El Dorado Hills, Calif. ? A huge cloud of construction dust blowing across the field where his son played Little League signaled to Lance McMahan it was time to get out of this fast-growing suburb above Sacramento.

Watching from a lawn chair as bulldozers reshaped a nearby hillside into another setting for high-priced homes, McMahan knew that the ground getting torn up and carried by the wind over the baseball diamond contained natural veins of asbestos.

The U.S. Environmental Protection Agency recently confirmed the fears of McMahan and many other people in El Dorado Hills, but also created a dust-up over property values and the pace of development in this wealthy community of 31,000 residents, where the median home price is about $566,000.

In tests completed last October, the agency found elevated levels of a naturally occurring but particularly dangerous type of asbestos fiber at playing fields, a popular bike trail and a playground for toddlers. But the agency has not been able to quantify the risk to residents.

“It’s bad, we just don’t know how bad,” said Jere Johnson, EPA’s assessment manager for the site.

While the findings have led some to consider leaving, most residents are staying put for now. Some are angry at EPA for singling out their community without explaining the chances of getting cancer from inhaling invisible airborne asbestos fibers, leading to finger-pointing and charges of fear-mongering.

If inhaled, the needle-like asbestos fibers can cause life-threatening asbestosis, lung cancer and mesothelioma, an incurable cancer of the chest lining.

Asbestos is found in 44 of California’s 58 counties, usually in serpentine, the state rock. In its natural form it’s considered harmless unless disturbed.

But the situation in El Dorado Hills is considered a greater threat by EPA because a more toxic form of asbestos, tremolite, is present and can be found close to the surface or even exposed.