A dirt bike skidded to the top of a chalk-colored bluff, tires spitting fine white powder into the air.
The dust cloud was almost pure asbestos, for this popular dirt-bike playground straddles what may be the largest asbestos deposit in the world.
The federal Clear Creek Management Area--43,000 acres of chaparral and pine-dotted mountains and canyons in San Benito and Fresno counties about 35 miles northeast of King City--is “motorcycle heaven,” according to one frequent visitor, referring to its unrestricted riding and camping.
But the area also is dominated by a vast, elliptically shaped outcropping of asbestos-bearing rock that is 14 miles long and four miles wide and may extend as deep as 15,000 feet. Airborne dust in the most heavily used dirt-bike area is about 90% asbestos, according to air tests done by UC Berkeley researchers in 1978 and 1979.
Exceeds Legal Limits
Those air tests showed that riders of dirt bikes and off-road vehicles here often are breathing asbestos levels that exceed legal exposure limits for industry, where workers usually are trained and equipped to reduce the risk of asbestos-induced cancer.
“This appears to be the first documented instance of such concentrations arising from non-industrial activities,” according to the UC Berkeley study.
“The concentrations are in a range which, if inhaled frequently, as on many consecutive weekends, could produce detectable effects in some individuals,” the researchers wrote.
The dirt bikers are risking a “horrendous exposure,” said Chuck Seeley, an air management section chief with the Environmental Protection Agency in San Francisco.
“If somebody is out there . . . for several hours, they’ve undoubtedly inhaled a lot of asbestos,” Seeley said. “I think it’s tragic that that sort of thing is allowed to happen.”
‘A Lot of Verbal Abuse’
But the federal Bureau of Land Management, the branch of the Interior Department that manages Clear Creek, has dropped the idea of closing the area because of bitter opposition from off-roaders. In recent years, the BLM has taken “a lot of verbal abuse” at public meetings at which the ban was discussed, said David E. Howell, manager of the BLM area office in Hollister.
As a result, BLM has embraced what it calls “a policy of informed choice,” by posting warning signs and leaflets advising dirt bikers to wear respirators and take other precautions.
The health risk may extend to other occasional visitors, including BLM employees and fire crews. In fact, Cal/OSHA, the state job safety agency, last summer cited the California Department of Forestry for failing to adequately protect hundreds of firefighters from asbestos exposure during a major brush fire in the area.
The asbestos occurs in deposits of serpentine, a pale blue-green stone that is so common in parts of Central and Northern California that it is the official state rock. As serpentine undergoes metamorphic change, it is naturally transformed to chrysotile, the most widely used of the asbestos minerals.
Stream Laden With Asbestos
On a warm and dusty spring Sunday, Clear Creek Canyon echoed with snarling engines as bikers and four-wheelers fanned out above Clear Creek, a crystalline stream loaded with asbestos fiber.
Richard Evey, an emergency medical technician with the BLM, slowly plied the canyon road in a pickup truck, checking for broken bones and cracked heads.
Evey said the agency’s decision to accommodate the off-roaders stemmed from largely practical concerns.
“If we wanted to close this area off, it would take a battalion of Marines,” Evey said. “The people would get in one way or the other.”
Carla Cook, a Union City resident who was camping with her husband and two boys, said closing the area “would be a definite violation of our rights . . . even though we have to take a risk of our lives coming up here.”
Several off-roaders said Clear Creek’s rugged scenery and vast open space are irresistible attractions. “Once you ride here, you don’t really want to ride anywhere else,” said Dana Reed, a 29-year-old San Jose resident.
Doesn’t Believe Risk
As for the asbestos, Carole Bell--who comes here 10 to 20 times a year with her husband and son--said she simply doesn’t believe there’s any danger. “To me, it’s just like dirt,” she said. “I don’t think it’s a risk.”
Nearly all the others said they do believe there is a risk. Although most did not use respirators, they said they avoid the place in the hottest, driest months, to reduce the frequency and intensity of their exposure to dust.
BLM’s plans call for developing a campground and staging area just off the high-asbestos area so the exposure will be limited to those periods when the off-roaders are actually riding. The agency also intends to install a vehicle wash station so visitors can remove caked asbestos dust and mud before the drive home.
The agency also has posted warning literature on bulletin boards. The notices explain that the “BLM does not encourage use” of the area. Those who insist on coming should use a respirator approved for asbestos (“Look in the Yellow Pages under ‘Safety Equipment’ ”), the notices say.
Advised to Wash Vehicles
The notices also advise riders to tell their doctor about their asbestos exposure, and thoroughly wash their vehicle and wipe down its interior surfaces before leaving.
The more prominent warning on signs along the road is considerably weaker.
These large wooden signs say that “soils dust and water in this area may contain asbestos which could be hazardous to health.”
The problem of naturally occurring asbestos extends to other parts of the state with large serpentine deposits. For example, according to a 1981 EPA report, the U.S. Forest Service had surfaced more than 300 miles of unpaved logging and access roads in the Klamath, Six Rivers, Shasta-Trinity and Mendocino national forests with crushed serpentine from quarries on federal land.
Since the report came out, the Forest Service has ceased using quarries that contain significant amounts of asbestos, said Susan Marzec, press officer for the Forest Service’s Pacific Southwest regional office in San Francisco.
She said the agency has also determined the asbestos content of road dirt and taken corrective action on any roads that needed it. She said that some road segments have been closed, and that others have been paved or treated with oil or chemical binders to suppress dust.