General ( Glossary ) Health risks Testing Mitigating Regional
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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.
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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.
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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.
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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.
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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.
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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)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)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.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).
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.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, SARADTOP
Questions/Comments, e-mail: Dr. Steck
Last revised : 15 July, 2004
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since
07/15/04
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