Portland, Oregon Radon Map – Plus Free Tests (for some).

Updated 08/2024.
A perennial Oregon topic is how the influx of migrants from California is affecting life here. But it’s Montana and Idaho we should be worried about. And the migrants I’m referring to aren’t people; they are rocks.
“In the Portland metropolitan area, a lot of the rocks and soil underneath the Willamette Valley were carried down from parts of Idaho and Montana,” said an Oregon Health Authority official quoted by OPB. These long-ago geological travelers carry radon, a dangerous and often deadly gas.
The good news is that you can reduce your risk of exposure with a radon map. You can also do a test at home, and free test kits may be available in your area. If you find you are at risk, you can take specific measures to protect your home from radon. This article covers all the radon updates in terms of the map, tests, and home fixes.
What is Radon?
Radon is a radioactive gas created when uranium decays in the ground. You may think of uranium with nuclear reactions, but in this case, we’re not talking about a man-made issue. Uranium is a natural element found in rocks, soil, and water. Our area has a lot of it, but so do many other areas of the US. One out of every 15 homes in the US has elevated levels of radon.
Uranium decays in the ground, turning into a colorless, odorless, and tasteless gas. As the gas enters the air, it decays and creates radioactive particles. When released outdoors, radon quickly dilutes low concentrations. It is not typically a health concern, but when it enters buildings, it can accumulate to dangerous levels that lead to cancer and other health issues.
How Dangerous is Radon?
The EPA estimates that radon exposure results in 21,000 lung cancer deaths each year in the US and is the second-leading cause of lung cancer nationwide, and the risk isn’t limited to smokers. It is the leading cause of lung cancer among individuals who never smoked.
According to the EPA, the average indoor radon level is about 1.3 pCi/L, and the average outdoor level is 0.4 pCi/L. Radon levels of 4 pCi/L create the same level of risk of dying from lung cancer as dying in a car accident — and that’s for non-smokers. If you smoke, the lung cancer risk at this level of radon exposure goes up to 5x the risk of a fatal car accident. Exposure to higher levels of radon creates even more certainty that cancer will result. The US Surgeon General and EPA recommend fixing homes with radon levels at or above 4 pCi/L.
Why Radon Exposure is More Concerning Today
As real estate agents, we do a lot of education about the risks of radon and the importance of testing, and beginning in 2020, it has become more important than ever. Though more people returned to the office after the 2020 pandemic, stats show that the trend is still higher than prior to COVID. As of 2022, the most recent US Census data, 23.3% of people work from home. This rate is higher than the 2019 estimate of 8%. Portland’s work-from-home average is also much higher than the national average of 15.2%, making radon especially relevant here.
People are spending more time in their homes, potentially increasing their radon exposure, and new public health data has uncovered even more risk areas in Oregon.
More research on short-term tests also shows that single radon tests are not nearly as effective as long-term tests. This means that the radon test you received when you bought your home is good, but to be completely safe, you might want to do more (more on that in the last section of this article).
Where is Radon Exposure an Issue in Oregon?
According to the Oregon Health Authority’s Radon Risk Map, large areas of Portland, including all of Northeast Portland, are at a high risk for radon exposure. In total, 11 Portland zip codes are in the red zone for radon.

Click the radon map to access.
How Are Radon Risk Levels Determined?
Looking at Portland, we see a lot of red (high risk), more yellow (moderate), and some green (low risk), but how do they know? Scientists didn’t have to dig any holes to find where the radon-containing rocks are hiding because radon migrates upwards — into homes and buildings and directly through foundations and walls. So, risk levels are assigned to areas based on tests that check for these invisible, radioactive particles.
For each zip code in the state where an adequate number of test results are available, the Oregon Health Authority makes an assessment based on the following four factors:
● The number of single-family homes with a test result
● the maximum test result value in the zip code area (Radon levels can vary widely from address to address, which is why all homes need to get their own test done and retest every 2 years)
● the average test result value for the area
● the percent of locations within the area that had a test result of more than 4 piC/L (Picocuries per Liter. A “curie” is a unit used to measure radioactivity, named after Marie Curie, the scientist who discovered radium)
How Accurate is the Portland Radon Map?
