Map of Kentucky showing indoor radon potential
Geologically based indoor radon potential map of Kentucky. Map category breaks were converted from local customary units of picocuries per liter (1 picocurie per liter = 37 becquerels per cubic meter (Bq/m3)) and rounded upward to the nearest 10 becquerels per cubic meter to simplify the map legend. Credit: Haneberg et al., 2020,, CC BY 4.0

It sounds like the beginning of a joke: What do you get when you put a team of geologists and nurses in the same room? But the answer is no laughing matter for Kentuckians.

Although smoking itself is a well-known health risk—and Kentucky dances around the top spot for cigarette smokers in the United States—smokers who live in a home with radon gas exposure can be 10 times more likely to be diagnosed with lung cancer.

But how prevalent is radon in Kentucky homes? The first step to answering the question is understanding the underlying geology—the source of radon gas. In an innovative collaboration, the Kentucky Geological Survey (KGS) and the Bridging Research Efforts and Advocacy Toward Healthy Environments (BREATHE) research group at the University of Kentucky have created an interactive radon hazard map available to the public.

The map is web based and searchable and merges detailed geologic mapping, radon home test kits, and color-coded hazard values to help residents understand their risk to the clear, odorless, tasteless gas. The researchers hope the map will be a useful tool for both residents and public health experts.

Partnership Forged in Bedrock

The collaboration began about 5 years ago. The University of Kentucky published a news article on researchers in the School of Nursing working on radon exposure. A geologist at KGS (which is also affiliated with the University of Kentucky) saw the story, and his interest was immediately piqued.

“Well, you know, radon comes from rocks, and rocks don’t start and stop at county boundaries.”

In the original article, the radon map they were using showed risk at the county level. “Our geologist said, ‘Well, you know, radon comes from rocks, and rocks don’t start and stop at county boundaries,’” said Bill Haneberg, state geologist and director of KGS and lead author of a paper in GeoHealth that detailed the interactive radon mapping project.

Haneberg explained that Kentucky already has exceptionally detailed geologic maps. (“For so many years, the motivating factor for these great maps we have in Kentucky was coal,” he added.) “There was this phenomenal collaborative program between the U.S. Geological Survey (USGS) and the KGS,” he said. From 1960 to 1978, geoscientists mapped the entire bedrock geology of the state at a 1:24,000 scale, and the maps have all been digitized.

Geologists at KGS shared the maps with the BREATHE team. Ellen Hahn, director of BREATHE and a coauthor of the paper, was impressed with their detail and scalability.

“Our initial work was based on 1,000 indoor radon values in northern Kentucky,” Hahn said. The initial collaboration between KGS and BREATHE used this smaller data set and geologic mapping to look for any patterns. “We were looking for statistical correlations between the types of rock formation and indoor radon values that we had from that data set,” she noted. “We did indeed find interesting results from that.” For instance, homes built on limestone, dolostone, and some shales have higher indoor radon concentrations than homes on siltstone, sandstone, and surficial deposits.

Scaling Up the Project

From the northern Kentucky data set, the team then scaled up the project to the entire state. Hahn explained that two companies had been distributing and analyzing home radon kits in Kentucky for more than 20 years. She contacted those companies and asked for historical data, making sure that personal information was kept private—all addresses were changed to coordinates, for instance. In the end, the team ended up with more than 71,000 radon tests across the state.

“It turns out in Kentucky, the highest rate of potential is associated with Mississippian limestones.”

The team grouped the indoor radon tests located in a specific geologic formation to look at the values of measured radon. Using the 75th percentile of radon measurements, rock units were color coded for hazard. When a person clicks on the map, a box pops up containing information about the rock unit, measured radon levels, and number of radon kits tested for that formation.

“I think that map is quite cool. It’s really nice to look at, and I think it’s pretty accessible,” said Douglas Brugge, an environmental health professor and chair of the Department of Public Health Sciences at the University of Connecticut. He was not involved in the study. “I think what most people are going to want to do is look for where they live, they’re going to want to zoom in on the map for their locality and get a sense of risk in their area.”

“The highest potential may surprise a lot of people,” said Haneberg, explaining that Kentucky has a lot of uranium-rich, Devonian age black shales. “But it turns out in Kentucky, the highest rate of potential is associated with Mississippian limestones. In fact, if you look at that map, there’s a big red belt going around the edge of the Illinois basin—those are Mississippian limestones, including the same limestones that host Mammoth Cave.” Haneberg noted that Devonian shales, with all of their uranium, came in third.

Flyer explaining what radon is and how to determine risk in Fayette County, Kentucky

The EPA suggests an action level of 4.0 picocuries per liter, meaning that radon remediation should be done on homes that register those radon levels. On the map, the worst rock units for potential radon release were in excess of 16 picocuries per liter. Haneberg pointed out that the map is not a definitive measurement of the radon at an individual home, as that number is influenced by variations in geology and home construction.

Researchers said the map demonstrates the value of cross-disciplinary science. “I think environmental health hazards usually require people who are more on the physical sciences side and people who are on the public health, epidemiology side,” Brugge noted. Although geologists can focus in on the exposure to hazards, public health experts can link the exposure to health concerns and communicate risk to the public.

If the public can understand that the interactive map is a first step in understanding their exposure, then the efforts were successful, said Brugge. “If it motivates [residents] to do testing when they wouldn’t have done it, then that’s a good thing.”

Clear Communication and Collaboration

When communicating with the public, “I think it’s really important to distinguish between hazard and risk—it’s a subtle thing,” said Haneberg. Geologists look for hazards—what is the likelihood of this rock unit releasing radon? Risk, on the other hand, “involves the consequences” of those hazards, he explained.

That’s where the public health experts come in. “We bring the knowledge of disease and how it affects the body…how environmental exposures affect people’s risk of developing the disease,” Hahn noted. “We’re very familiar with prevention of disease through exposures.” Part of that prevention is behavior change—whether that is quitting smoking or adding radon remediation to a house.

The radon mapping and communication strategy saved approximately one premature lung cancer death and between $3.4 million and $8.5 million every year.

Hahn and her team have been working on how best to get radon risk information to the public. She said they targeted high-risk counties for their initial outreach efforts. “We invited the Cooperative Extension agents, the health department, and other professionals…to a lunch-and-learn—bring your lunch, and we’ll teach you something about radon.” Each participant got infographics, free radon test kits, and some presentation materials to go out into their communities.

In a related study, Hahn and her colleagues ran an economic analysis to assess the value of using geologic data to help communicate radon risk potentials in Kentucky. They wanted to understand how geologic maps may have reduced lung cancer by fostering increased testing and increased mitigation. “We were able to find that we actually save lives and money,” Hahn said.

They found that the radon mapping and communication strategy saved approximately one premature lung cancer death and between $3.4 million and $8.5 million per year.

—Sarah Derouin (@Sarah_Derouin), Science Writer


Derouin, S. (2021), Detailed geologic mapping helps identify health hazards, Eos, 102, Published on 27 July 2021.

Text © 2021. The authors. CC BY-NC-ND 3.0
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