Radon is a naturally occurring radioactive gas.  Radon is tasteless, odorless, and colorless. It comes from the radioactive decay (breakdown) of radium, which comes from the radioactive decay of uranium.  Both radium and uranium are found in at least trace amounts in almost any kind of soil or rock. Granites, shales, and phosphates have higher than average concentrations of uranium.  As a result, they may produce higher concentrations of radon. However, elevated radon levels can occur even in areas with low concentrations of uranium in the soil or rocks. 

Radon is not chemically reactive with most materials.  Hence, it will move freely as a gas through the ground.  The first four radioactive isotopes formed as radium decays are polonium-218, lead-214, bismuth-214, and polonium-214.  They are commonly referred to as "radon daughters" or "radon progeny."  These short-lived isotopes are not gases but are chemically active solids.  They are present in any environment where radium was once found and, like radon, cannot be detected by human senses.

The earth is the source of all radon gas in our atmosphere.  Since radium and uranium concentrations vary throughout the earth's crust, radon concentrations will also vary in a geographic area.  The amount of radon gas that escapes into the atmosphere is dependent on the depth at which it is formed and the permeability of the surrounding earth.  Radon formed in the top 10 meters of soil and rock provides the largest component of radon entering the atmosphere.  Because they are metallic particulates, radon daughters formed in the soil will not escape.

The second most important contributor to atmospheric radon is from groundwater.  Underground radon is carried in groundwater and when this groundwater surfaces, most of the radon is released to the atmosphere.

Other sources of atmospheric radon are very small contributors and are largely due to human activities.  For example, there are radium-rich industrial by-products spread upon the earth, and sometimes construction materials are produced from raw materials that contain uranium or radium. 

Worldwide, over 2.5 billion curies of radon are emitted annually into the atmosphere.  Atmospheric dilution results in a typical outdoor level of between 0.2 and 0.7 picocuries per liter (pCi/l).  However, wide variations do exist. 

The problem occurs when radon and radon decay products (RDPs) are inhaled. When radon is exhaled, many RDPs are also exhaled, but some of the RDPs stay trapped in the lungs. As they undergo radioactive decay, they emit alpha particles. The alpha particles can strike sensitive lung tissue causing physical and/or chemical damage to the DNA. When alpha particles strike and damage a lung cell, the cell will either:

• Die, which seems like a bad thing, but new cells are generated to replace dead cells;
• Repair itself and heal; or
• Try to repair itself but do so incorrectly, possibly leading to the body forming cancer cells.

Not everyone who breathes radon will develop lung cancer. Your risk is determined by how much radon is in your indoor environment, how much time you spend in that environment, and whether you ever smoked. The only known health effect of radon is an increased risk of lung cancer. Exposure to elevated radon levels does not result in any warning symptoms like headaches, nausea, fatigue, or skin rashes. The only way to know whether you are being exposed to elevated radon levels is to perform a radon test.

The following national and international organizations support testing for radon and taking steps to reduce elevated radon levels to minimize the chance of getting lung cancer:

• American Lung Association
• American Medical Association
• Centers for Disease Control
• Environmental Protection Agency
• International Commission on Radiological Protection
• National Academy of Science
• National Council on Radiation Protection and Measurement
• U.S. Surgeon General
• World Health Organization

Additional health risk information is available in the U.S. EPA's Assessment of Risks from Radon in Homes and the National Research Council's consensus report titled The Health Effects of Exposure to Indoor Radon or the report summary.

For example, you can spend less time in the basement if levels down there exceed the guideline but levels on the first floor are acceptable. Ultimately, your best option is to take action to prevent or reduce how much radon is entering your home. This way you don't have to worry about where you spend your time in your home.

Some of the first steps you can take to reduce radon entry is to caulk and sealing entry points. You can caulk and seal the floor/wall joint; sump openings; cracks in the floor or walls; space around plumbing, wiring or ductwork; and/or openings at the top of a hollow block wall. Unfortunately, caulking and sealing is rarely adequate as a stand-alone mitigation option. To get guaranteed results, a trained contractor can be hired to install a radon mitigation system. Almost any radon level, regardless of how high it is, can be brought down to below the 4 pCi/L recommended action level.

