Frequently Asked Questions About Radon

      General ( Glossary )                  Health risks                  Testing                         Mitigating                         Regional

What is radon? Are radon levels something I really need to be concerned with? What is the most accurate way to measure radon levels? Can anything be done to reduce the hazard associated with radon? Are there areas where radon is likely to be high?
Where does radon come from? What is it about radon that makes it harmful? Does the Minnesota Radon Project meet EPA standards? Who can mitigate my radon problem? Is high indoor radon unique to Minnesota?
What does pCi/L mean? Is radon-related lung cancer fatal? Why is my home "high" while  my neighbor's home is "low?"    
What levels of radon are acceptable? Are there any other health effects with radon? Where can I get electronic radon monitors?    
Does the age of my house affect the radon level?        
Are radon levels affected by the ventilation in my house?        
How does radon move around?        

e-mail me with suggestions for more FAQ answers

1. What is radon?  
Radon is a radioactive gas that comes from the decay of radium in the soil. Radium is a decay product of uranium. Uranium is present in almost all rocks and soil and material derived from rocks (more). Radon is a colorless, odorless, invisible gas that occurs naturally. Chronic exposure to elevated radon levels has been linked to an increased incidence of lung cancer in humans. bd14565_.gif (183 bytes) TOP

2. Are radon levels something I really need to be concerned with?
Yes. For most people, radon is their largest source of exposure to nuclear radiation. The US Environmental Protection Agency (EPA) has identified radon as the second leading cause of lung cancer in the United States. Many homes, particularly homes in the upper Midwest, contain radon concentrations that are high enough to give their occupants lifetime exposures of the same size as those received by underground miners who showed the increased risk of lung cancer mortality. see FAQ 19. bd14565_.gif (183 bytes)TOP

3. What is it about radon that makes it harmful?
When radon and its decay products are inhaled into your lungs they emit energetic particles called alpha particles. These alpha particles can strike the sensitive lining of the bronchi. When this happens, the cells in your lungs are damaged, subsequently increasing your risk of developing a cancer. Most of the alpha particle radiation comes from radon decay products. People usually characterize their exposure to this radiation damage by the amount of radon in their living spaces since it is easier to measure radon rather than energy that radon decay products deposit in the lung tissues. bd14565_.gif (183 bytes)TOP

4. Where does radon come from?
Radon is constantly being generated by the radium in rocks, soil, water and materials derived from rocks and soils. Radium is present at about 0.5 to 5 parts per million (PPM) in common rocks and soils. The radon generated in rocks or water usually stays trapped in that material unless the rocks are highly fractured or the water is mixed with the air. Radon generated in soil has about a 40% chance of escaping into the soil gas. bd14565_.gif (183 bytes)TOP

5. How does radon move around?
In most soils radon travels only a few feet before decaying. Thus, the radon that gets into your home comes from the soil immediately around and underneath your house. In water, rocks, or other dense materials radon doesn't even travel a few inches.  Radon can move by diffusion  ( concentration differences) or by advection (pressure driven).   Radon travels into houses generally by a combination of diffusion and advection. Radon escapes from the ground into the atmosphere by diffusion.  bd14565_.gif (183 bytes)TOP

6. What is the most accurate way to measure radon levels?
Continuous electronic radon monitors generally produce the most accurate radon measurements. However, they are expensive and can be difficult to operate. Year-long measurements by alpha-track (ATD) detectors in your living spaces provide adequate measurements for decision-making. In most homes, radon varies dramatically from day-to-day, week-to-week, season-to-season, and to a lesser extent year-to-year. This means that if you want to assess your long-term exposure to radon, you need to measure over a period of a year or more. In addition, in my opinion, you only need to know your average radon exposure to an accuracy of about 25% in order to make a decision about what steps you might take to reduce your radon exposure. ATDs can readily supply that information at a reasonable cost. (see Radon Testing)bd14565_.gif (183 bytes)TOP

7. Is it a good idea to do both short and long-term tests?
Possibly. If you have reason to suspect that you might have extremely high radon or if you just can't wait a year for the results, then take a short-term test and start a long-term test alongside. Radon fluctuates daily and seasonally. For this reason, radon measurements should be taken for at least a month for a short-term test. Short-term test results will usual be within a factor of 3 of the long-term average. So if you get a short-term result of 3 pCi/L, you can expect you long-term radon to be within the range from 1 to 9 pCi/L. A year-long test in a living space where you spend a lot of time would be the most efficient and effective way for the first assessment of the radon hazard in your home. (see Radon Testing)bd14565_.gif (183 bytes)TOP

8. What does pCi/L mean?
Picocuries per liter (pCi/L) is a unit for measuring radioactive concentrations. The curie (Ci) unit is the activity of 1 gram of pure radium 226. Pico is a scientific notation term which means 1�10���. A typical value for radon in the living spaces of a US home is 1 pCi/L. The international unit for radiation concentrations is a  Becquerel per meter cubed (Bq/m�). A Becquerel is one radioactive disintegration per second. One pCi/L is equivalent to 37 Bq/m�. See the Glossary for definitions for units of radon progeny and radiation dose.bd14565_.gif (183 bytes)TOP

9. Are radon levels affected by the ventilation in my house?
Yes. Sometimes radon concentrations can be reduced to acceptable levels by increased ventilation. Most of the time, other methods are needed to reduce radon levels (mitigate) to acceptable levels (see FAQ 12 and 13). bd14565_.gif (183 bytes)TOP

