagalakshmi Keshava, John C. Lipscomb, Stanley Barone Jr., John F. Fox, Maureen R. Gwinn, John Schaum, and Jane C. Caldwell, March 2013
• Environmental Health Perspectives Volume 111 Number 3 March 2003: Threshold of TCE Contamination in Maternal Drinking Waters Affecting Fetal Heart Development in the Rat, Paula D. Johnson, Stanley J. Goldberg, Mary Z. Mays, and Brenda V. Dawson, March 2003

Waterboards Cleanup Programs

Brownfields Program

DoD Program

Site Cleanup Program

UST Program