Radon in Minnesota Homes

Download a printable version of the Radon Brochure (PDF:755KB/15 pages)

The Minnesota Department of Health (MDH) provides information on radon and how to protect your family's health. The U.S. Surgeon General, the U.S. Environmental Protection Agency (EPA) and MDH recommend that every Minnesota home be tested for radon.

In Minnesota there are only regulations for new construction, so it is up to homeowners to decide for themselves how much radon is acceptable in their home. The good news is, homeowners can act to lower the amount of radon in their home and reduce the risks to their family.

What is radon?

Radon is a naturally occurring radioactive gas, that means it continuously decays and releases radiation. It is produced from minerals in soil, such as uranium and radium. It is colorless, odorless and tasteless.

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Why is radon important?

The U.S. Environmental Protection Agency estimates that each year 21,000 people die of lung cancer as a result of being exposed to elevated levels of radon. Radon is the second leading cause of lung cancer for smokers and the leading cause of lung cancer for non-smokers.

Although radon is present throughout the environment, radon levels indoors are generally higher which increase the risk of cancer.

Why is radon a common problem in Minnesota Homes?

Much of the soil in the Upper Midwest contains widespread uranium and radium. These minerals continuously break down to release radon gas. Therefore, Minnesota's geology provides an ongoing supply of radon.

In addition, a large percentage of Minnesota homes have elevated levels of radon in the indoor air because of how they are built and how they operate in our climate. One important factor is that many Minnesota homes have basements that are uses as living spaces.

MDH estimates that about one in three (1/3) Minnesota homes have enough radon to pose a significant risk to the occupants' health over many years of exposure.

How does radon enter a home?

Radon, because it is a gas, is able to move though spaces in the soil or fill material around a home's foundation. Minnesota homes tend to operate under a negative pressure - this is especially true in the lowest portions of the home and during the heating season. This negative pressure acts as a vacuum (suction) that pulls soil gases, including radon, into the lower level of the structure. Some causes of home vacuum are:

• Heated air rising inside the home (stack effect).
• Wind blowing past a home (downwind draft effect).
• Air used by fireplaces, wood stoves, and furnaces (vacuum effect).
• Air vented to the outside by clothes dryers and exhaust fans in bathrooms, kitchens, or attics (vacuum effect).

Radon can enter a home through the floor and walls -- anywhere there is an opening between the home and the soil. Examples of such openings include dirt floor crawl spaces, unsealed sumps, cracks in slab-on-grade floors, utility penetrations, and the tiny pore spaces in concrete block walls. A basement, of course, provides a large surface area that contacts soil material.

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Major Radon Entry Routes

1. Cracks in concrete slabs.
2. Spaces behind brick veneer walls that rest on uncapped hollow-block foundations.
3. Pores and cracks in concrete blocks.
4. Floor-wall joints.
5. Exposed soil, as in a sump or crawl space.
6. Weeping (drain) tile, if drained to an open sump.
7. Mortar joints.
8. Loose fitting pipe penetrations.
9. Open tops of block walls.
10. Building materials, such as brick, concrete, rock.
11. Well water (not commonly a major source in Minnesota homes).

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What happens after radon gets into the home?

Once radon enters a home it moves freely throughout the indoor air and people can breath it into their lungs where it can cause cell damage that may lead to lung cancer. Understanding how it distributes through the home environment can help explain why timing and location are important factors to consider when conducting a radon test.

The level of radon is often highest in the lower part of the building. Radon moves through a house by diffusion and natural air movements and it can be distributed by mechanical equipment such as a forced-air ventilation system. As radon moves away from the home's foundation or other entry points, it mixes (and is diluted) into a greater volume of air. In addition, more dilution often occurs in the upper levels of the home because there is more fresh air ventilation there.

Greater dilution and less house vacuum may also occur when the house is more open to the outdoors during the non-heating season. This generally results in lower indoor radon levels in the summer compared to the winter.

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How can I find out if my home has a radon problem?

A radon test is the only way to find out how much radon is in your home. Performing a radon test on your own is easy, inexpensive, and can be done privately. Every home is unique due to its local soil, construction details, maintenance and degree of depressurization. Therefore, test results from nearby homes cannot be relied upon to predict the radon level in another home. Likewise, previous test results may not reflect the current and future radon levels for a home that has been remodeled, weatherized or had changes so its heating air conditioning or other ventilation systems such as exhaust fans.

The MDH recommends that all Minnesota homeowners test their homes for radon. The results of a properly performed radon test will help homeowners determine for themselves if they need to take further action to protect their family from the health risks of radon in the home.

Contact the MDH Indoor Air Unit for more information on where to obtain low cost radon test kits, the types of test kits, how to perform tests properly and how to interpret the test results.

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How can I protect my family from radon?

A number of steps can be taken to lower the amount of radon in a home. A quality radon reduction (mitigation) system is often able to reduce the annual average radon level to below 2 picoCuries per liter (see Minnesota Radon Testing and Use of Test Results for discussion of radon levels and health risks). Experienced radon mitigation professionals can install appropriate control systems. Contact MDH for information regarding radon mitigation.

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For questions about this page or indoor air quality, please contact the Indoor Air Unit at health.indoorair@state.mn.us, 651-201-4601 or 800-798-9050.