Reality check: How much of a danger is radon, anyway? Here’s the data

Since I started doing these data columns in 2020, one important source for topic ideas has been readers like you. I’m not able to address all of those ideas, or even most of them, but I do my best to make sure this column reflects the audience’s interests frequently.

Today’s column is one such example. Reader Rich Mouritsen writes: “Hi Andy. Suggestion for a data article… Radon. It’s a craze going through my neighborhood right now. Personally, I’m skeptical of how big of a factor it is for a non-smoker.” And I appreciate Rich’s confidence in me to get to the truth of the matter!

Luckily, radon happens to be a subject I know a little bit about. You see, my dad started a home inspection business over 20 years ago, and recently handed it down to my little brother once the firstborn (me) disappointed the family by going into a dismally un-lucrative journalism career. In full disclosure, this column is going to pull a bit from those family conversations, but, in typical Andy fashion, mostly from the peer-reviewed scientific research published on the matter.

What is radon?

Radon is one of the elements in the periodic table you saw in high school, near the bottom of the chart. In our world, it’s a colorless, odorless gas that is a byproduct of the radioactive decay of the trace amounts of uranium and radium found in soil and rocks.

The gas is everywhere, but thanks to its density compared to normal air, it tends to sit in either the soil it came from or relatively inclosed spaces. Mines usually have a ton of radon, but some seeps into houses and other buildings through cracks in foundation floors or walls. The two largest determining factors on how much radon is in an individual home seem to be the composition of the soil it stands on and the leakiness of the home itself.

Once inside your home, radon continues to radioactively decay, and that’s where you get problems. If you inhale it, it’s going to shoot alpha radioactive particles at your lung cells. That increases the likelihood of DNA damage in those cells, which increases the chances of a mutation that will cause cancer.

How do we know radon causes lung cancer?

So that all makes sense in theory. But how do we know radon causes lung cancer in practice?

The first place scientists tested that theory was in miners. These weren’t coal mines, but other kinds of mines where dust shouldn’t have led to lung issues. But lung cancers were still prevalent: a pool of 11 studies reported by the World Health Organization found collectively that for every year a person worked in a high-radon mine, they were about 5% more likely to get lung cancer.

Most of us, however, are not miners. What about us? There, it depends on how much radon has seeped into any given house.

Radon densities are measured in two different units. Internationally, it’s Becquerels per cubic meter (Bq/m³), which counts how many radon particles decay per second per cubic meter — pretty logical. In the United States, because we’re special, we tend to measure it in picoCuries per liter (pCi/L) — which has a more complicated derivation based on one gram of radium. One pCi/L approximately equals 37 Bq/m³; 100 Bq/m approximately equals 2.7 pCi/L.

The WHO again pooled studies to try to find out how radon impacts regular home dwellers. In 2009, they pooled 22 studies which included about 12,000 people with lung cancer and 21,000 without it across Europe, North America and China. Those studies then asked: how high were the radon levels in their homes? Participants had to have lived in their home for at least 15 years; on average, the researchers had 23 years of at least approximate radon history for each participant.

In the end, the data showed that for every additional 100 Bq/m³ (or 2.7 pCi/L) a person was exposed to in their homes during their life, they had an extra 20% chance of lung cancer. That result didn’t seem to vary based on a person’s gender, or, critically, their smoking history. Smokers are much, much more likely to get lung cancer in general, of course, but everyone seems to be impacted pretty equally by radon’s radioactive ways. That makes sense.

That leads to an estimate that radon is responsible for about 15,000 to 21,000 lung cancer deaths per year in America, or about 10-14% of lung cancer deaths annually. Smoking is the leading cause of lung cancer, but radon is No. 2.

What’s the deal with radon in Utah?

Here in Utah, the Utah Department of Health’s estimate is that radon is responsible for about 90 deaths per year. So, to answer reader Rich’s question, how much you worry about radon might be influenced by how you feel about that number — is it a lot, or not very much to you?

On one hand, it’s more than the average number of homicides in Utah, about 83 per year. We spend a lot of time worried about murders. On the other, it’s under the number of car deaths we have per year in Utah — we’re at 103 so far in 2023 with much of the year to go. We sometimes don’t spend a ton of time worried about car deaths.

But how concerned you should be about radon doesn’t have to be determined by philosophically debating death statistics. We have better tools than that.

For one, we have the results of a large sample of radon tests in Utah tracked by the Utah Department of Health, almost 17,000 of them taken between the years of 2017 and 2021. The median Utah home returned a level of 2.6 pCi/L in this period, or just under 100 Bq/m³. That’s much higher than the U.S. average of 46 Bq/m³.

