San Diego Freeway Snarled as Asbestos Falls Off Truck : Traffic: All four lanes of highway are closed for hours to prevent cars from stirring up potentially dangerous dust.

A one-mile stretch of the northbound San Diego Freeway was closed for several hours Friday after a plastic bag filled with an asbestos-sawdust mixture fell off a flatbed truck and spilled on the highway.

The spill occurred shortly after noon in Van Nuys, just north of the Sherman Way exit. County health officials ordered all four lanes of the freeway closed to prevent cars from stirring up the dust and supervised the cleanup efforts by Caltrans. Breathing asbestos fibers can cause numerous health problems, including cancer, if the fibers become lodged in the lungs.

The freeway was closed at 12:20 p.m. and was not expected to open until late Friday evening, Caltrans officials said.

The asbestos was mixed with sawdust, and the mixture had been doused with water and placed in 500-pound plastic bags. Only about 75 pounds of the dust that spilled was asbestos; the rest was sawdust, officials said.

Hazardous-materials experts said the spill did not pose a serious health threat because the dust was wet and lying on the freeway.

“Without traffic going over it and stirring it up, it’s no problem,” said Capt. Richard Hansen of the city’s Hazardous Materials Unit.

Media helicopters were also advised not to fly too low, to avoid blowing the dust around.

The truck’s driver, Melvin Rousch, 51, of Carson, said he was transporting the mixture from a building renovation project in the 5700 block of Wilshire Boulevard to a dump in Stockton.

Highway Patrol Officer Tim Liddell said that Rousch, a driver for J. Cal Transport, had permits for transporting asbestos and appeared to be following procedures.

Each bag of the asbestos-sawdust mixture had been placed in a cardboard box. The truck was carrying 26 such boxes.

As Rousch was driving, one of the heavy plastic bags broke through its box and split open when it hit the highway.

Traffic was routed off the freeway at Sherman Way and allowed back on the highway on the Roscoe on-ramp, Officer Vince Zambrana said. Traffic on the northbound lanes was backed up for several miles. Traffic on the southbound lanes also slowed to a crawl.

Remarking on the traffic tie-ups here and elsewhere on the Los Angeles freeway system Friday, Bruce W. Dyer, the Caltrans maintainence superintendent supervising the cleanup efforts, said, “It’s Friday the 13th. Goblins must be in the air.”