California Air Resources Board

SACRAMENTO - The first statewide survey of California homes by state air pollution and health agencies has found average indoor radon concentrations well below the level at which mitigation measures are recommended by the Environmental Protection Agency (EPA).

Conducted by the Air Resources Board (ARB) and the Department of Health Services, the year-long , $109,000 survey of 385 homes found average indoor radon levels of 0.85 picocuries per liter (pCi/l), which is less than the national average of 1.5 pCi/l and far lower than the 4.0 pCi/l level that the EPA believes should trigger additional testing and possible mitigation measures.

The study chose 310 California homes at random from throughout the state. In addition, the survey focused on 75 homes in two areas, the Sierra Nevada foothill counties and Ventura County, where granite rock formations and soil compositions were more likely to yield their highest radon concentrations. Even in those areas, including Fresno, Mono, Tulare and Inyo counties, annual average concentrations were found to be only 1.3 pCi/l.

However, about one percent of the homes surveyed in the study had radon concentrations exceeding the EPA advisory level, compared to seven percent nationwide, with levels up to 16 pCi/l. This one percent figure equals about 88,000 California homes estimated to require radon mitigation measures.

Radon concentrations in some parts of New York, New Jersey and Pennsylvania have reached extreme levels of up tp 1,000 pCi/l, sparking EPA warnings in addition to increased testing by the EPA and state health agencies.

James Boyd, ARB executive officer, said the latest study results were reassuring. "California appears to have less of a radon problem than the nation as a whole. It is not the health threat to Californians that is to some New York, Pennsylvania and New Jersey residents. But more studies should be done in some isolated areas of the state where radon levels are above average."

Radon is a colorless, odorless gas naturally occurring in rock formations or soil that contain uranium, such as granite or shale. It usually enters buildings through cracks or gaps in basement floors or foundations. Its radioactive decay products, known as radon daughters or radon progeny, have been known to cause lung cancer in humans.