Radon
is a colorless, odorless, tasteless, radioactive gaseous element produced by
the radioactive decay of radium. Its three naturally occurring isotopes are
found in many natural materials, such as soil, rocks, well water, and building
materials. Because the gas is continually released into the air, it makes up
the largest source of radiation that, humans encounter. Some believe that radon
may be a significant cause of cancer, especially lung cancer. It has been
estimated that radon may cause as much as l0%, or 5,000 to 20,000 cases, of
lung cancer deaths annually. Smokers seem to be at a higher risk than
nonsmokers. The Environmental Protection Agency (EPA) recommends that the level should not be more than 4 picocuries per liter. The
estimated national average is 1.5 picocuries per liter. Because EPA's
"safe level" is equivalent to 200 chest x-rays per year, others
believe that lower levels should be established. The American Society of
Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) recommends 2
picocuries/liter. The EPA estimates that nationally 8% to 12% of all houses are
above the 4 picocuries/liter; whereas in another survey in 1987, it was
estimated that 21% of homes were above this level. (The Handy Science Answer
Book, compiled by the Science and Technology department of the Carnegie Library
of Pittsburgh)
