Evaluation of airborne asbestos exposure from routine handling of asbestos-containing wire gauze pads in the research laboratory

Our plain-English summary of Evaluation of airborne asbestos exposure from routine handling of asbestos-containing wire gauze pads in the research laboratory, by E. Garcia, D. Newfang, J.P. Coyle, et al (Regulatory Toxicology and Pharmacology, 2018).

The study

• Authors: E. Garcia, D. Newfang, J.P. Coyle, C.L. Blake, J.W. Spencer, L.G. Burrelli, G.T. Johnson, R.D. Harbison
• Journal: Regulatory Toxicology and Pharmacology
• Published: 2018;96:135-141
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Three independently conducted asbestos exposure evaluations were conducted using wire gauze pads similar to standard practice in the laboratory setting. All testing occurred in a controlled atmosphere inside an enclosed chamber simulating a laboratory setting. Separate teams consisting of a laboratory technician, or technician and assistant simulated common tasks involving wire gauze pads, including heating and direct wire gauze manipulation. Area and personal air samples were collected and evaluated for asbestos consistent with the National Institute of Occupational Safety Health method 7400 and 7402, and the Asbestos Hazard Emergency Response Act (AHERA) method. Bulk gauze pad samples were analyzed by Polarized Light Microscopy and Transmission Electron Microscopy to determine asbestos content. Among air samples, chrysotile asbestos was the only fiber found in the first and third experiments, and tremolite asbestos for the second experiment. None of the air samples contained asbestos in concentrations above the current permissible regulatory levels promulgated by OSHA. These findings indicate that the level of asbestos exposure when working with wire gauze pads in the laboratory setting is much lower than levels associated with asbestosis or asbestos-related lung cancer and mesothelioma.

Copyright © 2018. Published by Elsevier Inc.

In plain English

This study measured airborne asbestos during simulated laboratory use of asbestos-containing wire gauze pads, which are placed over Bunsen burners to spread heat. The authors ran three scenarios. In the first, four new pads containing 75-85% chrysotile were heated, cooled and bent through six cycles in a chamber with low ventilation. In the second, two pads containing 5% tremolite were heated repeatedly without handling. In the third, one well-worn pad containing 15% chrysotile was heated and bent inside a glove box. In scenario 1, three of six area air samples contained chrysotile, with a highest estimate of 0.0017 fibers per cubic centimeter (f/cc). No asbestos was identified in the technician's or assistant's breathing-zone samples. In scenario 2, asbestos was found in one area sample (0.023 f/cc) and in none of the technician's breathing-zone samples. In scenario 3, no fibers were detected. The authors concluded that exposure was below OSHA limits. They noted that few pads were available and that the pads differed too much between scenarios for strong comparisons.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Simulated exposure assessment: three separately conducted test scenarios with different ventilation (about 1, 2 or more, and 10 air changes per hour), using area and personal breathing-zone air sampling plus bulk analysis of the pads
• Who was studied: No human population was followed. A laboratory technician (with an assistant in scenario 1) performed simulated tasks. Scenario 1 used five unused pads (four tested in air sampling) bought from The Perfect Parts Co., Baltimore, Maryland. Scenario 2 used two pads. Scenario 3 used one well-worn pad obtained from the University of South Florida campus.
• Exposure: Asbestos-containing wire gauze pads heated with Bunsen burners and manually bent or flexed. Before testing, scenario 1 pads contained 75-85% chrysotile, scenario 2 pads contained 5% tremolite, and the scenario 3 pad contained 15% chrysotile.
• Main results:
  • Scenario 1 area samples: three of six TEM-analyzed cassettes inside the chamber were positive for chrysotile.
  • Scenario 1 area samples: TEM-adjusted asbestos concentration estimates ranged from less than 0.0009 f/cc to 0.0017 f/cc.
  • Scenario 1 personal breathing-zone samples (technician and assistant): no asbestos fibers were identified by TEM in the 4-hour and 6-hour samples. The 30-minute samples were below the PCM detection limit and were not analyzed by TEM.
  • Scenario 2 area samples: of 12 samples taken during burn tests, five had detectable fibers by PCM. Asbestos was found only in the bench sample from the 120-minute burn, with a TEM-adjusted concentration of 0.023 f/cc.
  • Scenario 2 technician breathing-zone samples: the highest total fiber concentration by PCM was 0.054 f/cc (30-minute sample starting at 75 minutes). No asbestos fibers were identified by TEM.
  • Scenario 3 (one well-worn pad, simulated breathing-zone sampling in the glove box): fibers were below the PCM detection limit of 0.006 f/cc, and TEM identified no fibers.
  • Bulk analysis: the authors reported reductions in pad asbestos content after testing of 7.7% in chrysotile pads and 60% in tremolite pads (tremolite pads measured 5% before testing by PLM and 2% after testing by TEM). They stated that the extent of any heat breakdown was inconclusive.
• The authors' conclusion: The authors concluded that exposure to asbestos from wire gauze pad use in research laboratories was below the OSHA permissible exposure limit (0.1 f/cc, 8-hour) and excursion limit (1.0 f/cc, 30-minute). In their discussion they wrote that health risks are likely to be low or negligible.
• Limitations the authors state:
  • Sampling was limited by the small number of wire gauze pads available.
  • The scenario 2 pads contained a different asbestos type, so the tests were not alike and comparisons between them were kept to a minimum.
  • Taking bulk samples from the scenario 1 and 2 pads may have increased fiber shedding, which could have overestimated exposure compared with ordinary lab work.
  • Only one well-worn pad could be found, and its age and original asbestos content were unknown.
  • A longer simulated breathing-zone sampling period in scenario 3 would have been valuable.
  • Sampling or statistical errors were not characterized.
  • The counting method excludes short and thin fibers, so the worker could have been exposed to more asbestos than was detected.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, AHERA, Polarized Light Microscopy (PLM), Transmission Electron Microscopy (TEM), Chrysotile, Tremolite, OSHA, Lung Cancer.

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