Radon the #1 Silent Killer

HSS was awarded the bid for the US EPA VOC project in St. Louis Park, MN and the General Mills VOC project, along with numerous large commercial projects, multi-family and single-family projects in Minneapolis and St. Paul.

Large Multi-Family

Large Multi-Family

Single Family

Single Family



What is Radon?

Radon is a naturally occurring radioactive gas which comes from radium found in the ground everywhere. This gas collects in buildings and forms radon decay products which mostly attach to dust particles in the air. Inhalation of these radon decay products results in deposition of radiation energy (alpha particles) in surface tissues of the lung. This is the largest source of radiation dose to an average person and radon is a known cause of lung cancer in humans.

Radon is Known to Cause Lung Cancer in Humans

Radon is classified as a Class A known human carcinogen according to the World Health Organization's International Agency for Research on Cancer (IARC 1988). This classification is based on the strong evidence of lung cancers in underground miners. Data from 11 studies of radon-exposed underground miners show that about 40% of the 2,700 lung cancer deaths which occurred among 65,000 miners are due to radon according to the National Cancer Institute (NCI 1995). Among never-smokers, 70% of the lung cancer deaths are believed to be due to radon and 39% of the lung cancer deaths in smokers. While there are many differences in radon exposure conditions between mines and homes, it is notable that persons living in homes with radon above the EPA action level of 4pCi/L could accumulate radon exposures similar to underground miners. Miner studies show a consistent linear no-threshold relationship between lung cancer and radon exposure down to radon levels commonly found in homes. Epidemiology studies on residential radon exposures are consistent with expectations based on the linear model. Therefore, the National Cancer Institute indicates that 10% of all lung cancer deaths in the U.S. could be due to indoor radon exposures, 11% of lung cancer deaths in smokers and 30% of lung cancer deaths in never-smokers. When differences between mine and home exposures are taken into account, we find that exposures above 4pCi/L represent substantially greater risks than allowed for any other source of radiation exposure.

Radon Testing is Encouraged for All types of Homes in the U.S

While only about 8% of the homes in the U.S. have radon levels in living areas above the EPA action level of 4 pCi/L, these homes cannot be found without checking all homes. AARST recommends testing of homes, schools, public, and commercial buildings in high radon areas as the first priority.However, since high radon levels have been reported in all areas of the U.S. by radon testing companies, the second priority is to encourage testing of all homes. This could be done over time as part of routine inspections for real estate transactions.

The Duration of Radon Exposure Should be Considered Before Taking Action

The risk of lung cancer from radon is related to both the radon level and the length of time one is exposed. Consequently, if the exposure time is short, even large radon concentrations may not contribute to significant risk. Therefore, radon testing should be done in that part of a building where people spend the most time. Also, since lung cancer due to radon exposures may require several decades to occur, older people should not have as much concern for reducing radon levels as younger people. A family with young children living in a home for many years may gain a greater benefit by reducing their radon exposures.  (from AARST website)

 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 (see list of Major Radon Entry Routes below). 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.

 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).

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. 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.

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

Radon is colorless, odorless and tasteless. Therefore, 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 current and future radon levels for a home that has been remodeled, weatherized or had changes made to 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.   indoorair@health.state.mn.us

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.

Experienced radon mitigation professionals can install appropriate control systems. Contact MDH for information regarding radon mitigation.

Building a New Home?

MDH recommends that all new homes in Minnesota be built to include radon-resistant construction features that minimize radon entry into the home and make future radon problems easier to fix should they occur. It is more cost-effective to include radon-resistant features when building a home rather than retrofitting an existing home. If elevated radon levels are found after you move in, radon-resistant features can be easily activated to become radon reduction systems. Ask your builder if they are currently using radon-resistant construction techniques.

All newly built homes in Minnesota should be tested for radon after they are completed and occupied. Early detection of elevated radon levels can help protect the homeowner's financial interests if the radon problem is due to construction problems and can allow the homeowner to take appropriate actions to lower the radon level and protect the health of their family.