Most radon mitigation systems are made of series of pipes and fans that remove radon vapors from under your foundation and exhaust them above the roof where it's safe. This type of system is also referred to as an active soil depressurization system because it reduces the pressure under the house, so radon gas is no longer being pushed in through openings in the foundation. Radon mitigation systems generally start with a four-inch plastic pipe that goes down through the foundation floor and runs up and out of the house as shown here in the picture and linked video. A small in-line fan is attached to draw radon vapors from under the foundation or slab into the pipe, then up and out the pipe at the roofline.

Radon mitigation systems designs vary from home to home. Some contractors take advantage of existing sump openings and fit them with a special cover, then run the PVC pipe down into that hole. Other contractors may drill a four-inch hole through the cement floor and dig out a pit about the size of a five-gallon pail. Others may tie into an existing drain tile. When dealing with crawlspaces, a plastic vapor barrier is needed. The barrier is needed for the system to capture and pull the radon vapors from under the plastic barrier and prevent them from entering the home. Most systems are designed for the pipe to exit the interior of the house just above ground level. A fan is mounted on the outside of the home, then the exhaust stack runs up the side or back of the house to just above roof level, exhausting the radon gas away from any windows or openings that could draw the radon back into the home.

Nationally the price of a home radon mitigation system ranges from approximately $500 to $2,500. Here in Michigan a radon mitigation system generally costs between $800 and $2,500, depending on where you are in the state and who you hire. The systems can usually be installed in a day or less, and a reputable contractor will provide a guarantee that the system will achieve results below 4 pCi/L. Often the systems can achieve results below 2 pCi/l.

Michigan does not license or regulate radon testing and mitigation contractors. So, a person who is trained and certified by one of the two national organizations that offer certification for testers and mitigators, should be used. The National Radon Proficiency Program or the National Radon Safety Board both maintain a list of certified contractors on their websites. A list of certified contractors can also be obtained from your local health department, or by calling the Michigan Department of Environment, Great Lakes, and Energy (EGLE) Indoor Radon Program at 800-RADON GAS (800-723-6642).

Radon occurs naturally in soil and rock and can enter buildings through openings in the foundation floor or walls. Long-term exposure to elevated indoor radon levels can increase your risk of lung cancer, and since any home could have a problem, all homes should be tested.

The good news is, when elevated radon levels are found, they can be reduced, and new homes can be built using radon-resistant construction techniques. If you are building a home, talk to your builder about including a passive radon control system in the construction process. It is an inexpensive addition to the total cost of your new house and is an easy way to help reduce the risk of a radon problem. Currently, the Michigan Residential Building Code requires radon-resistant construction techniques in nine Michigan counties: Branch, Calhoun, Cass, Hillsdale, Jackson, Kalamazoo, Lenawee, St. Joseph, and Washtenaw. However, elevated radon levels have been found in every Michigan county and radon-resistant construction techniques are recommended for all homes statewide.

If an elevated radon level is found after the home is completed, the problem can still be fixed. Your passive radon mitigation system can be "activated" to provide further radon reduction. This is accomplished by adding an in-line fan to the existing system, and this simple upgrade will almost always achieve results that are well below the U.S. Environmental Protection Agency guideline of 4 picocuries per liter of air (4 pCi/L).

Radon-Resistant Construction Is Easy and Inexpensive!

There are simple techniques specific to radon-resistant construction, and when combined with other good building practices, the process of building a radon-resistant home is relatively easy and inexpensive. Special skills are not required to perform this type of work. These techniques and materials are commonly used in the construction of a new home.

Simple Steps

• Gas Permeable Layer - Install at least a 4" layer of clean gravel or aggregate beneath the slab or flooring system to allow soil gases to move freely beneath the home.
• Impermeable Layer - Cover that layer with a vapor barrier (plastic or polyethylene sheeting) to help prevent radon and other soil gases from entering the home.
• Vent Pipe - Run a 3-inch or preferably a 4-inch PVC pipe routed vertically (i.e., no turns or elbows) through the middle of the house from the gas permeable layer up through the roof.
• Caulking and Sealing - Caulk and seal all openings in the foundation floor or walls (including the slab perimeter) with a polyurethane caulk to reduce the potential for soil gas entry.
• Junction Box - Install an electrical box (outlet) in the attic in case a fan is needed to reduce radon levels further.

