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Showing posts with label Phase Contrast Micorscopy. Show all posts
Showing posts with label Phase Contrast Micorscopy. Show all posts

Monday, October 24, 2022

The Reality of Asbestos Clearance Air Sampling! Are You Sampling Enough?

We attended the Environmental Information Association (EIA) 2022 National Conference and Exhibition in Phoenix, Arizona from March 20, through March 23, 2022.  We attended several sessions regarding asbestos where we discussed with some attendees asbestos clearance air sampling and what are the Federal requirements.  Based on those discussions we figured it was time to write an article on this topic.  To make sure we wrote this article based on general industry practice, versus what we are used to in New York State and New York City, we consulted with Mr. Tom Laubenthal, of TGL Consulting, Inc., and Mr. Dana Brown, of Time's Dark Captains.  Since everything else seems to start with the Environmental Protection Agency's (EPA's) Asbestos-Containing Materials in Schools Rule (40 CFR Part 763, Subpart E, known in the industry as the Asbestos Hazard Emergency Response Act (AHERA)) why don't we start there?  The AHERA regulation remember applies to schools from Kindergarten to 12th grade (K-12), both public and private schools.  The requirements are found in two sections of the rule:

  • Response Actions; §763.90 (i)
  • Appendix A (to Subpart E) - Interim Transmission Electron Microscopy Analytical Methods - Mandatory and NonMandatory - and Mandatory Section to Determine Completion of Response Actions

For all intents and purposes, these methods serve as the industry standard when final clearance is performed for most asbestos abatement projects, especially when areas are to be re-occupied. We’ll discuss applicability issues as we go. 

TEM Analysis

First, let's discuss the requirement for aggressive clearance sampling.  In the AHERA regulation, aggressive sampling means floors, ceilings, and walls shall be swept with the exhaust of a minimum one (1) horsepower leaf blower.  Some states and specifications may also require the use of fans as described in the non-mandatory section of Appendix A.  The non-mandatory section states, that stationary fans shall be placed in locations that will not interfere with the air monitoring equipment.  Fan air is directed toward the ceiling.  One fan shall be used for every 10,000 cubic feet (CF) of a worksite.  This is required in the New York State Department of Labor's Asbestos Regulation Industrial Code Rule 56 (NYSDOL ICR56) and the New York City Department of Environmental Protection Asbestos Regulation Title 15 (NYCDEP Title 15).  However, NYSDOL ICR56 also requires one fan per room in addition to the one fan per 10,000 CF.

This is not in the spirit of the AHERA/NYSDOL ICR56/NYCDEP Title 15 requirements for aggressive clearance sampling. Thank you Greg Mance for the photo.

As defined by the AHERA rules, final clearance air sampling can be done by phase contrast microscopy (PCM) methodology for projects less than or equal to 160 square feet (SF) or 260 linear feet (LF) by the National Institute for Occupational Safety and Health (NIOSH) 7400 methodology (Issue 3: 14 June 2019 is the current issue).  For projects greater than 160 SF or 260 LF clearance shall be done by the AHERA transmission electron microscopy (TEM) method (requirements at 763.90 (i) (4) and Appendix A).

Graphic courtesy Tom Laubenthal

There are some similarities between the AHERA TEM and NIOSH 7400 methods.  For example, the AHERA TEM method (Appendix A) allows for the use of either a 25-millimeter (mm) filter cassette or a 37-mm filter cassette.  We haven't used a 37-mm cassette since the industry switched from the old asbestos sampling method NIOSH P&CAM 239 to the NIOSH 7400 method that was formally adopted into AHERA.  For sampling, whether it is the AHERA TEM method or the NIOSH 7400 method, we use a 25-mm 3-piece cassette with 50-mm electrically conductive extension cowl cassettes.  The two methods require the filter cassette to face 45 degrees downward from the horizontal.  The filter material used is mixed cellulose ester (MCE).  AHERA TEM method does allow for the use of polycarbonate (PC) filters as well.  The PC filters fell out of favor because post-sampling handling was more problematic than the MCE filters.  With PC filters, if samples sent to the lab are not handled carefully, the sampled fibers can move significantly from the filter surface.  This was widely discussed in the industry in the 1980s.  Since then, only MCE filters are used outside of specialty applications. 

The filter cassette is to face 45 degrees downward from the horizontal.

