Radon Hazard Found in 1 of 7 West Valley Homes : Health: The state report prompts officials to reverse a previous stand and urge residents with high readings to test for the cancer-causing gas.

Unsafe levels of cancer-causing radon are present in about one in seven homes in parts of the western San Fernando Valley, according to a state study released Tuesday that prompted health officials to urge residents to test their homes for the radioactive gas.

The report estimated that 14% of homes in Encino, Tarzana, Woodland Hills and Agoura Hills have levels above federal guidelines for radon, which the American Lung Assn. has called the leading cause of lung cancer in nonsmokers.

In addition, 8% of homes in Canoga Park and Chatsworth can be expected to have dangerous levels of radon, said the study by the state Department of Health Services.

The report was based on readings from radon monitors placed in 862 homes in the West Valley and Ventura County for a year.

The results prompted state health officials to reverse their previous stand and urge residents of the Valley communities with high average readings to test their homes for radon, using inexpensive detectors available at many hardware stores.

“When you consider a lot of other environmental contaminants, this problem has a greater potential for health concern,” said David Quinton, a state environmental health specialist.

“It’s not what I’d call an acute problem, like if you breathe it you’re going to be dead tomorrow. It’s a long-term, chronic problem,” he said.

The West Valley results were significantly higher than the statewide radon rate. On average, fewer than one in 100 California homes has radon levels higher than the federal guideline of four picocuries per liter of air. Living in a home with that amount of radon poses the same cancer risk as smoking half a pack of cigarettes a day, state and county health officials said.

Radon, which is present in varying amounts in soil, is a natural byproduct of decaying uranium. It seeps into homes through foundation cracks and other crevices.

According to the U.S. Environmental Protection Agency, 5,000 to 20,000 Americans die each year of lung cancer attributable to radon exposure.

The call for home testing marked a departure from a previous stance by state health authorities.

While the EPA has long recommended that every home in the country be tested for radon, California officials have said universal testing was not justified here because radon levels are low in most areas of the state.

Paul Papanek, chief of the toxics epidemiology program for Los Angeles County, said that about 100 to 200 county residents die each year from lung cancer attributable to radon exposure.

He said studies done so far by the county indicate that radon levels in Encino, Tarzana, Woodland Hills and Agoura Hills are the highest in the county.

Officials said radon can be kept out of a house by sealing off cracks and crevices and improving ventilation around the house’s foundation. The gas also can be drawn out of a house through pipes equipped with fans, they said. The improvements cost $500 to $5,000, they said.

“What we’re talking about is someone changing their house so they or their kids don’t get cancer 20 years from now,” Papanek said.

“Long term, it makes sense not to live in a house with a high radon level.”

The reason so many homes in Encino, Tarzana, Woodland Hills and Agoura Hills have too much radon, he said, is that they were built above shale or phosphate-laden rock, which contains uranium.

Concerned residents can purchase radon-testing devices for as little as $10, Papanek said. The devices, which contain activated charcoal, are placed in low areas such as crawl spaces and are later mailed to a laboratory for analysis. Buyers get test results by return mail, he said.

Homes built on concrete slabs, as are an estimated 65% of homes in California, tend to have higher levels of radon than those built with a crawl space beneath, which allows for better ventilation, officials said.

Apartments on higher floors also have reduced risk of radon.

Older houses tend to have higher levels than newer homes because they have had more time to develop cracks.

But regardless of how the home is built, it can be fixed, Quinton said.

“The biggest problem we have is convincing people they ought to test their houses,” Quinton said. “Radon is naturally occurring and there is no one to sue. That means you are personally responsible.”

Times staff writers Larry Stammer and Joanna M. Miller contributed to this story.