What is radon?
Radon is a colorless, odorless, tasteless radioactive gas that is formed by the breakdown of uranium in the earth. When inhaled, the radioactive particles can damage the cells that line the lungs.
Long-term exposure to radon can lead to lung cancer. The U.S. EPA attributes more that 21,000 lung cancer deaths each year to radon, making it a serious health concern for all Americans.
Where does radon come from?
Most often, radon comes from the soil. Radon is formed by the natural breakdown of uranium, which is found in nearly all soils. Uranium is an unstable element, so it continuously decays until it forms a stable element — lead. Along the way, it forms radium, which disintegrates into radon, a radioactive gas.
How does radon enter a home?
Because radon is produced in the ground, it is present nearly everywhere. Soil is porous, so radon and other soil gases are able to move up through the dirt and rocks and into the air we breathe.
Without proper ventilation, radon can accumulate in indoor spaces, including your home, office, school, etc.
Two factors that determine how much radon will accumulate are pathways and air pressure. Because these factors differ from home to home, indoor radon levels vary from home to home.
Pathways are routes that gasses use to enter your home (openings between the soil and the home).
Radon can enter your home through the following pathways:
Cracks in concrete slabs
Uncapped hollow-block foundations
Pores and cracks in concrete blocks
Weeping drain tile (if drained to an open sump)
Exposed soil (in a sump or crawl space)
Loose-fitting pipe penetrations
Building materials (brick, concrete, rock, etc.)
Homes generally operate under a negative air pressure, especially during the heating season. The air pressure inside your home is typically lower than the surrounding air and soil, creating a vacuum that pulls soil gases into the home through the pathways. While the ground around the home may be frozen or soaked by rain, the gravel and soil underneath the home remain warm and permeable, attracting radon gas from the surrounding soil.
Factors that contribute to a home’s air pressure changes include:
Stack effect – Warm air rises to upper portions of the home and is replaced by cooler, denser outside air (some of which comes from the soil).
Down wind draft effect – Strong winds create a vacuum on the downwind as they blow past a home.
Vacuum effect – Combustion appliances (furnaces, hot water heaters, fireplaces, etc.), exhaust fans, and vents can remove a significant amount of air from a home. As indoor air is exhausted, outdoor air enters the home to replace it. This replacement air often comes from the soil underneath the home.
In general, any time air enters a home from the underlying soil, radon can come along with it.
What types of homes are most prone to radon exposure?
Any home can have a radon problem, regardless of foundation type.
A basement provides a large surface area in contact with the soil material. Radon can enter through cracks in the concrete, floor-to-wall joints, control joints, etc. Exposure to radon can be especially high for people who use their basements as a living space.
Like basements, homes with slab-on-grade foundations have many openings that allow radon to enter.
Homes with crawl spaces (vented and sealed) can also have elevated radon levels. Radon-laden soil gases can be drawn into the home due to negative air pressure vacuums.
Where is your greatest exposure to radon?
Radon is present everywhere, and there is no known safe level. Although radon is present outdoors, your greatest risk of exposure is where it can accumulate (indoors) and where you spend most of your time (at home). Radon can accumulate in your home whether it is old or new, drafty or well-insulated, regardless of foundation type.
Why is radon a concern?
The primary concern of radon exposure is the risk of developing lung cancer. Radon is the number one cause of lung cancer among non-smokers and the second leading cause of lung cancer among smokers (after tobacco). Luckily, this risk can be minimized through awareness and testing.
Radon is an unstable atom and breaks down into a family of elements (radon decay products). When you breathe, you will inhale both radon and radon decay products. While the radon atoms are exhaled, the radon decay products stick to the lung tissue. Radon decay products can further break down, irradiating the lung tissue and causing cell damage.
When radon and radon decay products break down, alpha particles are released. The alpha particles from the decay products are of concern because they can be released while the decay products are in the lungs. Cells in the lung do not have a thick protective coating, making them susceptible to damage from alpha particles.
When an alpha particles hits a lung cell, the cell may either die or suffer DNA damage. The cancer-suppressant gene can be impacted and cause the cell to lose its defense against cancer. This defect can be passed on to new cells, increasing the potential for lung cancer.
How likely is radon to cause lung cancer?
The potential for radon-induced lung cancer is a function of the amount of exposure (alpha particle hits), length of exposure (time), and smoking history. Prolonged exposure to low levels of radon is equally as dangerous as short exposure to high levels of radon. Because our bodies have no threshold for radon exposure, no level is considered safe. The only safe level of radon exposure is when there is no radon.
According to the EPA, “At EPA’s action level of 4 pCi/L, a smoker’s risk of lung cancer is about 5 times the risk of dying in an auto accident, and if you’ve never smoked, equal to the risk of dying in an auto accident. The U.S. Surgeon General and EPA strongly recommend that all homes be tested for radon.”
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