Both methods require blanks, however, that is where the similarities end.  The AHERA TEM method requires three blanks two field blanks and one laboratory (sealed) blank.  While the NIOSH 7400 method requires a minimum of two blanks or 10% of samples collected with a maximum of 10 blanks.  How the blanks are handled is different as well. The AHERA TEM method laboratory (sealed) blank is not opened and kept sealed, while the field blanks are opened for 30 seconds at the entrance to each abatement area and one at an ambient area.  While the NIOSH 7400 method requires the blanks to be opened at the same time as the other cassettes just prior to sampling and stored with the top covers of the cassettes that are running and remain open for the duration of sampling (here is an interesting difference, in some places the cassettes are stored in the box with the lid closed or, the way we were taught, they are placed in a Ziploc bag that is used to deliver the samples to the laboratory).  

A typical box of air sampling cassettes

Another difference is that with the AHERA TEM method we use a 0.45-micron (µm) MCE filter and the NIOSH 7400 method uses a 0.8 µm MCE filter.  This refers to the size of the air passages in the filter material. Filter manufacturers will color code or mark the label so that the type of filter within the cassette assembly is known to the user and the laboratory.

TEM filter is 0.45-micron.  PCM filter is 0.8-micron.

Let's get to some of the interesting items such as how the samples are taken and how many are required.  The AHERA TEM method is straightforward, it requires 5 samples inside the work area and 5 samples outside the work area that represent air entering the abatement site plus the blanks (as mentioned above) for a total of 13 samples.  These samples should run from 1 to less than 10 liters per minute (LPM) for a total volume of air greater than 1199 liters or greater (see Table 1 below for the recommended sampling volume range for this method, typically the volume range is between 1200 liters and 1800 liters).  It is interesting that the maximum flow rate is less than 10 LPM.  It would be interesting to find out how many in the industry actually sample at less than 10 LPM (i.e., 9.9 LPM versus 10 LPM).  Likely most of the industry merely samples at 10 LPM.  The statistical difference between 10 and 9.9 LPM, some regulators insist upon, is statistically insignificant and will affect method performance in no discernable manner.  Either way, this means your clearance samples will take a little over 2 hours to collect.  

In speaking with Mr. Tom Laubenthal, we learned at the time this method was developed it became known through the research involved that flow rates higher than 10 LPM could cause fibers to impact the MCE filters vertically and not horizontally to the filter surface.  This makes the sample analysis, counting, and identification, difficult and likely biased.  This is also the reason the method specifies a second MCE filter under the 0.45 µm sampling filter and the 5 µm diffuser. This additional filter is placed in this manner to attempt to create an even flow across the filter surface so that fibers impact the filter uniformly.  Since the fibers are lying flat on the filter this is the reason for turning the sample upright before interrupting the pump flow to ensure the fibers remain on the filter.

Sampling Cassette Configuration

In the AHERA TEM method, the clearance samples pass when the average concentration of the five samples inside the work area does not exceed 70 structures per square millimeter (s/mm2).  See AHERA at 763.90 (i) (3) for an optional clearance test based on the z-test which compares the outside and inside air samples.  This is rarely necessary.  But cases have occurred when contamination can exist in the air outside the work area that could cause a failure in the work area.

This TEM asbestos image is from the Centers for Disease Control (CDC) "Asbestos Fibers and Other Elongate Mineral Particles: State of the Science and Roadmap for Research"

The NIOSH 7400 method for final clearance is also interesting when it comes to how the sample is taken and how many are based on the project.  For schools, when PCM is allowed, it's 5 samples inside the work area.  What's interesting is that the clearance is based on each sample and each sample must be less than or equal to a limit of quantitation (LOQ) for PCM of 0.01 fibers per cubic centimeter (f/cc).  Well according to the NIOSH 7400 method how do you achieve clearance at that LOQ?  This concept of LOQ is not a concept understood by many that use the NIOSH 7400 method for all its purposes.  In the NIOSH 7400 method, this issue is addressed as follows in the section "Sampling", number 4 on page 4.  It utilizes the formula below to determine the amount of time needed to achieve the fiber density, E, for optimum filter loading.  So, the minimum density the method allows is 100 fibers per square millimete(mm2).  The Ac is the collection area for a 25-mm cassette which is 385 mm2.  The Q is the sampling flow rate in LPM, so let's say that is 16 (the maximum flow rate allowed by the method).  The L is the concentration of fibers in the air, we are looking to achieve clearance at 0.01 fibers/cubic centimeters (f/cc).  So if you plug these numbers into the formula you get a time of 240.6 minutes, which means the sample would have to run for a little over 4 hours at 16 liters per minute (total volume of air of 3,850 liters).

