in well water can contribute to the indoor air levels
of radon in your home. Radon is released into the air
as the water pours into sinks, tubs and appliances.
Household activities that use hot water, such as showering
and washing dishes or clothes, can release large amounts
of radon particularly in the rooms where this water
is used. Scientists are now looking at the possibility
that the drinking of water with high amounts of radon
may cause other types of cancers.
The concentration of radon
in water is usually given in picocuries per liter (pCi/L)
as in air measurement of radon. While the average concentration
of radon in U.S. groundwater is below 1,000 pCi/L,
some levels of groundwater have been found above 1,000,000
pCi/L. The highest amounts have been found in the Northeast.
Private wells tested in Connecticut indicate an average
radon level of about 3,000 pCi/L. There are reduction
systems available which are very effective in reducing
any elevated level of radon in water.
The State of Connecticut Department of Health Services
Radon Program recommends that you test your water for
radon if your water comes from a private well. Be sure
to use a laboratory that follows an EPA approved testing
method. Since radon levels may change over time, it
is useful to obtain a second test (if time permits)
during another season. The results can be averaged
together to assess your risk from radon in water.
Your Water Test Results
The U.S. Environmental Protection Agency (EPA) has
proposed a standard of 300 pCi/L of radon in public
drinking water. As discussed earlier, the average radon
concentration in private wells in Connecticut is 3,000
pCi/L or ten times the proposed standard. Therefore,
it is likely that your private well water has radon
levels in excess of the proposed public water standard.
While public drinking water supplies are the responsibility
of the utility companies, a private well is the responsibility
of the homeowner. The following section will help you
decide if you need to take action to lower the radon
level in your water.
a Decision About Radon in Water
Since water radon treatment systems are expensive (ranging
from $800 to $4,000), the decision to treat your water
should be made carefully. The following questions should
be answered to help you decide if your water should
be treated for radon.
1. Will the radon
released into the air from your everday water use equal
or exceed the current EPI indoor air guideline of 4
pCi/L or is your radon in water level 40,000 pCi/L
To answer these questions, you must first know the
amount of radon that is transferred from the household
water to the household air. Of primary concern is the
radon in household air, since breathing this radon
will place you at risk for lung cancer. You can find
out the amount of radon released into the air from
the water by using the following rule:
Every 10,000 pCi/L of radon in water contributes
about 1 pCi/L of radon to the radon level that already
exists in the household air. (This estimate can vary,
depending on your water use.) Therefore, if your radon
in water level is 40,000 pCi/L or higher, you should
treat the water since the radon from the water alone
will equal or exceed the 4 pCi/L guideline.
2. Is your radon in
water level between 5,000 and 40,000 pCi/L?
At these levels there is still a significant risk of
lung cancer from breathing radon and a lesser risk
of stomach cancer from ingesting it. Your water should
be treated. However, if the amount of money that you
have budgeted for radon reduction is limited, it is
more important that you ensure that air levels are
below 4 pCi/L by controlling soil gas entry routes.
3. Is your radon level
between 1,000 and 5,000 pCi/L?
There is a risk for development of lung cancer from
exposure to radon at any level. However, the indoor
air concentrations resulting from these radon in water
levels may be similar to your outdoor or background
levels. Therefore, treating water at this level may
not be worth the expense.
4. Is your radon in
water level between 300 and 1,000 pCi/L?
Reduction of radon below these levels may not always
be possible or practical in private wells. Evidence
at this time suggests that radon in water at these
levels represents the lowest range of health risk and
further action is not recommended because of current
costs of reducing radon in water.
Radon In Water
Removing radon from the well water before it enters
the house is the most effective treatment. Radon levels
in the water can be reduced either by the use of a
granulated activated carbon (GAC) filter unit or by
the use of an aeration treatment system. The type of
reduction method depends upon the radon level and how
much water is used.
The GAC system has
special charcoal filters which remove the radon from
the water. Typical GAC systems cost between $800 and
$1,500. GAC units will build up radioactive decay particles
with use. The amounts of radiation accumulated by a
GAC depends on the amount of radon in the well water
and the amount of well water used. Your GAC filter
should be changed periodically according to the recommendations
of the manufacturer. Not doing so will result in the
filter itself becoming an additional source of radiation
requiring special disposal, and could result in bacterial
contamination as well. Use of GACs for treatment of
radon is normally limited to wells with radon levels
from 5,000 to 10,000 pCi/L.
The aeration system
forces the radon gas from the water by using air bubbles
or other methods and vents it outside the home. Typical
aeration systems cost between $2,500 and $4,000. The
removal of radon from the water by the aeration unit
may result in very high levels of radon in the
air. Therefore, it is extremely important that the
aeration unit's radon-laden air be vented away from
the home, where it will not leak back into the house.
The vent pipe for the aeration unit should be placed
above the roofline.
Wells with very high levels
of radon may also contain high levels of radium and
uranium. Separate tests are required to identify these
elements. An additional activated charcoal or resin
bed filter may be needed to treat these contaminants.
The filters should be maintained according to the manufacturers
There are maintenance and
installation concerns with either type of radon treatment
unit. Be certain that all appropriate permits are obtained
and state and local building code requirements are
met during installation of these units.