Fortunately, public awareness about the health hazards of radon is growing, and more homeowners are performing tests and applying mitigation strategies. 2020 was a breakthrough year, showing more results than ever before. Over time, the Oregon Health Authority continues to gather more data from home test kits for radon. However, this could skew the risk level assessment — a large number of homes that mitigate radon will show up as “low” radon homes.
Overall, we don’t recommend that Portland homeowners rely on the radon map alone to assess their radon risk. For one, it’s not a great map. (Sorry OHA!) It’s meant to provide an overview of radon risk statewide and doesn’t get more accurate as you zoom in.
You can get a breakdown of the risk levels of individual zip codes, whether in Portland or elsewhere in Oregon, by going to the OHA’s test results summary table. Simply look up your zip code and find out whether it’s red, yellow or green.
Check the Radon Map, then Test (Even for “Green” Zones)
The reason for fluctuating radon readings in any given area is that radon levels can be affected by a number of things, like radioactive rocks, wind, ground pressure, shifting soil, cold weather, local construction, and earthquakes. Being aware of radon levels in and near your home is important, as radon is responsible for about 21,000 lung cancer deaths each year from radon exposure, according to the Environmental Protection Agency (EPA), with about 2,900 of those deaths occurring in people who have never smoked.
Because radioactive rocks can be anywhere, every home should have a radon test performed, even if the home’s zip code is “green”. However, radon testing is not currently required under Oregon law as part of the home sale inspection. That means it’s up to buyers to request the test as part of the home inspection.
Here are some important things to know before you test:
■ Radon levels fluctuate over time, even by season. It’s best to test in winter when test scores are highest.
■ New research shows that the most accurate radon tests are long-term: 90 days or more. They account for daily fluctuations and provide a more precise average. A best practice for home buyers is to get a 48-hour test done as part of the home inspection, then retest using a longer-term test the following winter before undertaking mitigation (or considering yourself safe!)
■ Repeat the radon test every two years. The definition of a radioactive material is that it is unstable — radon-containing rocks may fluctuate in the amount of radon they release.
■ New homes built in Portland (in fact a wider area: all of Baker, Clackamas, Hood River, Multnomah, Polk, Washington and Yamhill counties) since 2013 are required to use Radon Resistant New Construction (RRNC). However, OHA still recommends that new homes be tested for radon.
Visit the Oregon Health Authority website for more information about testing your Portland home for radon, health risks, and mitigation.
How to Obtain Free Radon Testing Kit
Some Oregon zip codes don’t have enough test results to assign a risk level; if you live in one of these zip codes, OHA will send you a free test kit so that the data will be included in future radon maps.
How to Reduce Radon Levels In Your Home
Hire a State-certified, radon-qualified contractor—The Oregon Health Authority (OHA) has a list of Oregon companies that have at least one radon specialist on staff. You can also search the National Radon Proficiency Program’s directory or do a search on the National Radon Safety Board’s website.
Install a radon mitigation system—The EPA claims that some radon mitigation systems can reduce the radon in a home up to 99% and that most homes can be fixed for about the same cost as other common household repairs.
Certain fixes can reduce radon levels inside your home, but according to Consumer Reports, most homeowners with high radon levels don’t get it down below 2 pCi/L. At this level, there’s still a slightly elevated risk for lung cancer.
The gas can enter homes through cracks, gaps, windows, drains, and areas around pipes and cables. Here are some ways to reduce your exposure.
Seal cracks: Use caulk, plaster, or other materials along walls, floors, and foundation openings. You can also seal gaps around pipes and cables with expanding foam.
Improve ventilation: Since radon becomes dangerous due to the gas accumulation over time, help ensure it vents out of the home. Install more wall or window vents and make sure all existing vents remain unblocked. A fan sump is also highly effective at drawing radon from the ground into a pipe that leads outside. You should only add ventilation at ground level because upper vents will only draw in gas into the home like a chimney.
Create barriers: Put polyethylene sheets or a vapor retarder on gravel.
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