Vapor Intrusion - Environmental Health: Minnesota Dept. of Health

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?
Vapor Intrusion and Drinking Water
Information about sampling results and decisions made at vapor intrusion sites
For more information

Dissolved contamination in groundwater leads to contaminated vapor as it moves through soil. The contaminated vapor travels through the floor or wall cracks and into the building's basement and may contaminate the air.

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.

VOCs that evaporate from polluted soil and groundwater rise toward 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.

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.

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What is the purpose of a vapor intrusion investigation?

The purpose of a vapor intrusion investigation 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.

Buildings 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, the risks may be greater when people are exposed to high amounts of some chemicals for a long time, or if exposed people are sensitive or their health is compromised.

Examples of people who may be sensitive include:

  • women who are pregnant or may become pregnant
  • infants and young children
  • elderly persons
  • people who are living with chronic disease or a compromised immune system

Because the risks are avoidable, we want to take steps to reduce or eliminate vapor intrusion where possible. If you have concerns about anyone living in your home or building who may be a sensitive individual, please contact MDH.

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What happens if vapor intrusion is suspected?

Vapor intrusion is investigated by collecting environmental 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 from beneath the building. Sub-slab samples are collected by drilling a small hole through the building foundation. Indoor air samples may also be collected. Samples are collected in special canisters.

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

If soil vapors are found under your home or building that could indicate a concern, a mitigation system can be installed to remove vapors from beneath the foundation and vent the vapors to the outside air. 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.

Radon in Homes -

Radon also enters buildings from soil. 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. There are options available for homeowners to lower exposure to radon in their homes. For more information about radon and radon testing, visit MDH Indoor Air Radon webpages.

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Vapor Intrusion and Drinking Water

Municipal drinking water usually comes from deep wells or surface water. Vapor intrusion is often associated with contamination of shallow groundwater or soil.

  • Municipal drinking water is routinely tested for contamination to ensure that drinking water meets standards. 
  • If you use a private well for drinking water and your property is undergoing a vapor intrusion investigation, contact us for more information.

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Information about your sampling results and decisions made at residential and commercial 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.

For information about understanding your test results, see the MPCA Web page -  Understanding your vapor intrusion test results.

Information for people in residential buildings:

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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For more information

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

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

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Updated Friday, May 05, 2017 at 07:18AM