Radon Levels
Radon level of 3 pCi/L: is it bad?
Short answer
A radon level of 3 pCi/L is below the 4 pCi/L action level but inside the 2 to 4 range where EPA recommends considering a fix, and it is above WHO's recommended reference level of 2.7 pCi/L. It is more than twice the U.S. indoor average, and no level of radon is safe.
Next step: pick the right test for your home. Which test to use
Key takeaways
- 3 pCi/L is 75 percent of EPA's 4 pCi/L action level.
- In EPA's 2 to 4 pCi/L range: consider fixing.
- EPA estimates the average U.S. home at about 1.3 pCi/L; 3 pCi/L is 2.31 times that.
- Confirm a short-term result with a second test; a long-term test shows the year-round average best.
Where it sits
Is a radon level of 3 pCi/L high?
- About 110 Bq/m3
- 3 pCi/L in becquerels per cubic meter, at about 37 Bq/m3 per pCi/L (calculated).
- 75 percent
- Of EPA's 4 pCi/L action level (calculated).
- 2.31 times
- The U.S. indoor average of about 1.3 pCi/L (calculated).
On the risk chart, 3 falls between the 2 pCi/L row (about 32 per 1,000 people who smoked, about 4 per 1,000 who never smoked) and the 4 pCi/L row (about 62 and about 7). Readings such as 3.1 or 3.6 sit in the same place.
The range matters because there is significant risk below 4 pCi/L and no known safe level, which is why EPA has long recommended considering a fix between 2 and 4 pCi/L.
Where 3 pCi/L sits against EPA's and WHO's reference points
Against outdoor air (about 0.4 pCi/L)
7.5 times the outdoor average (calculated)Against WHO's recommended reference level (100 Bq/m3, 2.7 pCi/L)
Above itEPA's band
In EPA's 2 to 4 pCi/L range: consider fixing
What to do
What to do about a radon level of 3 pCi/L
EPA recommends fixing a home when the radon level is 4 pCi/L or higher. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. For a reading of 3 pCi/L, the steps come to this:
Steps for a reading of 3 pCi/L
Confirm the number
A long-term test (more than 90 days) gives a better picture of the year-round level than one short-term result of 3 pCi/L.Weigh a fix
EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Many homes can be brought to 2 pCi/L or less.Get an estimate if you decide to fix
From a qualified contractor credentialed by your state or a national proficiency program.Retest
After any fix, and after renovations or a move to a lower floor.
The full sequence of tests, from a first result to the decision to fix, is drawn on radon testing.
Health risk
The lung cancer risk at 3 pCi/L
EPA's risk chart has no row for 3 pCi/L, so the table shows the rows either side of it. The chart estimates how many people out of 1,000 could get lung cancer if exposed to a level over a lifetime, for people who smoked and people who never smoked.
3 pCi/L sits between the 2 and 4 pCi/L rows, halfway between them (our calculation). At 4 pCi/L the chart gives about 62 in 1,000 people who smoked (5 times the risk of dying in a car crash), and about 7 in 1,000 who never smoked (the risk of dying in a car crash); at 2 pCi/L, about 32 in 1,000 people who smoked (6 times the risk of dying from poison), and about 4 in 1,000 who never smoked (the risk of dying from poison).
| Radon level | People who smoked | People who never smoked | What to do |
|---|---|---|---|
| 4 pCi/L (150 Bq/m3) | About 62 in 1,000 | About 7 in 1,000 | Fix your home |
| 2 pCi/L (75 Bq/m3) | About 32 in 1,000 | About 4 in 1,000 | Consider fixing between 2 and 4 pCi/L |
These are population estimates from EPA's 2003 assessment of radon risk in homes, not a forecast for any one person. Your own chances depend mostly on how much radon is in your home, how much time you spend there, and whether you smoke or have ever smoked; a former smoker's risk may sit between the two columns. Lung cancer risk is estimated to rise by about 16% per 100 of long-term average radon.
EPA's whole chart, from outdoor air to 20 pCi/L, is drawn on radon levels.
How sure
How certain is a reading of 3 pCi/L?