Realize that is running the sample at 16 LPM.  If your pump/flowmeter can only go to 15 LPM then you would have to run the sample for 256.7 minutes which is just short of 4 hours and 15 minutes.  The lower the flow rate, the longer time it will take to meet sample volume requirements. 

Airbox High-Performance Air Sampler

Many believe or have been misled to believe that PCM sampling is the same as TEM sampling in terms of sampling volume.  This is not the case.  A PCM sample volume meeting AHERA clearance requirements are not at 1200 liters.  To do so is outside of the NIOSH 7400 method requirements for this purpose.  In the NIOSH 7400 method, the issue regarding "relatively clean" environments" is addressed on page 4, number 4, note number 1 which states  "In relatively clean atmospheres, where targeted fiber concentrations are much less than 0.1 f/cc, use larger sample volumes (3000 to 10,000 liters) to achieve quantifiable loadings."  Even though the formula calculates that 3,850 liters of air should be collected, many people use note 1 to collect 3,000 liters of air for clearance.  Either way clearance samples should be collected using no less than 3,000 liters of air as the minimum allowed for the NIOSH 7400 method requirements and AHERA compliance. 

PCM image of fibers

The true problem is the NIOSH 7400 was never designed as a clearance tool, it was designed as a personal air sampling method.  NIOSH and the Occupational Health and Safety Administration (OSHA) still view the method in that manner officially.  The other problem with PCM is that all fibers meeting method criteria are counted, not just asbestos fibers.  The AHERA TEM method is the only procedure that was designed as a final clearance air sampling method. Only asbestos fibers/structures are counted in the analysis meeting method criteria for size, and those much smaller than can be determined by the PCM.

 

EPA's Silver Book

Realize this is not something out of the ordinary the EPA's publication "Measuring Airborne Asbestos Following An Abatement Action" (otherwise known as the Silver Book) written in November 1985 on page 2-6 recommends the sample volume for the PCM analysis should be a minimum of 3,000 liters of air (though at the time of this publication it was describing the NIOSH P&CAM 239 PCM methodology).  In addition, in March 2015 the EIA published a revision to the EPA's 1985 document "Guidance for Controlling Asbestos-Containing Materials in Buildings"(EPA 560/5-85-024, known as the Purple Book).  This nationally peer-reviewed document was re-titled "Managing Asbestos in Buildings: A Guide for Owners and Managers."  Chapter 5 (on page 88) says the minimum sampling volume of 3,000 liters of air for samples taken to meet the NIOSH 7400 method requirements for LOQ sampling.  Mr. Dana Brown did a video regarding the LOQ issue and why NIOSH 7400 method is not the best choice for clearance, you can see it below. 

This doesn't count that we have called for the AHERA TEM method to be utilized for asbestos-containing floor tiles and mastic removals based on our previous blog post "Asbestos Floor Tile Debate", published in the August 2017 issue of Healthy Indoors Magazine, which found that the NIOSH 7400 method is not able to analyze the type of fibers (Grade 7-Shorts and Floats that are known to be less than 5 microns) found in these materials because of the known small fiber sizes generated by floor tile work.  Whether AHERA-based work or asbestos abatement where re-occupancy will occur, the surest way to make sure an area is ready to be given back to the public to be free of asbestos as practicable by current methods, and the fastest method for clearance would be the AHERA TEM method.  

NYSDOL ICR56 Definition of an Asbestos Project

Of course, those of you who work in New York State or New York City realize these requirements only apply to public and private K-12 schools.  So they don't apply to other buildings, or do they?  First, let's take the NYSDOL ICR56 Subpart 56-4, page 35 is the air sampling requirements.  56-4.6 "Test Methods" on page 36 says "the same NIOSH approved methodology for project air sampling and for analysis of the air samples shall be used at all phases of an asbestos project that require area air sampling and analysis, with the possible exception of clearance air sampling."  This means that the NIOSH 7400 method must be followed for all phases except clearance (Phase IIC of the asbestos project) this allows you to use either the NIOSH 7400 method or the AHERA TEM method instead for clearance.  So this means you have to follow the NIOSH 7400 method's LOQ requirements for all phases (Phase I B and Phase II A, B, & C) of the asbestos project.  In addition, the NYSDOL ICR56 regulation for clearance is less than 0.01 f/cc so that changes the formula again.  Let's use 0.009 f/cc for the L instead and still use 16 liters per minute, well that means the sample has to run for 267 minutes, almost 4 hours, and 30 minutes (a total volume of air of 4,278 liters).

