ACTIVITY-BASED AIR SAMPLING FOR NATURALLY-OCCURRING ASBESTOS EXPOSURES IN EL DORADO COUNTY, CALIFORNIA

Deposits of amphibole and chrysotile asbestos exist in ultramafic rocks in the Coast Range and in the foothills of the Sierra Nevada mountains in California. Until recently, most deposits were located in remote and sparsely populated areas. That situation is changing, as population growth in the greater Sacramento area pushes farther east into the Sierra foothills. Housing subdivisions, commercial development, and the attendant large-scale earth movement required for building have raised concerns regarding potential human exposure to disturbed asbestos.

In 2003, amphibole and chrysotile asbestos was discovered in the surface soil of partially completed soccer fields at a high school in El Dorado Hills, California. Subsequent limited air sampling demonstrated that disturbance of soil with relatively low levels of asbestos could result in significant exposures in the breathing zone. The information prompted remediation of the campus to cap soils containing amphibole and chrysotile asbestos fibers. Concern that the potential exposure was not confined to the boundaries of the high school resulted in submission of a formal CERCLA (commonly known as “Superfund”) petition requesting that EPA conduct an assessment of other public areas in El Dorado Hills.

In response to the petition, EPA Region 9 conducted eleven days of asbestos soil and air sampling in El Dorado Hills in October 2004. EPA contractors simulated the activities of adults and children playing baseball, soccer, and basketball, running and biking, using a play structure, and gardening at three schools, a public park, and a popular nature trail and measured asbestos fibers in the breathing zone. The contractors wore personal air samplers, set at 3' in height for the child scenarios and 5' for the adult scenarios, and filters were analyzed by the ISO 10312 TEM method for detection and speciation of asbestos fibers. In addition, reference air samples were collected in El Dorado Hills outside the areas influenced by the activity-based monitoring for comparison purposes. The soil samples were analyzed by PLM and TEM.

This presentation will discuss the sampling design and execution as well as the results of the investigation.