Radon is a naturally occurring, invisible and odorless gas released from the decay of radioactive metals like uranium found in soil, rocks and groundwater. According to the Environmental Protection Agency, it’s also the second-leading cause of lung cancer in the U.S., and claims more than 20,000 lives annually. Homes are a major source of radon exposure which testing kits can be used to monitor and determine whether to do mitigation by increasing ventilation or sealing foundation cracks.
But it turns out that even relatively low levels of radon exposure can be dangerous, according to a new study funded by the EPA and led by researchers at Oregon State University. They found an increased risk for developing another kind of cancer — childhood leukemia — in children in more than 700 counties in 14 states, even at average levels well below the EPA’s own established guidelines for when to do radon mitigation.
Joining us to share more is the study’s lead author, Matthew Bozigar, an environmental epidemiologist and assistant professor in the college of health at OSU.
Note: The following transcript was transcribed digitally and validated for accuracy, readability and formatting by an OPB volunteer.
Dave Miller: From the Gert Boyle Studio at OPB, this is Think Out Loud. I’m Dave Miller. We turn to radon now. It’s been called the “Silent Killer” for a reason. The naturally occurring, invisible and odorless gas is the second leading cause of lung cancer in the U.S., claiming more than 20,000 lives every year. But a new study, led by researchers at Oregon State University, found that radon could also be associated with childhood leukemia. Most significantly, the study found a correlation between radon and leukemia even at levels well below the EPA’s current guidelines for when to do radon mitigation.
Matt Bozigar is the lead author of the study. He is an environmental epidemiologist and an assistant professor in the College of Health at OSU, and he joins us now. It’s great to have you on the show.
Matthew Bozigar: Thanks. It’s a pleasure to be here.
Miller: What is radon?
Bozigar: As you mentioned, radon is this invisible, odorless, tasteless gas, and it exists as part of a decay chain from uranium. It eventually decays through many different elements, including radon, and then polonium, for example, and ends up finally at a stable form of lead. Radon and uranium – its parent material – are more common in certain types of soils and rock, namely granite. So places where there is that material under homes starts to present a source of, essentially, radioactivity, to homes. It can get into homes through cracks in the foundation, especially if you have basements. Homes can concentrate radon gas. And from there, it starts to decay, and that’s where the health risks start.
Miller: What was your personal motivation for looking into the links between radon and cancer?
Bozigar: It is personal. It started for me when I had a cousin who had brain cancer, was diagnosed in his twenties, and noticed a few other brain cancers and other odd types of cancers that had happened to … diagnosing people that were under the age of 30. And fast forward a few years – I was not an epidemiologist at that time, I hadn’t gone through the training that I now have – and two other cousins and two different families also were diagnosed. One with a brain tumor and another with Non-Hodgkin lymphoma. And started to ask around, and to see, is this something that’s happening in this community – I’m from Portland, I went to Grant High School – and why do I know so many people that are getting these early age cancers? Is this normal? And that really started me going all in on trying to understand, what is it about Portland’s environment that is potentially influencing these cancers?
We know that genetics only explain a small proportion. So once we were getting outside my family, I was thinking, as an environmental epidemiologist, I’m very interested in what could be causing this. And one of the first things is that Portland is high in radon. And so that started a line of research.
Miller: What data did you rely on for this study?
Bozigar: This study relies on a national data set. The cancer data came from the National Institute of Cancer’s Surveillance, Epidemiology, and End Results Program – the SEER database. That consisted of annual diagnostic counts of childhood cancer cases in 727 counties in the U.S. And then our radon data was from an advanced statistical model that some of the other members on our team had built recently. And that model was also able to estimate radon at the county level annually.
So we looked at associations between average basement radon levels and cancer diagnoses in 727 counties in the U.S., from 2001 to 2018.
Miller: And what did you find, broadly, when you looked at those two things – county level average radon in basements, and county level cancer diagnoses in children?
Bozigar: We found that in counties that had higher average basement radon levels, that there were essentially more diagnoses of childhood leukemia cases in those counties. So we looked at that relationship a few different ways, in a few different statistical analyses, and the results were consistent. The results were also consistent for both boys and girls, with males and females.
Miller: How do you think about correlation and causation when you’re doing a study like this?