The consummate leader cultivates the moral law, and strictly adheres to method and discipline; thus it is in his power to control success. ~ Sun Tzu


So why does everyone sample 1,200 liters of air for all samples?  On April 8, 2011, the New York State Department of Health (NYSDOH) Wadsworth Center issued frequently asked questions (FAQs) regarding asbestos/fibers analysis that were developed through the collaboration of the NYSDOH Environmental Laboratory Approval Program (ELAP) and the Bureau of Occupational Health and the NYSDOL.  In this FAQ is FAQ#13: What is the minimum sampling volume to be collected for air sampling associated with (a) post-abatement (clearance) air monitoring and (b) post-abatement area monitoring for PCM analysis?  The answer that was given was:  Within the upcoming revision to NYS Industrial Code Rule 56, minimum air sample volume requirements 
are being added for both background and clearance PCM air samples. The minimum volume will be 1,200 liters for all background and clearance PCM air samples collected.  Hopefully, you all see the problem here...the code rule has not been revised to include this requirement, and even if it did change this is a minimum volume of air and does not comply with the NIOSH 7400 method requirement.

Buy our Asbestos Air Sampling Chart here.
Read about our Asbestos Air Sampling Charts here.

Next up is the NYCDEP Title 15NYCDEP Title 15 was just updated on May 28th, 2022.  See our blog post "New York City's Asbestos Regulation Revised, Again!" for more information on the changes.  However, these changes did not make any significant changes to what we are discussing.  Under Subpart D, 1-37 (b) "Area air sampling equipment for PCM shall be utilized in accordance with the sampling procedures specified within the NIOSH 7400 Method modified for area sampling."  Again, it means you must follow the LOQ requirements in the NIOSH 7400 method, even though NYCDEP Title 15 does give you minimum sample volumes.  For clearance by NIOSH 7400 method, it's 1800 liters and for the AHERA TEM method, it's 1250 liters.  Remember these are minimums.  In addition, NYCDEP Title 15 limits the flow rate to a maximum of 15 liters per minute.  This means to achieve the LOQ requirement it would take 256.7 minutes which is just short of 4 hours and 15 minutes (total volume of air of 3,850 liters).  The NYCDEP Title 15 minimum volume would not meet the LOQ requirements in the NIOSH 7400 method.  We hope this post has helped to resolve those pesky questions regarding clearance and convince you that probably the best air sampling method for clearance is the AHERA TEM method! 


Tuesday, July 11, 2017

Asbestos Floor Tile Debate Results

… … This debate regarding asbestos floor tiles started at the Professional Abatement Contractors of New York's (PACNY's) 2017 Environmental Conference.  At the conference, after our presentation, a member of the audience challenged our statement that asbestos floor tile removal should be cleared by the Asbestos Hazard Emergency Response Act (AHERA) Transmission Electron Microscope (TEM) method (see the video of our presentation here, the challenge is at the end of the video).  In the video Mr. Chris Alonge, of Dormitory Authority of the State of New York (DASNY) defends our call for TEM clearance for asbestos floor tiles and we had some additional people approach us after the presentation supporting our side of the debate.  As some of you know, we decided it would be neat to see if their are others who feel the same way.  We decided to use Survey Monkey to ask three simple questions regarding this issue.  These questions were:
  • When doing asbestos flooring removal, which method was used the National Institute of Occupational Safety and Health (NIOSH) 7400 Phase Contrast Microscope (PCM) method or AHERA TEM method for clearance? The answers we got was 47.1% used the NIOSH 7400 method; while 29.4% used both methods; and 23.5% only used the TEM method.
  • When using the AHERA method for clearance, what was the typical size of the fibers found?  The answers we got were 58.8% less than 5 micron; 29.4% both sizes were equal amounts; and 11.8% greater than 5 micron.
  • Have you ever encountered during asbestos flooring removal when utilizing both the NIOSH 7400 (PCM) & the AHERA (TEM) methods of analyses, that the NIOSH 7400 passed while the AHERA method failed?  The answers we got were 52.6% yes, 36.8% no, and 10.5 never used both.
Improperly Removed Floor Tiles
We would like to thank all of you who participated in our survey.  The results are interesting, the first question is not surprising since the NIOSH 7400 method is the cheapest method and both New York State (NYS) and New York City (NYC) require this method as the minimum method.  The second question is also not surprising since this is the reason for our call for clearance for floor tile jobs to be by the AHERA TEM method.  The final question proves the point we've been making.  If even one project can actually fail by AHERA TEM but pass using the NIOSH 7400, this should be a concern for any person who is concerned for the safety and health of the occupants who would occupy the space after clearance.
Another Improper Floor Tile Removal
As we mentioned in our presentation, we didn't come up with this idea out of the blue.  In 2003, Applied Occupational and Environmental Hygiene published a study called "Asbestos Release During Removal of Resilient Floor Covering Materials by Recommended Work Practices of the Resilient Floor Covering Institute" by Marion Glenn Williams, Jr. and Robert N. Crossman, Jr. from the University of Texas Health Center at Tyler, Tyler Texas.  You can find the study in our Future Environment Designs website under our Resource Page in the dropbox folder.

