Testing for Asbestos 4

[dik]

Does anyone know how testing labs test for asbestos? Is it a matter of 'dissolving' the other material and looking for asbestos strands/particulate under a microscope? Possibly thin sections under a petrographic microscope? or some other way... I was curious what testing labs do...

Dik

 

[CANPRO]

I glanced over this link quick enough to see they count fibers with a microscope...seems like it answers your question.

https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=standards&p_id=9997

 

[bridgebuster]

We sub this work out. They use Polarized Light Microscopy. Transmission Electron Microscopy is used if the PLM reults are non-conclusive or negative, such as a non-friable organically bound material.

 

[Ron]

As BB says, initial screening is done with PLM on stained specimen. TEM is used for follow-up.

Sampling is reasonably important, as is knowing which materials to suspect...such as 9"x9" composite floor tile as compared to 12"x12" floor tile. Most of the 9" tile contains asbestos, while some of the 12" tile contains it. Neither is generally friable so cleanup is a bit easier. Many wall and ceiling plasters (lime or gypsum based plasters) contained asbestos. These are usually friable.

Asphalt based adhesives for floor tile usually contained asbestos fillers. Asphalt flashing cement produced before about 1995 contains asbestos as a filler. Many roofing felts, both general felts and flashing felts produced before about 1990 contained asbestos. Many pipe insulations contained asbestos and "popcorn" ceilings popular in the 60's, 70's, and 80's contained asbestos. Almost any vermiculite was contaminated with asbestos fibers.

Outside the production of asbestos containing materials (ACM), I don't know that there has ever been a documented health issue with incidental exposure to ACM. It was a big scare for public buildings, particularly schools in the 1980's and 1990's.

 

[TomDOT]

Just as an FYI,the "quick" PLM is not very precise. If you get a PLM result in the single-digit range, it is probably worth requiring a retest by point count. I have frequently seen the quickie PLM come back with 2-3%, then the same samples below 1% with an actual point count.

1% is the critical number in the USA (unless there is a more restrictive local regulation)

The vermiculite problem largely stems from the Libby, Montana mine - a very prolific producer until they shut down. It probably produced around 80% of the world's vermiculite from sometime in the 1920s until 1990 when it was shut down.

Older talc is often contaminated with asbestos as well - there were some talc mines in California contaminated with asbestos.

 

[dik]

Thanks gentlemen... thought it might be with a petrographic microscope using polarised light, but wasn't sure. Wasn't aware they used TEM or Phase Limiting Microscope. I was just curious... we usually ship samples away and had a recent project with negative response...

Thanks

Dik

 

[TomDOT]

I'm pretty sure sampling requires a specialized certification - we sub out sampling and testing.