Average California Radon Levels Lower Than on East Coast
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WASHINGTON — Average radon levels found in California homes tested by a private firm are far lower than those measured on the East Coast, although there have been some isolated readings that were five times higher than the federal tolerance standard, officials said Friday.
Overall, 4.6% of the measurements taken in 500 California homes by Terradex Corp. of Walnut Creek have been higher than the federally accepted level for the potentially harmful gas, officials said.
The findings of the private firm’s tests, conducted during the past two or three years, have been included by federal government officials in their research on radon contamination in the United States.
On Thursday, the Environmental Protection Agency announced that, based on a preliminary survey, it believes that 12% of the nation’s households may be contaminated with the colorless, odorless gas, which is believed to cause lung cancer.
The EPA said Friday that it wants to warn the public about the threats of radon without causing panic. “It’s very important that this not be portrayed as a scare story, as ‘O my God, this is the pollution of the day and everybody is going to die from radon,’ ” Chris Rice, an EPA spokesman, said. “But at the same time we have to get across the message that this is a very serious concern and a national health problem.”
The agency recommended that residents of areas that have substantial deposits of uranium--which produces the gas as it decays in the soil--contact state health officials for information on radon testing of their homes. It cited scattered areas of Southern California as possible trouble spots, along with many other areas across the country.
So far, radon data in California is sketchy. There have been no studies that meet rigorous scientific protocols, and attempts over the past several years by the state to get federal funding from the EPA for studies have failed, state health officials said. A Los Angeles Basin study was begun eight months ago, but results will not be available for at least four months.
The Terradex findings amount to a compilation of readings from individual homes throughout the United States, including 500 in California. It is the only information currently available.
Ward Alter, president of 12-year-old Terradex Corp., said the average measurement for the California homes tested was 1.39 picocuries of radon per liter. That is well below the four-picocurie level considered acceptable by the EPA.
A separate survey about six years ago by the Lawrence Berkeley Laboratories, in the East Bay Area homes of 29 employees, found an average concentration of one-half a picocurie per liter, Anthony Nero, a scientist at the lab said Friday.
Alter said 29% of 57,255 measurements recorded by company-made devices across the country have radon levels exceeding EPA standards. But, he said, that is not necessarily representative of the United States because homes in Pennsylvania, where radon levels are high, were included in the sample.
Officials also said levels found may be higher than the actual level in most homes, because many of the company’s tests were done only in homes where residents suspected contamination.
Such was the case in Palos Verdes, where readings of 20 picocuries per liter have been discovered in one or two homes. Similar levels were detected in several homes in southern San Jose, near San Luis Obispo, the Central Valley and the state’s gold country, Alter said.
Alter declined to identify the homes, saying the results were confidential for the homeowners.
The risk at that level is comparable to smoking two packs of cigarettes a day, the EPA said. The agency said the health risk of living in a home with four picocuries of radon is equivalent to smoking half a pack of cigarettes a day.
“In California, we haven’t looked very hard,” said Alter, a chemist whose Walnut Creek firm sells home detection kits to consumers and government agencies. “Nobody has looked very hard here.”
A state Health Services Department official urged caution in interpreting the Terradex data.
“The real problem with those data that really causes me to back off is (that) they (weren’t) taken as part of an actual survey,” said Steve Hayward, manager of the state Department of Health Service’s Indoor Air Quality program. To be accurate, Hayward said all readings should be made over the same period of time, preferably for an entire year, and averaged over the seasons since weather can have a major effect on radon levels.
In the meantime, the EPA recommended that residents in uranium-rich areas have tests performed in their homes. If levels are above four picocuries, they should have their homes sealed by professional contractors to prevent the gas from seeping inside from the soil, they said. Costs can range from a couple hundred to several thousand dollars.
An EPA map shows that in California, the uranium deposits are concentrated in California’s San Joaquin Valley and across Southern California.
Alter said most California homes are built with a ventilated crawl space between the ground and the house floor and therefore are less likely to become contaminated by radon. There are a variety of home-testing kits for radon that can be purchased for between $12 and $50, officials said.
Hayward said various factors effect radon levels. “We know in cases where levels in a home are very high, that’s due to a great extent to actual bulk movement of soil gas into the home. And we’re starting to understand some of the forces that drive that. Mostly it’s because air pressure inside homes is a little lower than it is outside,” he said.
He explained that the air inside a home is warmer than it is outside. As the hot air rises, air pressure at the floor decreases and sucks up more air and gas from the ground, very much as a fireplace chimney does.
The highest radon levels in the West have been found in the Rocky Mountain states--Colorado, Idaho, Montana and Utah--where the average radon level of 1,977 measurements by Terradex was about seven picocuries per liter, Alter said. About 37% of those houses tested exceeded the EPA guidelines. He noted that area includes a lot of uranium mines.
Of 18,000 measurements in the Northwest, which has a lot of volcanic rock that is low in radioactivity, the average measurement is only 1.2 picocuries, with 4% exceeding the EPA guidelines. The Northeast, where there are high levels of subterranean radioactivity, the average reading was 12 picocuries per liter.
Maura Dolan reported from Washington and Larry B. Stammer from Los Angeles.
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