Western South Dakota's Only Ranch Station

South Dakota has highest average levels of radon in nation

Seth Tupper / South Dakota Searchlight
Bob Burns and his son Murray LaHood-Burns, of Earthorizons Inc., install a radon mitigation system in a Rapid City home on March 24, 2023.

STURGIS, S.D. – Donna Wright and her husband moved to the Black Hills in 2005 and built their home atop a mountain ridge overlooking the prairie, Bear Butte and the Black Hills near Sturgis.

It was a “dream come true,” until the couple realized they were being exposed to 20 times more radon than the amount deemed safe by the Environmental Protection Agency.

As an oncology nurse, Wright was aware of the risks of radon and its presence in the Black Hills. An invisible threat, the naturally occurring gas with no color, taste or smell is the second leading cause of lung cancer in the United States, and about 21,000 deaths are associated with it each year.

Formed when radioactive metals break down in rocks, soil and groundwater, radon can enter buildings through foundations, sinks, showers and toilets. It can be found in water or air, the latter being the most worrisome in terms of cancer risk.

The Wrights’ house had a radon level around 80 picocuries per liter. The average indoor reading in the U.S. is 1.3 pCi/L, and the EPA says levels exceeding 4 pCi/L are unsafe.

Sixty percent of homes tested in South Dakota have elevated radon levels, which is the highest rate in the nation, according to the American Lung Association.

The state also has the highest average reading of radon levels across the nation, according to a 2022 report from the association. According to the EPA, the average indoor reading in South Dakota is 9.8 picocuries per liter — over twice the recommended safety level.

The Wrights hired a radon mitigation expert to install piping and a fan in their home to better circulate the air. Now, their radon levels are “basically zero,” Wright said.

“You just have to be aware of where you’re at,” Wright said. “If you lived in a big city, you should be aware of smog. I think it’s just environmental awareness and knowing the environment you’re in here in South Dakota.”

Why is South Dakota so high?

Bob Burns, owner of Earthorizons Inc. in the Black Hills, has been working in radon mitigation for decades. He said it’s more likely than not that homes have high levels of radon, and although the EPA safety threshold is 4 pCi/L, he considers any reading above the average outdoor level of 0.4 pCi/L to be elevated.

“I would guess every house in South Dakota has an elevated radon level,” Burns said.

Radon risk in the state is particularly elevated in the Black Hills, where a ridge around the Black Hills is rich with minerals including some uranium deposits in the Edgemont and Elkhorn Creek areas. Rapid City sits on both sides of the ridge, which is known as the Dakota Hogback.

Colorado, Montana, North Dakota, South Dakota, Utah and Wyoming are among the highest-risk states for lung cancer from radon gas, according to the EPA. Radon concentrations are generally high in this area because uranium is concentrated in the granites and metamorphic rocks of the Rocky Mountains.

A map of geologic radon potential in the United States. The "high" potential includes all of eastern South Dakota and the ridge around the Black Hills. (Courtesy of USGS)
 A map of geologic radon potential in the United States. The “high” potential includes all of eastern South Dakota and the ridge around the Black Hills. (Courtesy of USGS)Burns said he’s seen homes in Rapid City with levels above 100 pCi/L — he’s even worked on a home that had a reading of 1,000 pCi/L in the Black Hills area.

Custer County has the highest average radon concentration with an estimated mean of 30.1 pCi/L — over seven times the EPA recommendation, according to the American Lung Association.

Of South Dakota counties that had at least 10 reported tests between 2008 and 2017, the lowest mean radon level was 4.9 pCi/L in Aurora County. Minnehaha County, with 1,920 tests, had an estimated mean radon level of 6.5 pCi/L.

“People in South Dakota talk to each other,” Burns said. “I think we have a lot of testing done, especially testing done in areas where radon is high.”

Lung cancer is SD’s leading cause of cancer deaths

Breathing radon for extended periods of time can pose significant risks, and those who smoke have an even greater chance of getting lung cancer when combined with radon exposure. Children and the elderly are also vulnerable.

Radon enters a home through cracks in walls, basement floors, and foundations, as well as water used for showers, dishwashing, and toilet flushing. Radioactive particles from radon become trapped in a person’s lungs when they breathe the gas, ultimately causing damage over time.

Signs of radon poisoning can closely resemble lung cancer, such as a cough that won’t go away, trouble breathing, blood in mucus, chest pains, wheezing or frequent respiratory infections.

According to the EPA, living in a home with South Dakota’s average level of radon is like “having 300 chest X-rays each year.”

"Radon is estimated to cause about 21,000 lung cancer deaths per year" (Courtesy of the Environmental Protection Agency) Drunk driving causes about 17,400; Falls in the home, 8,000; drownings, 3,900; and home fires, 2,800
 (Courtesy of the Environmental Protection Agency)In South Dakota, lung cancer is the leading cause of cancer deaths with a death rate of 36.2 per 100,000 residents. For context, prostate and breast cancer are the second and third leading cancer deaths in South Dakota at 19.1 and 18.9 deaths per 100,000 people, respectively.

South Dakota’s lung cancer death rate ranks 23rd among all states, according to the American Lung Association.

State offers free radon testing kits

Homeowners can check the radon levels in their homes with test kits or through an official inspection of their home. Such kits can be purchased at a hardware store for under $20.

The state Department of Agriculture and Natural Resources also provides 500 radon tests for free a year through its air quality program.

Test kits are shipped directly to the homeowner. After the sample is collected, the homeowner can ship the completed test to a lab for free analysis. DANR also provides technical assistance on how to test for and mitigate radon, said Brian Walsh, public affairs director for the department.

Graphic shows how radon can enter a home, including cracks in floors and walls, construction joints, gaps around service pipes and the water supply. (Courtesy of the Environmental Protection Agency)
 (Courtesy of the Environmental Protection Agency)Long-term tests are also available, which average out the highs and lows of reading levels across three months, painting a more accurate picture, Burns said.

Once someone detects radon in their home, they should hire a mitigation specialist, Burns said. South Dakota does not require mitigation specialists to be certified, though Burns is nationally certified for home and multi-family mitigation and is a member of the American Association of Radon Scientists and Technologists.

State requires seller disclosure

Mike Austad, owner of Dakota Radon Mitigation in Sioux Falls, is seeing an increase in people testing and hiring him to install radon mitigation systems in their homes. He typically sees radon levels between 8 and 10 pCi/L.

Austad is starting to see radon resistant homes “gain traction” in East River as well.

“There’s still room for more growth in that area of building in-phase radon resistant construction,” Austad said. “It doesn’t cost much, and I’ve been an advocate of that from the get-go.”

Despite high levels of radon across the state, South Dakota doesn’t have legal requirements to test homes or build “radon resistant” homes. Such homes use materials and “passive radon system” techniques that prevent radon from entering a home. All new homes built in Minnesota are required to be built radon-resistant since 2009.

South Dakota only has a law requiring sellers to disclose known radon levels in the sale of a home. It does not require radon testing and does not require landlords to disclose radon levels to tenants.

“Typically people say ‘no’ in that form, but they should say ‘don’t know’ because often ‘no radon’ is the wrong answer,” Burns said.

But Austad believes South Dakota is dealing effectively with the problem.

“I believe the word is out there and it’s getting more and more common,” Austad said. “You have professional real estate and home sales people who are disclosing radon information and are advising their clients to get tested now. In a way, maybe such laws wouldn’t be as effective or helpful as they would have been years ago.”

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