One test is a sample of a level that moves. Radon levels tend to vary from day to day and season to season, so a is less likely than a to show the year-round average, and levels can change from hour to hour. A single short-term result of 3 pCi/L is a reading for those days.
Where the test sat matters as much. A test belongs in the lowest lived-in level, and levels are usually higher in basements and rooms in contact with the ground. Testing is the only way to know the radon level in a specific building. Placement and are on radon testing.
With a system
How much a radon system would lower 3 pCi/L
Each technique has a typical reduction range, and with today's technology radon levels in most homes can be reduced to 2 pCi/L or below. Applied to 3 pCi/L, the low end of each range gives the figures below: our arithmetic on the published ranges, not a prediction for your house. Only a test after installation shows what a system achieved.
| Technique | Typical reduction | From 3 pCi/L, about |
|---|---|---|
| Active sub-slab suction (the usual system) | 50 to 99 percent | 1.5 pCi/L or lower |
| Sump-hole suction | 50 to 99 percent | 1.5 pCi/L or lower |
| Drain-tile suction | 50 to 99 percent | 1.5 pCi/L or lower |
| Submembrane suction (crawl spaces) | 50 to 99 percent | 1.5 pCi/L or lower |
| Passive sub-slab suction (no fan) | 30 to 70 percent | 2.1 to 0.9 pCi/L |
Which technique fits depends on the foundation; see radon mitigation systems, and for cost, radon mitigation cost.
Situations
Where people meet a reading of 3 pCi/L
3 pCi/L in three common situations
3 pCi/L after a mitigation system
As a post-mitigation result, between 2.0 and 4.0 pCi/L means consider fixing the building, and with a system already installed, more work may be needed to lower the radon further.3 pCi/L in a home you are buying
Even radon levels below 4 pCi/L pose some risk. Check that the test covered the lowest level you will use, since a buyer may live in a lower area of the home than the seller did.3 pCi/L against WHO's figure
3 pCi/L is above WHO's recommended reference level of 2.7 pCi/L (100 Bq/m3). EPA has long recommended considering a fix between 2 and 4 pCi/L, because there is significant risk below 4 and no known safe level.
Retest
When to retest after 3 pCi/L
3 pCi/L is 1 pCi/L under the (our calculation), close enough to 4 that a short-term test is less definitive about which side of the line the year-round level falls. A long-term test, through winter if you can, when the heating runs day and night, is the follow-up that settles it.
| When | What to do |
|---|---|
| Sometime in the future | You may want to test again even below 4 pCi/L |
| After a renovation | Major renovations can change the radon level in any home |
| Before using a lower floor | Retest on that level |
| Without a mitigation system | Every 5 years, the Minnesota health department's advice |
| When selling | A buyer may ask for a new test if yours is more than about two years old |
The general answer is on how often should I test for radon.
Questions
Radon level of 3 pCi/L: questions
Is 3 pCi/L of radon safe?
No level is called safe; any radon exposure carries some risk. 3 pCi/L is below the 4 pCi/L action level, but in the 2 to 4 range where EPA recommends considering a fix.
Do I need radon mitigation at 3 pCi/L?
EPA recommends considering it. The decision is yours: weigh a confirmed result, how you use the lowest floor, and the cost.
What is 3 pCi/L in Bq/m3?
It is about 110 Bq/m3, at about 37 Bq/m3 per pCi/L (our calculation).
Should I buy a house with a radon level of 3 pCi/L?
EPA's guidance for a home under 4 pCi/L is the same whoever owns it: consider a fix from 2 pCi/L. Check that the test was in the lowest level you will use; a buyer may live in a lower area than the seller tested.
Is 3 pCi/L in a basement different from upstairs?
Usually the basement reads higher. Levels are usually highest in basements and rooms in contact with the ground, though considerable levels can occur above the ground floor too. A test belongs in the lowest lived-in level.
How long should I wait to retest after 3 pCi/L?
There is no fixed interval below 4 pCi/L; you may want to test again sometime in the future, and after renovations or a move to a lower floor.
Can 3 pCi/L be brought down?
Usually. Radon levels in many homes can be reduced to 2 pCi/L or less, and with today's technology most homes can reach 2 pCi/L or below.