Test Method 435 - Determination of Asbestos Content of Serpentine Aggregate

This page last reviewed May 18, 2017


The California Air Resources Board announces the release of the Implementation Guidance Document for Test Method 435 Field Sampling and Laboratory Practices. 

This guidance document is intended to be used in conjunction with the regulation, Test Method 435, to assist laboratories, consultants, local air pollution control districts, and other asbestos stakeholders in the application and performance of M435. 

Test Method 435 (M435) (Cal. Code Regs., tit. 17,  94147), entitled "Determination of Asbestos Content of Serpentine Aggregate," was recommended for adoption during hearings of the Air Resources Board (ARB or Board) in April 1990, in support of the Asbestos Airborne Toxic Control Measure (ATCM) for Surfacing Applications (Cal. Code Regs., tit. 17, 39106).  This ATCM aims to reduce public exposure to naturally occurring asbestos (NOA) by limiting the asbestos content of surfacing materials.  In 2001, the Board also recommended for adoption the Asbestos ATCM for Construction, Grading, Quarrying, and Surface Mining Operations (Cal. Code Regs., tit. 17, 39105) to minimize generating asbestos-containing dust during those activities.  This second ATCM also references M435 as an approved test to measure the asbestos content of bulk materials. 

In response to stakeholders who were receiving variable M435 results from analyses of the same samples by different laboratories, ARB staff conducted a M435 Interlaboratory Study (ILS).  The ILS identified variability in laboratory equipment and procedures that can significantly affect the reported asbestos content of M435 rock and soil samples.  Following this, all aspects of the test method were studied. 

This non-regulatory guidance document consists of clarifications and recommendations developed by ARB staff through years of method testing and iterative consultations with many asbestos stakeholders during public workshops, surveys, and presentations in scientific meetings.  It is expected that using the guidelines in this document during the collection, processing, and analysis of potential asbestos-containing aggregate samples will result in more accurate and repeatable M435 asbestos content measurements. 

Questions regarding this document can be sent via email to Rebecca Neumann at rebecca.neumann@arb.ca.gov or by mail to:

Air Resources Board
Monitoring and Laboratory Division
P.O. Box 2815, Sacramento, CA 95812
Attention: Rebecca Neumann



Test Method 435 Guidance Document and Appendixes - April 28, 2017


For previous M435 public workshops and meetings click on this link.



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For more information about the M435 revision activities, please contact Patrick Rainey at (916) 327-4756 or Rebecca Neumann at (916) 324-1145.

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