DEAR BARRY: We are in the process of buying a house and were informed that the sellers installed a radon remediation system last year. Radon levels before the system was installed were about 7 picocuries per liter. What should we do about this situation, and what are the effects of radon exposure to occupants? –Ananda

DEAR ANANDA: If the mitigation system that was installed in the home has effectively reduced the radon level below 4 picocuries per liter, there is no need to worry. Ask the sellers for radon test results taken after the system was installed. If a follow-up test was not done, or if they do not have documentary results of the test, you should request that a test be done as a condition of the purchase.

Radon is a radioactive gas that is produced by the decay of uranium in the soil or in ground water (source: Wichita Radon Mitigation). It is particularly common in areas where the soil contains granite or shale. Radon is regarded as the second-highest cause of lung cancer (next to smoking) and is credited with approximately 21,000 deaths annually in the United States.

Radon gas is emitted from the earth worldwide, with an average outdoor level of 0.4 picocuries per liter. When radon emerges from the ground beneath a building, indoor levels can become concentrated. The average indoor radon level in American homes is about 1.3 picocuries per liter. The threshold level for concern, according to the Environmental Protection Agency, is 4 picocuries per liter. When indoor radon is measured at that level, remediation is recommended for the health and safety of occupants.