Some of the major points from this study were:
  • Asbestos used in flooring materials is Grade 7 - Shorts and Floats.  The dimensions of this material are very small and may not be resolvable by the Polarized Light Microscope (PLM).  Which is why in NYS we require floor tiles to be analyzed as a nonfriable organically bound (NOB) material (analysis by PLM and if negative result for asbestos then analysis by TEM).
  • Since the dimensions of these fibers used in the manufacture of floor tiles are so small, it would explain why we typically see very low personal exposure levels by phase contrast microscope (PCM) during floor tile removals.  Many ultrafine fibers are not counted due to resolution (0.2-0.25 um) and the count protocol, which provides that only fibers longer than 5 micron with a 3:1 or greater length-to-width ratio are counted.
  • Many research studies have found the preponderance of fibers at autopsy left in lung tissue, pleural plaques, and lymph nodes of persons who have occupational exposure to asbestos are shorter them 5 micron in length.
  • The NIOSH 7402 TEM method is flawed because it underreports the amount of asbestos in the samples because it ignores all fibers less than or equal to 5 micron and all those fibers longer than 5 micron but less than 0.25 micron in diameter.
  • AHERA TEM method counts for total asbestos structures per cubic centimeter averaged 22 times greater than the PCM fiber counts on the same filters.
  • AHERA TEM asbestos concentrations obtained during mastic removal with a commercial mastic remover averaged 11 times higher than those measured when removal used amended water.
  • The study also found that there was considerable amounts of asbestos dust settled on exposed surfaces during tile removal.  Indicating a need to thoroughly HEPA vacuum and wet clean surfaces or dust may remain that could be re-entrained by occupant activity.
  • The study also indicates that workers in these areas, would not have to wear respirators, so anyone in these areas would have inhaled asbestos fibers or structures of respirable dimensions.
  • The study suggests that for Resilient Flooring Removal clearance sampling should use aggressive methods, require a clearance level of less than 0.005 structures per cubic centimeter for each sample, and all samples analyzed by AHERA TEM protocol.  It also suggests a minimum number of samples for clearance should be one sample per 500 square feet, a volume of air of at least 1250 liters, and the use of 0.45 micron mixed cellulose ester filters in a 25 millimeter diameter conducting cassette with a 50 millimeter extension cowl.
As we said, we did not arrive at our decision lightly.  After reading this study it became apparent to us that asbestos containing flooring or mastic removal should be cleared using the AHERA TEM method to ensure the work area is actually free of asbestos fibers (we already do this in schools under AHERA for large asbestos projects, some schools require all asbestos projects ave to be cleared by AHERA TEM).  In addition, any negative exposure assessment for floor tile removal that does not include AHERA TEM analysis of some of the samples should not be accepted as definitive to allow workers to not use respirators during asbestos flooring removal.  As the study showed their could be significant exposure to workers from these respirable fibers/structures that the NIOSH 7400 method is not picking up.

We hope this information explains our position, and we look forward to a continuation of this debate. We intend to press the case for a requirement for AHERA TEM clearance for flooring removal, especially if New York State truly intends to move forward with an update of Industrial Code Rule 56.
  
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