10. What levels of radon are safe?
Unknown. Studies of the effects of radon in homes have produced mixed results. Some studies indicate a positive association, others don't. These are very difficult studies to do well because smoking-related lung cancer is such a large component of the total lung cancer rate and because it is very difficult to reconstruct the lifetime dose from radon decay products for any individual. It is virtually impossible to avoid exposure to radon concentrations below 1 pCi/L because outdoor air is generally contains radon concentrations from 0.1 to 1 pCi/L. bd14565_.gif (183 bytes)TOP

11. What levels of radon are acceptable?
You must provide the answer to this question based on the following data and your personal risk tolerance. If you lead a normal life, live in spaces that average 4 pCi/L of radon, and if you are: (a) a never smoker, (b) an ex-smoker (c) a smoker, then your lifetime risk of getting lung cancer that is related to your radon exposure is about (a) 1 chance in 250; (b) 1 chance in 100; (c) 3 chances in 100. For comparison, substances in the food chain are regulated at levels that produce much lower risks. Usually food or drink is labeled contaminated if they produce a 1 in 100,000 lifetime chance of producing cancer. Most scientists believe that above about 10 pCi/L the risk associated with radon would increase in direct proportion with the radon concentration. Below this value, many believe that the risk decreases in direct proportion but that there could be a safe threshold value. We don't know for sure what that value is or whether it exists. bd14565_.gif (183 bytes)TOP

12. Can anything be done to reduce the hazard associated with radon?
Yes, definitely. Often the solution is simple and inexpensive. However, the best solution depends on the size and nature of the radon risk. For example, suppose you find that your basement bedroom has high radon. A possible simple solution might be to avoid spending long stretches of time in that room by moving your bedroom to a lower radon room upstairs, if that option exists. Other situations may require other mitigation solutions. The "standard" active mitigation system, that usually involves soil depressurization, costs about $500 to $2000 installed. bd14565_.gif (183 bytes)TOP

13. Who can mitigate my radon problem?
You probably can if you're handy. In many areas, contractors (called mitigators) are available too. The EPA and your state health department can provide you with additional information, including instruction manuals and names of CRP-listed mitigators. Whoever does the work, be sure to make periodic long-term measurements to insure that the system continues to reduce your radon to acceptable levels. bd14565_.gif (183 bytes)TOP

14. Does the age of my house affect the radon level?
Possibly. Some houses show an increase of radon with age, other houses show a decrease and still others show no change with age. Unfortunately, we haven't found any single factor like the age of the house, energy efficiency, or basement structure that can accurately predict the radon level in any house. You really have to measure the radon in your house to know for sure. bd14565_.gif (183 bytes)TOP

15. Why are radon levels in my home "high" while those in my neighbors' homes are "low?"
Many things influence the amount of radon in a home. The variation in radon levels from home-to-home comes from the variation in the factors that control radon entry and retention. There are so many factors like the structure of the soil, the way the house is connected to the ground, the way the house is heated and cooled, that it is extremely difficult to predict accurately the radon in neighboring homes. We've found that, in Minnesota neighborhoods, most of the homes are within a factor of 2 of the neighborhood average. So, for example, if three of your neighbors made measurements and they averaged 20 pCi/L, your home is likely to have radon between 10 and 40 pCi/L. It is very likely to exceed the EPA's 4 pCi/L action level. bd14565_.gif (183 bytes)TOP

16. Are there areas where radon is likely to be high?
Yes. We've found that the average radon can vary dramatically from town to town. See the Radon Maps page. bd14565_.gif (183 bytes)TOP

17. Is high indoor radon unique to Minnesota?
No. Some high radon homes have been found in every state and most countries. However, the upper Midwest appears to contain many regions of elevated radon ( see UMATD map). The average US home contains about 1.3 pCi/L while the average Minnesota home has more than 3 pCi/L. bd14565_.gif (183 bytes)TOP

18. Are there any other health effects with radon?
Not that we know for sure. No other cancers or diseases have yet been positively associated with radon exposure. However, radon is absorbed into the body and can irradiate tissues other than the lung. bd14565_.gif (183 bytes)TOP

19. Is radon-related lung cancer fatal?
Most often, yes. Lung cancer is a disease that has a very poor survival rate. Prevention is the most effective defense. Don't smoke and don't breathe elevated concentrations of radon. bd14565_.gif (183 bytes)TOP

20. Does the Minnesota Radon Project meet EPA standards?
We operate in accordance with EPA guidelines and employ accepted, standard scientific practices.  When the EPA had an active Radon Measurement Proficiency Program(RMP), Dr. Steck was an RMP listed individual and the ATDs that we provide met EPA requirements of the US EPA Radon Measurement Proficiency program. We continue to maintain RMP level quality and calibration.bd14565_.gif (183 bytes)TOP

21. Where can I get electronic radon monitors?
First, ask yourself why you would want one. Inexpensive electronic monitors (~$100)are not very accurate and respond slowly (a matter of days) to changes in radon concentrations. So they are not good "radon alarms" or controls for HVAC systems. More accurate and responsive models range in price from ~$1000 to $60,000. Some brand names of continuous monitors(ordered in increasing $ )SafetySiren, Sun Nuclear, femto-Tech, Pylon, Durridge Niton, SARADbd14565_.gif (183 bytes)TOP

 Back to the MRP Homepage

Questions/Comments, e-mail: Dr. Steck

Last revised : 15 July, 2004 

VisitorHit Counter since 07/15/04

The views and opinions expressed on the web sites hosted on this server are strictly those of the author.

The contents of the web sites on this server have not been reviewed or approved by the College of St. Benedict|St. John's University.