Vapor Intrusion

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What is vapor intrusion?
What is the purpose of a vapor intrusion investigation?
What happens if vapor intrusion is suspected?
What can be done to reduce vapor intrusion and improve indoor air quality?
Information about sampling results and decisions made at vapor intrusion sites
Vapor Intrusion and Drinking Water
For more information

What is vapor intrusion?

Chemicals that have been spilled or dumped on the ground can pollute soil and groundwater. Volatile organic compounds (VOCs) are chemicals that easily evaporate into air. The most commonly found VOCs during vapor intrusion investigations in Minnesota are the industrial degreaser trichloroethylene (TCE), the dry cleaning solvent tetrachloroethylene  (perchloroethylene, PCE), and components of petroleum. VOCs that evaporate from polluted soil and groundwater rise towards the ground surface. If these vapors come to a building as they travel to the surface, they may enter through cracks in the foundation, around pipes, or through a sump or drain system. The VOCs can then contaminate indoor air. This process - when pollution moves from air spaces in soil to indoor air - is called vapor intrusion.

Radon also enters buildings from soil through vapor intrusion. Radon is an odorless, radioactive gas that occurs naturally in soils. Radon is the number one cause of lung cancer in non-smokers. In Minnesota, about 40% of homes have radon levels that pose a significant health risk. For more information about radon and radon testing, visit Radon in Minnesota Homes. There are options available for homeowners to lower exposure to radon in their homes.

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What is the purpose of a vapor intrusion investigation?

The purpose of vapor intrusion investigations is to determine if there is a possible risk to the health of people that can be stopped. For there to be a health concern, contaminated vapor has to get into the indoor air at relatively high levels AND people need to breathe the contaminated indoor air vapor over time.

Homes included in a vapor intrusion investigation are chosen with the aim of finding out whether there is any risk for vapor intrusion or a potential health concern. Health risks from vapor intrusion are usually low. However, because they are avoidable, we want to take steps to reduce or eliminate vapor intrusion where possible.

Vapor intrusion investigations are common in Minnesota and across the nation. For more information about investigations in Minnesota, visit the Minnesota Pollution Control Agency (MPCA) Vapor Intrusion Web pages.

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What happens if vapor intrusion is suspected?

Officials investigate by collecting soil, groundwater, and soil vapor samples to look for the presence of chemicals and the amounts of chemicals. If chemicals are present near buildings, it may be necessary to collect samples of sub-slab soil vapor or indoor air. Sub-slab samples are collected by drilling a small hole through the slab to collect a sample of soil vapor from beneath the building. Sub-slab and indoor air samples are collected using special canisters.

Usually, when contamination is the result of a spill or leak, the responsible party or a government agency pays for the investigation and cleanup.

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What can be done to reduce vapor intrusion and improve indoor air quality?

If the MPCA finds soil vapors under your home that could indicate a concern, it will offer to install a mitigation system to remove vapors from beneath the foundation and vent the vapors to the outside air.   In nearly all cases this is done at no cost to the homeowner. These are the same systems commonly used to keep radon from entering homes. They are relatively inexpensive to operate, simple to design and install, and are a proven solution to radon and vapor intrusion problems.

For more information about mitigation systems, see Radon Mitigation Systems.

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Information about your sampling results and decisions made at vapor intrusion sites.

MPCA and MDH work together to evaluate vapor intrusion risks at sites under investigation. Decisions about actions taken at a vapor intrusion investigation site are based on the combination of known information and/or guidance about chemical safety and sampling data taken from buildings in the investigation area.

Information about chemicals commonly found at vapor intrusion sites in Minnesota.

For more information about TCE:

For more information about PCE:

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Vapor Intrusion and Drinking Water

Vapor intrusion is often associated with shallow groundwater or soil contamination. Municipal drinking water usually comes from deep wells or surface water. Therefore, drinking water is generally not impacted by the type of contamination found at vapor intrusion sites.

If you receive your drinking water from a public water supply, it is monitored through the federal Safe Drinking Water Act. Annual water quality reports (Consumer Confidence Reports or CCRs) are available through your local water utility and may be posted on its website.

If you use a private well for drinking water and your home is undergoing a vapor intrusion investigation, contact us for more information.

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For more information

For health-related questions regarding vapor intrusion or contaminated sites, please contact us

Printable information sheet: Vapor Intrusion (PDF)

Prepared in cooperation with the
US Agency for Toxic Substances and Disease Registry

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Updated Friday, January 29, 2016 at 02:21PM