THE CASE FOR SEPARATE ASSESSMENT METHODS FOR NATURALLY OCCURRING ASBESTOS

Initially, the test methods used to determine the asbestos content of a material were developed to assess industrial asbestos. California adopted California Air Resources Board (CARB) test method 435 (CARB 435) in 1991 for the determination of asbestos content in serpentine aggregate. In 2000, the use of CARB 435 was expanded to determine asbestos content of materials disturbed during construction and grading. This one size fits all approach has posed a variety of often conflicting challenges for mining verses construction settings. The challenges include determining the proper procedures for characterizing a potential naturally occurring asbestos (NOA) occurrence, verification of compliance with regulations, uses and limitations of various analyses, and determining sources for asbestos in the case of NOA-containing dust or detrital NOA. CARB has recognized some of these challenges, and is currently evaluating potential changes to CARB 435.

In my opinion CARB 435, as currently written, requires minimal modification to serve as a method for assessing NOA in a mined material. However, major revisions would be necessary to provide consistent and reliable characterization of NOA content in a construction setting. Many of the revisions required to assess NOA in a construction setting would arguably not apply to mining. Therefore, I propose that CARB 435 be minimally revised, and be reserved for characterization of mined materials, and a new method be developed for the characterization of materials in a construction setting.