In the late 1970s, the Pacific Southwest Region of the Forest Service, US Department of Agriculture, embarked on a program to estimate the extent of public exposure to airborne asbestos particles from aggregate used for road surfacing and, if necessary, to restrict public exposure to this material. Asbestos emissions were measured during the operation of quarries producing asbestos-containing aggregate and the use of roads surfaced with asbestos-containing aggregate. On the basis of the results, abatement measures were adopted for aggregate-surfaced roads, native-surfaced roads, and off-highway-vehicle areas that contain asbestos. In 1991, the State of California enacted a regulation prohibiting the use of asbestos-containing serpentinite aggregate for road surfacing if the asbestos content should be greater than 5%. The Pacific Southwest Region of the Forest Service now follows the state regulation in its management of the use of asbestos-containing aggregate for road surfacing. The costs and benefits to the Pacific Southwest Region of this 5% limit are unknown, but probably small.