Radon Levels
Radon level of 5 pCi/L: is it bad?
Short answer
Yes: a radon level of 5 pCi/L is above the 4 pCi/L action level, and once a follow-up test confirms it, EPA recommends fixing the home. There is no separate tier for 5 pCi/L; the guidance is the same as for any confirmed result at or above 4.
Next step: pick the right test for your home. Which test to use
Key takeaways
- 5 pCi/L is 1.25 times EPA's 4 pCi/L action level.
- At or above EPA's action level: fix once confirmed.
- EPA estimates the average U.S. home at about 1.3 pCi/L; 5 pCi/L is 3.85 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 5 pCi/L high?
- About 185 Bq/m3
- 5 pCi/L in becquerels per cubic meter, at about 37 Bq/m3 per pCi/L (calculated).
- 1.25 times
- EPA's 4 pCi/L action level (calculated).
- 3.85 times
- The U.S. indoor average of about 1.3 pCi/L (calculated).
On the risk chart, 5 falls between the 4 pCi/L row (about 62 lung cancers per 1,000 people who smoked, about 7 per 1,000 who never smoked) and the 8 pCi/L row (about 120 and about 15). Readings such as 5.1 or 5.3 sit in the same place.
If 5 pCi/L was a first short-term result, take a follow-up test to be sure, either long-term or a second . If it came from a , fix the home. Readings between 4 and 5, such as 4.1 or 4.8, are covered in is a radon level of 4.1 considered high.
Where 5 pCi/L sits against EPA's and WHO's reference points
Against outdoor air (about 0.4 pCi/L)
12.5 times the outdoor average (calculated)Against WHO's recommended reference level (100 Bq/m3, 2.7 pCi/L)
Above itEPA's band
At or above EPA's action level: fix once confirmed
What to do
What to do about a radon level of 5 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 5 pCi/L, the steps come to this:
Steps for a reading of 5 pCi/L
Confirm it
If 5 pCi/L was a first short-term result, take a follow-up test: a long-term test for the year-round average, or a second short-term test if you need results quickly.Decide on the confirmed number
EPA recommends fixing a home when the radon level is 4 pCi/L or higher. The decision rests on one long-term test or the average of two short-term tests.Hire a qualified contractor
Get more than one estimate and a written contract; see radon mitigation.Test after the fix
No sooner than 24 hours and within 30 days after the system starts, then at least every two years.
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 5 pCi/L
EPA's risk chart has no row for 5 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.
5 pCi/L sits between the 4 and 8 pCi/L rows, a quarter of the way from the lower row (our calculation). At 8 pCi/L the chart gives about 120 in 1,000 people who smoked (30 times the risk of dying in a fall), and about 15 in 1,000 who never smoked (4 times the risk of dying in a fall); at 4 pCi/L, 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).
| Radon level | People who smoked | People who never smoked | What to do |
|---|---|---|---|
| 8 pCi/L (300 Bq/m3) | About 120 in 1,000 | About 15 in 1,000 | Fix your home |
| 4 pCi/L (150 Bq/m3) | About 62 in 1,000 | About 7 in 1,000 | Fix your home |
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 5 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 short-term test is less likely than a long-term test to show the year-round average, and levels can change from hour to hour. A single short-term result of 5 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 5 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 5 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 5 pCi/L, about |
|---|---|---|
| Active sub-slab suction (the usual system) | 50 to 99 percent | 2.5 pCi/L or lower |
| Sump-hole suction | 50 to 99 percent | 2.5 pCi/L or lower |
| Drain-tile suction | 50 to 99 percent | 2.5 pCi/L or lower |
| Submembrane suction (crawl spaces) | 50 to 99 percent | 2.5 pCi/L or lower |
| Passive sub-slab suction (no fan) | 30 to 70 percent | 3.5 to 1.5 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 5 pCi/L
5 pCi/L in three common situations
5 pCi/L on a first short-term test
Confirm it before deciding, with a long-term test or a second short-term test. The decision rests on the long-term result, or on the average of the two short-term results.5 pCi/L in a basement you have started using
When you begin occupying a lower level such as a basement, retest on that level. Levels are usually higher in rooms in contact with the ground.5 pCi/L after a renovation
Major renovations can change the radon level in any home, so test again once the work is done, in the lowest lived-in area.
Retest
When to retest after 5 pCi/L
5 pCi/L is 1 pCi/L over the (our calculation): over the line, but close enough that a single short-term test is less definitive. Either follow-up works. A long-term test gives the year-round answer; a second short-term test gives the quicker one.
| When | What to do |
|---|---|
| To confirm the first result | With a long-term test, or a second short-term test if you need results quickly |
| After a system is installed | No sooner than 24 hours and within 30 days, with a two- to seven-day test |
| With a system in place | At least every two years |
| After a remodel | In the lowest lived-in area |
The general answer is on how often should I test for radon.
Questions
Radon level of 5 pCi/L: questions
Is 5 pCi/L of radon safe?
No. 5 pCi/L is at or above EPA's 4 pCi/L action level, where EPA recommends fixing the home once the result is confirmed.
Do I need radon mitigation at 5 pCi/L?
Yes, by EPA's guidance, once a long-term test or the average of two short-term tests confirms the level is 4 pCi/L or more.
What is 5 pCi/L in Bq/m3?
It is about 185 Bq/m3, at about 37 Bq/m3 per pCi/L (our calculation).
Should I buy a house with a radon level of 5 pCi/L?
A high level is fixable. Buyers and sellers should discuss the timing and costs of radon reduction, and the contract can say when mitigation happens and who pays. See should I buy a house with radon.
Is 5 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 5 pCi/L?
Follow up soon, with a long-term test if you have time or a second short-term test if you need results quickly.
Can a system bring 5 pCi/L under 2?
Often. With today's technology radon levels in most homes can be reduced to 2 pCi/L or below. From 5 pCi/L that is a cut of 60 percent (our calculation), inside the 50 to 99 percent typical of active soil suction.