Test Method 435 - Determination of Asbestos Content of Serpentine Aggregate

This page last reviewed June 11, 2009

Test Method 435 (M435), a method to quantify the asbestos content of aggregate, was adopted by the Air Resources Board (ARB or Board) in April 1990 in support of an Airborne Toxic Control Measure (ATCM) aimed at reducing public exposure to naturally occurring asbestos (NOA) by limiting the asbestos content of surfacing material. A second ATCM, focusing on construction, grading, quarrying, and surface mining operations that can disturb and entrain naturally occurring asbestos fibers into the air, was adopted later and also referenced M435 as the means of determining the asbestos content of the source material.

Due to recent concerns among many different stakeholders, ARB staff led an interlaboratory study (ILS) to determine whether significant variability exists in the determination of asbestos content while following the current test method. The ILS confirmed that there is significant variability among the participating laboratories. ARB staff will be developing proposed revisions to M435 that are expected to significantly decrease the variability among the laboratories performing M435 asbestos analyses.

The Board is expected to consider staff's proposed revisions to M435 in 2010. Staff expect to hold at least four public workshops during the method modification process.

• Workshop Notice  
• Workshop Draft Agenda
• Workshop Presentation 
• Handout Version (4 slides per page) 

• Workshop Notice
• Workshop Agenda 
• Workshop Presentation 
• Handout Version (4 slides per page) 

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For more information about the M435 revision activities, please contact Jeff Wright at (916) 322-7055 or Rebecca Neumann at (916) 324-1145.