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
What is it about radon that makes it harmful?
When radon and its decay products are inhaled
into your lungs they emit 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
to radon-related cancer. Most of the alpha particle radiation comes
from radon decay products. However, since it is easier to measure
radon rather than its decay products, people usually characterize
the exposure by the amount of radon in their living spaces.
What elements of the environment contain
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.
How does radon move around?
Radon can move by diffusion in response to
a concentration difference or by advection in response to a pressure
difference. Radon leaves the ground generally by diffusion. Radon
travels into houses generally by a combination of diffusion and advection.
In most soils radon doesn't travel more than a few feet before decaying.
What is the most accurate way to measure radon
Continuous electronic radon monitors generally
produce the most accurate radon measurements. However, they are expensive
and can be difficult to operate. Yearlong 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.
Is it a good idea to do both short and long-term
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 yearlong 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.
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¯’". Another unit commonly used for radioactive concentrations
is the SI unit Becquerels per meter cubed (Bq/m"). A Becquerel is
one radioactive disintegration per second.
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).
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.
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 never smoker
- an ex-smoker
- a smoker
then your lifetime risk of getting lung cancer
that is related to your radon exposure is about
- 1 chance in 250
- 1 chance in 100
- 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.
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.
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 RCP-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
Does the age of my house affect the radon
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.
Why are radon levels in my home "high" while
those in my neighbor's home 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
Are there areas where radon is likely to be
Yes! We've found that the average radon can
vary dramatically from town to town. See the Radon Maps page.
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.
Is radon-related to 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
How Does Radon Enter A Home?
Radon can seep into a home through dirt floors,
cracks and pores in concrete walls and floors, hollow-block walls,
joints, drains pipes, and sump pumps. Building supplies made from
materials containing uranium are rarely a significant source of residential