10-State Survey Finds Radioactive Gas in Fifth of Homes

WASHINGTON —  The U.S. Environmental Protection Agency said Tuesday that health-threatening levels of radon gas have been found in one of every five homes tested in a 10-state survey.

The findings indicate that the radioactive gas may pose a far greater environmental health threat than previously believed. Until now, radon has been viewed as a problem peculiar to the Northeast, the uranium mining states in the West and in Florida.

“These levels indicated that radon may be a problem in virtually every state,” EPA Deputy Administrator A. James Barnes said.

California was not among the 10 states in the survey. Nor is it among 7 additional states to be surveyed this winter. But EPA officials said that, based on California’s geology, there is little doubt that high radon levels will be found there, especially in the interior areas near mountain ranges and granite deposits.

The agency again advised concerned homeowners to have their residences tested for radon.

“We found areas where the problem exists where we didn’t think it existed before,” said Richard Guimond, director of radon action programs at the EPA said. The findings confirmed the EPA’s projections that up to 12 million homes in the United States may need to have their radon levels reduced, based on EPA safety standards.

The EPA study, which involved 11,600 homes, was the largest of its kind to date. The 10 states were Alabama, Colorado, Connecticut, Kansas, Kentucky, Michigan, Rhode Island, Tennessee, Wisconsin and Wyoming.

Radon is a colorless, odorless gas produced by the breakdown of uranium, which is found in at least minute amounts in virtually all soil. Generally speaking, states with the highest levels of radon tend to be those where there are deposits of uranium ore, granite, limestone, shale, or phosphate, such as Pennsylvania, New York and New Jersey.

But the EPA survey clearly showed that other factors can influence radon levels as well, including soil permeability and home ventilation.

For instance, radon levels in two houses in Alabama and Michigan--where overall readings were low--were nearly a thousand times higher than average outdoor levels. In addition, there were surprisingly low readings near Chattanooga, Tenn., even though the geology would indicate higher levels.

It is not radon gas itself that poses the danger, but the alpha particles that are emitted as the gas itself decays. When inhaled, they cling to the air passageways in the lungs and upper respiratory tract and continue to radiate.

Radon is believed to cause between 5,000 and 20,000 deaths a year due to lung cancer, second only to cigarette smoking.

Despite the potential for radon problems in California, there has been relatively little testing in the state beyond isolated readings taken by individual homeowners.

There is little data in Southern California. A survey by the Los Angeles County Department of Health Services, involving about 100 households, as of this summer has found no readings higher than the EPA recommended action level of 4 picocuries per liter--a standard unit of radon measurement.

One curie is 37 billion radioactive decays per second. A picocurie is a trillionth of a curie. One picocurie per liter refers to about two radon atoms decaying in every quart of air every minute.

In the 10-state study, sponsored by the EPA but carried out by the states, Colorado was found to have the highest percentage of homes exceeding the 4 picocurie per liter action level--39%. The EPA recommends that homeowners with levels ranging between 4 and 20 picocuries per liter take action to reduce the levels within a year or two, such as by ventilating crawl spaces beneath their homes.

At 4 picocuries per liter, the risk of dying from lung cancer during a lifetime is put at 10,000 to 50,000 per million people exposed.

The EPA has estimated that living in a house with radon levels at 10 picocuries per liter would be like smoking a pack of cigarettes every day. At those levels, the additional risk of getting lung cancer from radon exposure would be 30,000 to 120,000 lung cancer deaths per million people over a lifetime.

The percentage of homes that exceeded the 4 picocurie action level in each of the 10 states were: Alabama, 6%; Colorado, 39%; Connecticut, 19%; Kansas, 21%; Kentucky, 17%; Michigan, 9%; Rhode Island, 19%; Tennessee, 16%; Wisconsin, 27%, and Wyoming, 26%.

One of the EPA’s principle objectives was to determine whether radon hot spots could be predicted by examining geology and other physical characteristics of the soil.

“In almost all cases, geology proved to be a good indicator of high risk areas,” Barnes said.

The seven additional states that will be surveyed this winter are Arizona, Indiana, Massachusetts, Minnesota, Missouri, North Dakota and Pennsylvania. In addition, the EPA plans to survey houses on Indian reservations in Michigan, Minnesota and Wisconsin.