The average cost of installing a passive radon control system may be $350-$500. If you're building a home, make sure your builder uses these techniques to make your new home radon-resistant! Then test it to determine the radon levels, and if there's still a problem, simply have the system activated by installing a radon fan. Though builders are not required to use radon-resistant techniques in homes built in some counties, you may want to request that the builder incorporate these techniques during construction of your new home.

Benefits of a Passive Radon Mitigation System:

• The techniques are simple and inexpensive.
• Typically reduces radon levels by about 50%.
• The system may reduce concentrations of other soil gases as well.
• The system can increase energy efficiency.
• The system may help control moisture and sometimes even eliminate that "musty smell" common in basements.

If elevated radon levels are found, the passive system can easily be upgraded to an active system that will provide further radon reduction.

For more detailed information about radon-resistant new construction, check out the following:

• RRNC Essential Components Inspection Form
• ANSI-AARST National Standards
• Rough-In Of Radon Control Components In New Construction Of 1 & 2 Family Dwellings And Townhouses
• Reducing Radon in New Construction of 1 & 2 Family Dwellings and Townhouses – Rev. 5/23
• Soil Gas Control Systems in New Construction of Multifamily, School, Commercial and Mixed-Use Buildings – Rev. 5/23
• EPA's Radon Website

As is the case with homes, however, the only way to know whether a building has elevated radon levels is to test that building. Differing soils and geology, construction factors, and occupancy patterns can result in significantly different radon levels from room to room and from building to building, even in the same general locale. All buildings should be tested.

Since schools may be the second largest contributor to a child's radon exposure (or to teachers or staff), the U.S. Environmental Protection Agency (USEPA) recommends that radon testing be conducted at all school buildings and that action be taken to reduce elevated radon levels.

Surveys have shown that radon levels can vary significantly from room to room within a school.  ANSI/AARST MA-MFLB-2023 Protocol for Conducting Measurements of Radon and Radon Decay Products in Multifamily, School, Commercial and Mixed-Use Buildings requires testing in all frequently occupied rooms that are in contact with the ground. If a room is found to have a level greater than the USEPA guideline of 4 picocuries per liter (4 pCi/L), additional testing should be done to confirm the problem. If elevated levels are verified, action should be taken to reduce the radon level. 

Additional helpful resources include:

ANSI/AARST CC-1000-2018-0523 Soil Gas Control Systems in New Construction of Multifamily, School, Commercial and Mixed-Use Buildings – Rev. 5/23

A workplace would be the second largest contributor for much of the adult population, and as such, it would be a good idea to test for radon and reduce elevated levels in the indoor work environment. The procedures outlined in ANSI/AARST MA-MFLB-2023 Protocol for Conducting Measurements of Radon and Radon Decay Products in Multifamily, School, Commercial and Mixed-Use Buildings should be used for large buildings as well.

Workplace mitigation requirements are governed by Occupational Safety and Health Administration (OSHA), unless they are a Nuclear Regulatory Commission (NRC) licensee. Under OSHA, the radon limit is 100 pCi/L. If the entity is licensed by the NRC, the radon limit is 30 pCi/L.

Additional helpful resources include: 

ANSI/AARST CC-1000-2018-0523 Soil Gas Control Systems in New Construction of Multifamily, School, Commercial and Mixed-Use Buildings – Rev. 5/23

The Michigan Department of Environment, Great Lakes, and Energy recommends that elevated indoor radon levels be treated first as a soil gas problem, using conventional radon reduction techniques to lower those levels. Radon in water testing need not be routinely conducted and would be recommended only if the conventional techniques are not successful. Then, the homeowner may wish to test the water to determine whether it is contributing to the radon in air.

For more information on radon in water and public water standards, contact the USEPA Drinking Water Hotline (800-426-4791) or see the National Academy of Sciences, Risk Assessment of Radon in Drinking Water. Additional resource information can be found at Kansas State University's National Radon Program Services website.

• Risk Assessment of Radon in Drinking Water - Published by the Committee on Risk Assessment of Exposure to Radon in Drinking Water, Board on Radiation Effects Research, Commission on Life Sciences, National Research Council, and National Academy Press
• Radionuclides Rule - U.S. EPA, Drinking Water Requirements for States and Public Water Systems