The second part of the presentation was significantly more complicated than the first part. This does not mean the first part was not valuable, we are trying to indicate the second part really got into some of the details of analyzing the minerals utilizing polarized light microscopes, the quantitation of the samples, and additional methods of analysis including advantages and disadvantages (enough big words for everyone).
The second presentation started
with a discussion of the new NYS DOH Guidance letter regarding the analysis of
vermiculite containing materials (VCM).
We discussed this issue in our Blog on 7/21/13. The big issue is the
disclaimer being placed on the results and what is the best course of action
for results that indicate greater than 10% vermiculite and less than or equal
to 1% asbestos with the disclaimer.
To understand the problems with
analysis Mr. Cahill’s presentation showed us that vermiculite comes in three
types – large (light), medium, & fine (dark). See
figure below:
As you can see the
material is varying levels of “chunkiness”. According to EMSL, when picking through the sample rice grain sized asbestos chunks can
sometimes be detected visually. However,
the absence of these chunks does not mean the sample is asbestos free. The polarized light microscope (PLM) methodology is strong for identification, while quantification is weak. The PLM analysis is only as good as the prep
(especially for point counting). The sample
must be uniform, random, & a monolayer (the height of a particle size prevents a
nice monolayer). Based on this
information the problems regarding vermiculite analysis are:
- Particle size
prohibits making a proper slide mount.
- Asbestos not
always homogeneous within the sample
- Asbestos can
be locked between plates & therefore not easily detected
- Non-regulated
Libby Amphiboles are present.
The discussion then turned to
other methods of analysis, noting that monokote fireproofing has removable
matrix. Methods with matrix removal
include:
·
EPA (600) PLM NOB
·
EPA (600) TEM NOB
·
NYS ELAP 198.6 (PLM)
·
NYS ELAP 198.4 (TEM)
·
Chatfield SOP (TEM)
At this point, the preferred NYS
ELAP method is 198.6, but that means you get the disclaimer on your
results. EMSL’s presentation discussed 4
different approaches of what to do regarding VCM, these approaches are:
- Cancel or
delay asbestos surveys if possible until final regulations are in place.
- If initial
analysis determines vermiculite content >10% they are stopping. The material is treated as ACM.
- If 198.1
analysis determines vermiculite content >10% proceed to 198.6 to
determine the asbestos percentage.
Materials are classified as ACM or non-ACM accordingly, disclaimer
is tolerated.
- Approach 2 or
3 are followed for regulatory compliance and then various additional prep
and analysis steps are requested.
Transmission Electron Microscopy (TEM) analysis is typically a part
of this process to demonstrate “Best Available Technology”.
Options available for Approach 4
are:
- Cincinnati
Method – vermiculite separated into fractions, floating, sinks, &
suspended fractions. Analysis is by
a combination PLM/TEM
- CARB (CA Air
Resource Board) 435 Method – Sample is milled, followed by a PLM point
count
- EPA 600
Milling followed by PLM/EPA 600 Milling followed by TEM analysis – Can
break out of mass percent with & without the contribution of Libby
amphiboles
- ASTM TEM
Qualitative Method – excellent fiber ID but no quantification
- Addison Davies
Method – remove vermiculite prior analysis
We learned a lot in this seminar
regarding different methodologies and the problems involved with analyzing
vermiculite and VCM. It will be
interesting moving forward to see which direction the analysis of these
materials goes. Based on the
presentation, the EPA 600 milling followed by TEM analysis sounds interesting
and promising. However, NYS ELAP or EPA
will be making that decision and only time will tell.
