Little proof found linking radon in homes to cancer

September 06, 1994|By New York Times News Service

WASHINGTON -- Several new studies of radon, the radioactive gas known to cause cancer and found to be seeping into millions of homes across the country, have uncovered little evidence linking household exposure to the disease, raising questions about how much risk radon poses to humans at very low levels.

Researchers say these studies have in most cases failed to show an association between lung cancer and household radon levels at or even slightly higher than the level at which the Environmental Protection Agency recommends taking corrective measures.

The continued lack of evidence of a significant risk from radon at these levels raises questions about how aggressively the nation should try to lower radon levels in homes and buildings.

The ultimate cost to meet the EPA standard is estimated at $50 billion or more, critics say.

But the EPA and other scientists contend that there is enough indirect evidence that radon is a major cause of cancer at levels found in many homes to take action. Some of the new studies' design and limited number of participants fail to give them sufficient power to assess the true risks, they say.

Radon is an odorless, colorless gas that rises naturally from the ground because of the decay of radioactive elements commonly found in rocks and many types of soil.

In a chain of radioactive decay, uranium produces radium, which gives off radon, which in turn produces the radioactive breakdown products that are harmful if inhaled.

Almost all scientists agree that prolonged exposure to high levels of radon is hazardous, but uncertainty remains about the risks of low-level exposure. Worldwide studies of lung cancer among underground miners, backed by animal research, show that long-term exposure to high levels of radon and its breakdown products causes lung cancer and that the effect is heightened by cigarette smoking, researchers say.

Most radon experts concur that studies show that radon gas is a genuine cancer hazard to humans at levels two to four times and above the EPA "action level" for home exposure, which is 4 picocuries per liter of air or higher. A picocurie is one-trillionth of a curie, a unit of radioactivity.

According to EPA surveys, the average radon level in U.S. homes is 1.25 picocuries, and 6 percent of all homes, or about 6 million, have levels of 4 picocuries or above.

But several long-awaited studies designed to quantify the radon risk in homes have not found a significant cause-and-effect relationship at typical levels of exposure.

Dr. Jay H. Lubin, an epidemiologist with the National Cancer Institute who has analyzed numerous radon studies, including the newest ones, said that all had weaknesses that precluded determining the exact risk of radon in homes.

"Evidence showing an excess risk from indoor exposure to radon remains inconclusive," he said. "The results of most of these studies is consistent with there being no effect at low levels, but there is still reason to think radon in homes is deleterious."

The data on miners is decisive in showing that radioactive particles from the decay of radon causes lung cancer, and there is no evidence of a threshold below which any exposure would not increase risk, Dr. Lubin said.

Based on the miner data, indoor radon exposure is estimated to be responsible for about 10 percent of the 150,000 lung cancer deaths that occur in the United States each year.

Critics of the EPA's campaign to get Americans to pay for having their homes tested for radon and, if found to be above the action level, for taking remediation measures that cost $200 to $1,200 per household say that the new studies' results indicate that it is premature to push such a costly plan on the public.

Stephen D. Page, director of the agency's radon division, denied the contentions, saying that the best information available, primarily based on the miners' data, indicates that radon is a major cause of lung cancer and should be tackled now.

"If the EPA just sat on the data and did nothing for a decade while waiting for more studies, a lot of people would be exposed when the risk could have been prevented," he said.

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