How much radiation is 100 Bq/m³? Well, that level of radiation translates to just about 5 millisieverts (mSv) per year — a unit which means nothing to you, I realize. A chest X-ray is about 0.1 mSv; a mammogram is about 0.4 mSv. A whole-body CT scan, on the other hand, would be about 10 mSv of radiation delivered to you.

But the amount of radon in each home varies widely.

Here’s an interactive map that shows you the median reading in each area. Hover over your ZIP code for the median test result, as well as the maximum test result found over the 2017-2021 period. Gray ZIP codes had insufficient data.

In general, homes in the middle of the valley tended to have slightly lower median radon readings than houses in higher-elevation ZIP codes. But a quick examination of the maximums in each ZIP code shows that high readings can be found nearly anywhere.

Ideally, we would have even better data than this. Because the level of radon in an area is largely soil-dependent, we should be able to draw higher-quality maps of where soils tend to be richer in uranium vs. otherwise. If reader Rich’s neighbors are finding high radon readings, he’d be more likely to have radon problems too.

But our last statewide map of these risks came all the way back in 1993 (see page 15). The Utah Department of Natural Resources’ Geologic Hazards Program is working on updating these maps with newer, more accurate readings, but say it’s a very slow process with their team focused on other hazards, like landslides. They say they’re submitting a funding request to the Governor’s office for next year’s budget to hire two more mappers.

One other note: Utah currently has no standards for public buildings to be tested for radon. It’d be especially a good idea in schools and prisons, where people spend a lot of time. As of 2022, only four school districts in Utah (Canyons, Tooele, Davis and Beaver) did sufficient regular testing.

What should I do about it?

Honestly, you can read the tea leaves above, and have a general-ish idea of your relative risk factor in your home — or you can just get your home tested.

Thanks to a grant from the federal Environmental Protection Agency, Utah residents get discounts on radon tests. There are two types of tests: short-term and long-term. Short-term ones take about three days, long-term tests can be taken for 3 months up to a year. The short-term test is $11, the long-term test is $29. Shipping is free!

The vast majority of tests done in the U.S. are short-term tests. I’m going to recommend you do either multiple short-term tests or a long-term one.

I do actually feel guilty about giving the advice to shell out extra bucks, but here’s why I’m giving it: Radon rates in a home fluctuate quite a lot, it appears, depending on the season. Take a look at test results from one Minnesota house, for example:

The tests varied widely — some reading lower than 2.0 pCi/L, others reading above 12 pCi/L.

Every study I looked at found that short term tests were, at best, slightly acceptable proxy measurements for year-round radon levels. At worst, they were nearly meaningless. In Canada, a study of hundreds of paired tests found that a short-term test was hardly correlated at all with long-term tests done six months later. In Iowa, an analysis of 156 short-term tests found they were only 44% correlated with year-round radon averages. A national U.S. study was more optimistic, finding the short-term results were 67% predictive. Even that result gives you a decent chance for a dud.

For the house referenced above, those readings were higher in the summer and lower in the winter. That’s a fairly common result — in the Canada study, 37% of buildings showed greater winter than summer radon, 25.1% showed greater summer radon and 38% of buildings showed relatively minimal change. So I’d recommend doing either multiple short-term tests across multiple seasons, or one long-term test that spans across seasons.

After you estimate your radon level, you’ll want to compare it to your comfort level on increased lung cancer risk — remember, each additional 100 Bq/m³ means about a 20% chance greater risk of getting lung cancer. For what it’s worth, the WHO recommends you mitigate your radon problem if your home has over 100 Bq/m³ (or 2.7 pCi/L), while the EPA recommends taking action at 4.0 pCi/L (or 148 Bq/m³). About 48% of Utah homes are dangerous by that first standard, while about 33% are by the second. Of course, really high radon levels is where you have to worry most.

Taking action means having a radon mitigation system installed in your home. Basically, mitigation companies will likely install a pipe and fan in your foundation to blow the radon out; such a system costs about $1,500 to $2,000 in Utah. In new construction, the installation is much cheaper, about $500.

So to answer your question, reader Rich: to me, radon is a hazard worth finding out about. It’s not likely to kill you, by any means, but given that it’s the talk of your neighborhood, I’d get it checked out.

Andy Larsen is a data columnist for The Salt Lake Tribune. You can reach him at alarsen@sltrib.com.

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