Vapor intrusion occurs when chemical vapors migrate from contaminated groundwater through the soil into the basements or foundations of buildings. Vapor intrusion can degrade indoor air, sometimes to the point of causing risks to human health. It is a form of environmental contamination that regulators and health officials have only recently begun to understand.
In Minnesota, the first significant case of vapor intrusion was discovered in St. Louis Park in 2007. See the St. Louis Park Solvent Plume page for more information about this case. The U.S. Environmental Protection Agency has indicated vapor intrusion is an emerging issue in environmental cleanup, and the Minnesota Pollution Control Agency (MPCA) expects to an increase in vapor intrusion cases in the coming years.
What are the health concerns?
Potential health risks from vapors in indoor air include eye and respiratory irritation, headache, and nausea. Long-term exposure can, in some cases, increase the risk of cancer. Health risks may be present even if there are no detectable odors. For more information on potential human health effects of indoor vapors, visit the Minnesota Department of Health Web site.
What are the pollutants of concern?
Usually vapors come from chemicals called volatile organic compounds (VOCs) in contaminated soil or ground water. VOCs are used in solvents and degreasers, and are often found in soil or groundwater at industrial sites where there were spills or improper disposal. In groundwater, VOCs are relatively stable, but at the water table they can assume a vapor phase (evaporate) and travel through overlying soils. Two specific compounds, perchlorethylene (PCE) and trichloroethylene (TCE), are often seen in vapor intrusion. These chemicals are commonly used in dry cleaning and degreasing.
Is vapor intrusion a new type of contamination?
In the past, contaminated sites were viewed in terms of their effects on groundwater, not their ability to contaminate indoor air. There is a better understanding of the potential associations between contaminated ground water and soil vapors due to improved investigative methods and detection technologies. As a result, environmental regulators have become aware that VOC-contaminated ground water may act as source for vapor intrusion at many sites -- even sites that were previously cleaned up, or where groundwater plumes are stable and contained.
What is the MPCA doing about vapor intrusion?
In 2009, MPCA staff began file reviews of active and closed remediation sites to determine which have potential for vapor intrusion. Those that score higher will receive field reconnaissance and sampling. Sites that show potential for vapor intrusion will be investigated and remediated.
While the issue of vapor intrusion at contaminated sites is relatively new, proven mitigation technologies are available. Sites that have vapor intrusion are typically remediated with vapor-extraction and treatment systems. If present inside buildings, vapors can be removed by installing in-home extraction systems similar to those used for treating radon.
Contacts For More Information
- Minnesota Pollution Control Agency
Remediation Division, 651-296-6300
- Minnesota Department of Health
Site Assessment and Consultation Unit, 651-201-4897 or 800-657-3908, email email@example.com