Bozigar: I think that’s a really important point for this study, is that this is a type of study that’s a hypothesis-generating study. In our field, it’s known as an ecological study, because our unit of analysis is the county. So if we were to drill down further, and really look at the cancer cases that were diagnosed in those counties each year, we don’t know for certain what the radon levels were in those particular homes.
Miller: And that’s an important point, I think, because what I’ve always heard over the years is, there could be a huge variation in radon levels from home to home, both because of whatever rubble is beneath those homes, but also how they’re constructed, and how ventilation works. But it made me wonder how much we can take in terms of meaningful conclusions, if we’re looking at the county level, for something that is so different from house to house. What can it tell us and what can’t it tell us?
Bozigar: Yeah, it’s a good question. So, we know that in counties that have higher average radon levels, though, there are many homes that are pulling up that average. They’re contributing to a higher level overall. But yes, this study can only assess associations by design. It does present us with a starting point, to give us a rationale to do more research on this subject. But also, when we design a study like this, if we find an association, it’s typically the tip of the iceberg. These types of studies, because they are unable to look at individual relationships, tend to have attenuated relationships … to where it might seem like there might not be a relationship. But when we do find something, it is usually indicative of something larger.
Miller: What do you think it would take, in terms of the future studies, for you to say the federal government should lower the level at which it says you should mitigate, you should put fans in to blow radon gas above and away from the house. What would it take for you to actually want the federal government to change its guidelines?
Bozigar: That’s a great question, and I think we are in a moment in researching radon and the health effects of radon, where it is resurgent. Radon had been studied extensively in the 70s, 80s, and 90s in miners, so the adult male population, typically, in the healthy adult male population.
Miller: Just to be clear, in case people missed the last time, you’re not talking about young people, you’re talking about people whose job it is to mine stuff.
Bozigar: Correct. Yes. They’re under the ground, deep in the earth, mining different materials. So in those populations, they found pretty conclusive evidence that it’s causing lung cancer. So radon is causing lung cancer in that population, but then the studies fell off, after they more cursorily looked at some of the other population groups, but not necessarily in super robust ways. So, 30, 40 years later, now, we have all these new data streams. We have these fancy statistical models, as I mentioned, and it’s starting to give us new opportunities to look at different populations, groups such as children. We really haven’t had a good handle on how radon gas decay may be affecting children, and women, and people trying to have children.
As for what it would take for the EPA … we need more evidence. There’s a shockingly low quantity of evidence on radon and non-lung cancers. So that’s part of the gap that our team is trying to fill. And I know there’s other teams across the nation and across the world that are currently looking at this in the last five years. Really, a big uptick in radon research.
Miller: We’re talking about a childhood cancer that I guess was not initially associated with radon exposure. Are there other illnesses that you think should be added to the list of concerns?
Bozigar: Sure, and I want to clarify, too, that this is just in the U.S. that we’ve been talking about finding this for the first time. There was a study in Iowa before this, that found a suggestive association potentially, but it didn’t have enough people to truly say for certain. But in Europe – and in other places but particularly Europe – there’s been some recent meta-analyses or analyses of many studies on the topic of radon in childhood cancer. And they have found … they’re starting to find a signal, this is very recent. So our study actually adds to that body of evidence.
I have collaborators at the University of North Carolina, Chapel Hill, for example, talking about other potential diseases that found a relationship with stroke incidence. Radon being linked with incident stroke in a cohort of women, a national cohort of women. There’s a lot of work being done in places like the University of Kentucky that are looking at, I believe, dementia, and other outcomes. And radon has recently been linked with breast cancer and skin cancer.
So I think it speaks to the toxicity of the type of radiation that radon emits, and that’s particularly damaging to tissue type of radiation, which is known as alpha particle radiation. It’s essentially shooting off a little nuclei, helium nuclei to two protons and two neutrons, at high energy. And if that hits, if it’s near a bodily cell, if it hits DNA, it can cause a double-strand rupture and it is associated with various genetic mutations and deletions which are very, very toxic to the body … in the sense that they are associated with the beginnings of carcinogenic and other types of disease processes.
Miller: Matt, thanks very much.
Bozigar: Thanks a lot.
Miller: Matt Bozigar is an environmental epidemiologist and assistant professor in the College of Health at Oregon State University.
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