Re: Using microscope to test for asbestos fibers

From: Aaron (nghy_at_comcast.net)
Date: 07/19/04 

Date: 18 Jul 2004 19:28:15 -0500

I apologize for the many typographical errors. Here is a corrected
text.

Asbestos is a difficult subject for a microscopist even in a well
equipped laboratory.. I think you may have trouble with field studies
unless you can set up a suitable field laboratory.

The microscopes used for serious detection and analysis of asbestos
particles are compound microscopes outfitted for mineral studies using
polarized light microscopy and are called petrographic microscopes.
These have calibrated polarizer and analyzer filters, strain free
optical components (objectives, condenser, eyepieces, etc.), a 360
degree rotating stage with angular scale and provisions for inserting
retardation plates/filters in the optical path. The entire optical
path can be specially aligned so the specimen can be observed while
centered in the field as the stage is rotated. The color changes and
angles of rotation observed while running the test procedures with a
polarized light microscope constitute a defining physical property of
the mineral being observed.

The particular objective magnifications are chosen according the size
of the particles you want to trace. Since asbestos can be broken down
into very small particles, their size may require use of a 100X oil
pol objectivs. Larger particles would not require the same high
magnificartions.

In addition to an adequate polarized light microscope, a microscopist
needs training and experience to become competent in identifying
asbestos particles. Asbestos, which occurs in several different
forms, superficially resembles other mineral fibers. In general, I
would recommend obtaining known standard samples and research the
literature for the standard test methods. Laboratory workers in the
USA who do this for a living have to go through a certification
process.. There is a whole infrastructure to support the asbestos
removal industry. There are suppliers that produce everything that is
needed along the way. .

Of course if you are a hobbyist the rigorous requirements can be
relaxed. But if your are doing serious acedemic work or interfacing
with a government agency, this area is very heavily researched and
regulated. See various OSHA materials.

Aaron

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