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EMSL Adopts New NIOSH 7400 PCM Method

Category Press Release
Publish Date 6/13/2019
Author Lacey Wallen
Title EMSL Adopts New NIOSH 7400 PCM Method
Introduction A new version of the widely used Phase Contrast Microscopy (PCM) Method Asbestos and Other Fibers by PCM 7400 has been released and EMSL has adopted its changes.

Cinnaminson, NJ,  June 13th , 2019

The National Institute of Occupational Safety and Health (NIOSH), an agency that is part of the Center for Disease Control (CDC), recently released a new version of the widely used Phase Contrast Microscopy (PCM) Method Asbestos and Other Fibers by PCM 7400. The update is dated April 29, 2019 and is effective immediately. The new method can be found here: NIOSH Manual of Analytical Methods.

There are many changes to the method, some big and some small.  In all, the changes doubled the size of the method from 15 pages to 40. Most of the larger changes are either optional or informative references. However, there are also many additional minor changes that alter past suggestions (“should”) to mandatory requirements (“shall”).

Some of the NIOSH 7400 Method’s requirements:
  • Calibrate not just the scope, but each scope and analyst combination.
  • A Quality Assurance officer shall maintain control of a set of standard reference slides that he/she will supply to the analyst blindly at least once per day. From these reference slide analyses, the laboratory must determine inter-analyst and intra-analyst precision reported as relative standard deviation (Sr). This must be done for three ranges and control charts must be created and maintained for each.
  • All laboratories shall participate in a proficiency testing program such as the AIHA Proficiency Analytical Testing (PAT) program.
  • Each laboratory shall participate in a round robin program that includes at least two other laboratories.

Some of the more substantial changes:

  • An alternative clearing procedure using DMF (Dimethylformamide) and acetic acid rather than the traditional acetone procedure. This technique eliminates the chance of undissolved residues that can be mistakenly counted as fibers as with the old acetone prep technique.
  • Euparil as an alternative mounting medium instead of the more traditional Triacetin. Euparal dries to a solid thus locking fibers in place creating a permanent mount. Fiber migration can occur with the traditional Triacetin mounts over long periods of time.
  • Removal of reference to the HSE/NPL test slide which is no longer available. A new more generic description of the phase shift test slides allows laboratories to be compliant with method requirements.
  • Introduction of specialized coverslips with relocatable fields for use in training.

“It’s very interesting to see the changes that were made to PCM 7400,” said Ed Cahill, Vice President of EMSL Analytical, Inc.’s Asbestos Division. “We have 40 laboratories that use PCM for asbestos testing across the United States and Canada so it is very important that we are compliant with this new version.”

To ensure your laboratory is complaint with this new version and if you have any questions, please contact your local EMSL laboratory or Ed Cahill at, or 1-800-220-3675 extension 2565. To view a full list of EMSL’s locations that utilize PCM 7400, please visit

About EMSL Analytical, Inc.
EMSL Analytical is one of the leading testing laboratories with over 45 locations throughout the United States and Canada. EMSL is a nationally recognized and locally focused provider specializing in fast laboratory results for mold, bacteria, Legionella, USP <797>, pathogens, asbestos, lead, soot, char & ash from fires, VOC’s, odors, radon, formaldehyde, indoor air quality, microbiology, environmental, industrial hygiene, radiological, food, beverage & consumer products and material testing services for the identification of unknown substances. EMSL services both professionals and the general public. EMSL maintains an extensive list of accreditations from leading organizations as well as state and federal regulating bodies including, but not limited to A2LA, AIHA LAP, LLC. (AIHA EMLAP, AIHA IHLAP, AIHA ELLAP), NVLAP, CDC ELITE, CPSC, CA ELAP, NY ELAP, TX DOH, NJDEP and multiple other state accrediting agencies. Please visit our website at for a complete listing of accreditations. In addition, EMSL carries a wide range of Sampling Equipment and Investigative Products for environmental professionals.

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