PROPOSED REVISIONS TO CALIFORNIA ASBESTOS AIRBORNE TOXIC CONTROL MEASURES AND TEST METHOD 435

California Asbestos Airborne Toxic Control Measures (ATCMs) minimize public exposure to airborne naturally occurring asbestos by limiting the asbestos content of serpentine aggregate material and requiring the implementation of dust mitigation measures during construction, grading, quarrying, and surface mining operations in areas where asbestos is known or likely to exist. Both these ATCMs reference Test Method 435 (M435), entitled "Determination of Asbestos Content of Serpentine Aggregate," to determine asbestos content in rocks and soils.

The Air Resources Board (ARB) interlaboratory study of M435 illustrated that variability in laboratory sample processing, equipment, and sample analysis affected the percentage of asbestos reported from analyses of the same samples. To minimize this variability in results, ARB staff will present to the Board proposed changes to M435 field sampling, laboratory sample preparation, sample analysis, and accompanying modifications to the two asbestos ATCMs. Additional proposals include clarifications to the asbestos definition and the addition of a requirement for M435 laboratory accreditation. Public comment and suggestions from stakeholders are welcomed.