In the past, whenever people bought a home, their main concern was the physical house; that is, the structural integrity of the building; the condition of the mechanical equipment such as the heating system, plumbing, water heater; the adequacy of the electrical system; the condition of the roof; whether the basement was dry; and whether there was a termite condition. In recent years, another factor has entered into the decision process-environmental problems. Some of these problems, such as a high radon concentration or deteriorating asbestos insulation, are potential health hazards. Others, like a leaky buried oil tank, can contaminate the soil and eventually the aquifer (water table). In all cases, it costs money to correct the problems. This cost should be added to the overall sale price of the house to determine the true cost of purchasing the house.

In this chapter, I will discuss environmental problems that are or should be of concern to the home buyer or homeowner. There is no doubt that in the future, as technology improves and more statistical health information becomes available, additional items will be added to the list of environmental problems.


Although the health risks associated with exposure to high concentrations of radon have been known for decades because of experience with uranium miners, it wasn’t until December 1984 that it was realized that people in homes can also be exposed to high concentrations of radon resulting from uranium deposits in the soil on which the houses are built. A worker in a nuclear generating plant passed through a radiation detection monitor as he entered the plant. It turned out that his home had twenty times more radiation than is allowed in a uranium mine.

Radon is a gas present in varying quantities in the atmosphere and soils around the world. It is colorless, odorless, and tasteless, and is produced by the natural radioactive decay of uranium deposits in the earth. Prolonged exposure to high concentrations of radon can cause cancer. According to the U.S. Environmental Protection Agency (EPA), scientists estimate that between 5,000 and 20,000 lung-cancer deaths a year in the United States can be attributed to radon.

The concentration of radon in the air is measured in units of picocuries per liter of air (pCi/l). Based on currently available information, the EPA has set guidelines for radon levels in residential structures. (See TABLE 20-1.) Their “action level” is 4 pCi/l; that is, no action is needed if the radon concentration is below 4 pCi/l. The EPA acknowledges that even the action level is not risk free because exposure to an annual radon level of 4 pCi/l is equivalent to the risk of smoking ten cigarettes a day or having two-hundred chest X-rays a year. The action level was set at 4 pCi/l because in some cases reduction below that level might be difficult or impossible to achieve.

Table 20-1.

U.S. EPA guidelines for residential radon.

Annual average

Radon level Recommended action
Over 200 pCi/l Take action to reduce levels
within several weeks.
Between 20 and Take action to reduce levels
200 pCi/l within several months
Between 4 and Exposures in this range are
20 pCi/1 considered above average
You should take action to
reduce levels to about 4 pCi/l
or below within a few years
(sooner if levels are at the
upper end of this range).
Below 4 pCi/l Exposures in this range are
considered average or slightly
above average.
Although exposures in this
range do present some
increased risk of lung cancer,
reductions of levels this low
may be difficult, and
sometimes impossible, to
Below 1.0 pCi/l These are average first-floor
residential levels.

Although radon gas is present in varying quantities in soils around the world, not every house has a problem with high radon levels. It is possible for one house to have a very low radon concentration while an adjacent house has a very high level. It depends on the construction of the house, the uranium-radium content in the soil, and geological formation below the house. The only way to know if a house has a radon problem is to test it. The radon concentration in a house varies with time. It is affected by a number of environmental factors such as rain, snow, barometric pressure, and direction of wind relative to open windows, and by induced negative pressures caused by periodic use of exhaust fans, attic fans, fireplaces, and heating systems. Consequently, the most accurate method of determining the average annual radon concentration is a long-term test. However, since time is usually limited in real estate transactions, a long-term test is not practical, and consequently a charcoal canister with a test period of three to seven days is generally used.

Canisters can be purchased in hardware stores and home centers. Also, in many areas professional home-inspection companies offer radon-testing services. If you intend to place the radon-detection canister yourself, make sure that you follow the directions carefully; otherwise, the results might be inaccurate.

Since radon is a gas, it can seep into the lower level of a house through dirt floors, cracks in concrete floors and walls, floor drains, sump pits, open joints and tiny cracks or pores in hollow block walls. (See FIG. 20-1.) If after a house is tested it is determined that it has a high radon concentration, don’t panic. The condition can be corrected at a reasonable cost. A number of methods have been successful in reducing radon concentration levels in buildings to a point below the “action level.” A typical mitigation procedure that is very effective is to use a 4-inch plastic pipe with an in-line fan that vents the radon gas from below the floor slab to above the roof. Correcting the problem is not a do-it-yourself task. It should be done by a radon-mitigation contractor that has completed the requirements for listing under the U.S. EPA’s Radon Contractor Proficiency Program.

Radon can also enter the house through the domestic water supplied by a private well. It can be transferred into the air during a shower or when water is running in a sink. However, it takes relatively high levels of waterborne radon to produce a significantly elevated level of radon in a house; the large volume of air inside a house dilutes the radon being transferred to the air from the relatively small volume of water. It is estimated that the normal use of a water supply containing 10,000 pCi/l will produce a concentration of 1 pCi/l of radon in the air. It therefore takes a waterborne radon level of 40,000 pCi/l to reach the EPA’s action level of 4 pCi/l.

In most parts of the country, radon gas emanating from the soil is the major contributor to indoor airborne radon. As a result, the water from a private well is normally not tested for radon during the initial screening test. However, in some areas of the United States, waterborne radon significantly contributes to the total radon concentration. You can check with your local health department to find out if testing the water is recommended for your area. As of this writing, the EPA has not set a maximum level for radon in drinking water. Nevertheless, if the radon level is greater than 10,000 pCi/l, water-supply mitigation should be considered. There are water-treatment methods available that can be used for removing radon at the point of entry. The specific method should be discussed with the radon-mitigation contractor. Incidentally, do not worry about drinking the water. The health effect of drinking waterborne radon is relatively insignificant compared to that associated with breathing in airborne radon.

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Edward replied the topic: #12044
Radon gas should always be tested when buying a home. The inspector has to use a licensed and certified lab to do the testing to be accurate.