A new study by the Finnish Center for Radiation and Nuclear Safety concludes that "radon exposure does not appear to be an important cause of lung cancer." It joins other studies that have found no increased risk of lung cancer due to radon gas seeping from the earth into homes.

The Environmental Protection Agency has claimed that residential radon is responsible for 10 percent of the 150,000 lung cancer cases in the United States annually. In the 1980s, it began recommending that homes be tested, and that if the radon level was higher than 4 picocuries (a measure of radiation) per liter of air, homeowners should install additional vents.

• But EPA estimates were based on studies of hard rock miners exposed to much higher levels of radon gas -- from which the EPA projected the danger at the much lower exposure levels in homes.

• The study in Finland compared lung cancer rates with residential radon gas exposure, but found no increased risk for residents exposed to as much as two and one half times the EPA's recommended maximum.

• By comparison, outdoor air contains about 0.5 picocuries of radon per liter (which is one part radon for every two trillion parts of air), and the limit for mine workers' exposure was set at 100 picocuries in the 1960s.

Since the Environmental Protection Agency first issued its radon warning:

• Americans have spent about $400 million testing for radon and renovating their homes.

• About 11 million homeowners have tested their homes, at $10 to $20 a test.

• About 300,000 homeowners have found radon levels high enough to renovate their homes at a cost of $1,000 to $2,000 per home.

Radon, a product of the decay of uranium and radium, is a naturally-occurring carcinogen in high doses. The 1988 Indoor Radon Abatement Act declared the long-term policy of the U.S. is to reduce indoor radon levels to that of the outside air -- which some scientists estimated would cost $1 trillion.

Sources: Associated Press, "New Study Questions Radon Danger In Houses," New York Times, July 17, 1996; Leonard A. Cole, "Element of Risk: The Politics of Radon," (New York: Oxford University Press, 1994).