Radon in Minnesota Homes
The Minnesota Department of Health (MDH) provides information on radon and how to protect your family's health. MDH also recommends that every Minnesota home be tested for radon.
What is radon?
Radon is a colorless, odorless radioactive gas that seeps up from the earth. When inhaled, it gives off radioactive particles that can damage the cells that line the lung.
Long term exposure to radon can lead to lung cancer. In fact, over 21,000 lung cancer deaths in the US each year are from radon, making it a serious health concern for all Minnesotans.
Where does radon come from?
The soil. Radon is produced from the natural decay of uranium that is found in nearly all soils. Uranium breaks down to radium. As radium disintegrates it turns into radioactive gas...radon. As a gas, radon moves up through the soil and into the air you breathe.
Where is your greatest exposure to radon?
While radon is present everywhere, and there is no known, safe level, your greatest exposure is where it can concentrate-indoors. And where you spend most time-at home. Your home can have radon whether it be old or new, well-sealed or drafty, and with or without a basement.
How serious a problem is radon in Minnesota?
High radon exist in every state in the US. In Minnesota, one in three homes has radon levels that pose a significant health risk, and nearly 80% of counties are rated high radon zones. Some factors that further contribute to Minnesota's high radon levels include:
- Minnesota's geology produces an ongoing supply of radon.
- Minnesota's climate affects how our homes are built and operate.
How does radon enter a home?
Since radon is produced from soil, it is present nearly everywhere. Because soil is porous radon gas is able to move up through the dirt and rocks and into the air we breathe. If allowed to accumulate, radon becomes a health concern.
Two components that affect how much radon will accumulate in a home are pathways and air pressure. These components will differ from home to home.
- Pathways are routes the gas uses to enter your home and found anywhere there is an opening between the home and the soil.
- Air pressure between your home's interior and the exterior soil is what helps to draw radon gas into the home via pathways.
Radon's Pathways into your home
- Cracks in concrete slabs
- Spaces behind brick veneer walls that rest on uncapped hollow-block foundations
- Pores and cracks in concrete blocks
- Floor-wall joints
- Exposed soil, as in a sump or crawl space
- Weeping (drain) tile, if drained to an open sump
- Mortar joints
- Loose fitting pipe penetrations
- Open tops of block walls
- Building materials: brick, concrete, rock
- Well water (not commonly a major source in Minnesota homes)
Air pressures in your home
Minnesota homes commonly operate under a negative air pressure, especially during the heating season. What this means is that the air pressure inside your home is typically lower then the surrounding air and soil, and this creates a vacuum that pulls soil gases, such as radon, into the home via pathways. Even if the ground around the house is frozen or soaked by rain, the gravel and disturbed ground underneath the house remains warm and permeable, attracting radon gas from the surrounding soil.
Other factors also contribute to air pressure changes in a home, including:
Down Wind Effect
|As warm air rises to the upper portions of a home, it is displaced by cooler, denser outside air. Some of that displaced air comes from the soil.||Strong winds can create a vacuum as they blow over the top of the home.||Combustion appliances like furnaces, hot water heaters and fireplaces, as well as exhaust fans and vents, can remove a considerable of air from a home. When air is exhausted, outside air enters the home to replace it. Some of this replacement air comes from the underlying soil.|
What happens after radon gets into the home?
Radon levels are often highest at the entry point-typically in the lower part of a building. As radon gas moves upward, diffusion, natural air movements and mechanical equipment (such as forced-air ventilation system) distribute the radon through the home. Radon gas becomes more diluted in the upper levels of the home because there is more fresh air for it to mix with.
Greater dilution and less house vacuum effect occur when the house is more open to the outdoors, as during the non-heating season. This generally results in lower indoor radon levels in the summer compared to the winter.
Understanding how radon moves through the home environment helps to explain why timing and location are important factors to consider when conducting a radon test.