Assessment of potential asbestos exposures from jet engine overhaul work

Our plain-English summary of Assessment of potential asbestos exposures from jet engine overhaul work, by S.P. Mlynarek, D.R. Van Orden (Regulatory Toxicology and Pharmacology, 2012).

The study

• Authors: S.P. Mlynarek, D.R. Van Orden
• Journal: Regulatory Toxicology and Pharmacology
• Published: 2012;63(1):78-83
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Asbestos fibers have been used in a wide variety of products and numerous studies have shown that exposures from the use or manipulation of these products can vary widely. Jet engines contained various components (gaskets, clamps, o-rings and insulation) that contained asbestos that potentially could release airborne fibers during routine maintenance or during an engine overhaul. To evaluate the potential exposures to aircraft mechanics, a Pratt & Whitney JT3D jet engine was obtained and overhauled by experienced mechanics using tools and work practices similar to those used since the time this engine was manufactured. This study has demonstrated that the disturbance of asbestos-containing gaskets, o-rings, and other types of asbestos-containing components, while performing overhaul work to a jet engine produces very few airborne fibers, and that virtually none of these aerosolized fibers is asbestos. The overhaul work was observed to be dirty and oily. The exposures to the mechanics and bystanders were several orders of magnitude below OSHA exposure regulations, both current and historic. The data presented underscore the lack of risk to the health of persons conducting this work and to other persons in proximity to it from airborne asbestos.

Copyright © 2012 Elsevier Inc. All rights reserved.

In plain English

This study measured airborne asbestos released when experienced mechanics overhauled a jet engine. Over three weeks at a Miami, Florida repair facility, mechanics took apart and rebuilt a Pratt & Whitney JT3D-7 jet engine built in 1968. They followed the engine manuals and used tools similar to those used since the engine was made. Of 403 samples of Pratt & Whitney engine parts, 37 (9%) contained asbestos, in every case chrysotile. Air samples worn by workers were counted under a light microscope, which counts all fibers, not only asbestos. They averaged 0.010 fibers per milliliter during disassembly and 0.008 during assembly. A bystander's samples averaged 0.013 and 0.014. These were task-length samples, not 8-hour averages. Electron microscopy found no asbestos fibers in any of the 111 personal samples analyzed and found chrysotile in 2 of 138 indoor area samples. The authors noted the work was oily and that oil and fluids may have suppressed fiber release. The authors concluded that workers' personal asbestos exposure was at or below background ambient levels. Pratt & Whitney funded the study, and the authors disclosed involvement in asbestos litigation.

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: Exposure simulation study: one jet engine was overhauled under observation, with personal, bystander, indoor area and outdoor air sampling and bulk sampling of parts
• Who was studied: One Pratt & Whitney JT3D-7 engine (built 1968, in service until 1986). It was overhauled over three weeks at JB Power LTD, an FAA-certified repair station in Miami, Florida, by mechanics with 7 to 36 years of experience. The number of mechanics and the study dates are not given. Samples were also taken on one bystander.
• Exposure: Disassembly and reassembly of a jet engine, including removal and installation of gaskets, o-rings, seals and insulated clamps. Asbestos found in the parts was chrysotile, at 30% to 90% in the positive Pratt & Whitney parts.
• Main results:
  • Of 403 bulk samples of Pratt & Whitney engine parts, 37 (9%) contained asbestos, all chrysotile
  • 5 of 17 samples of Quick Engine Change (QEC) parts, which are not Pratt & Whitney products, contained asbestos, all chrysotile. The article prints this as 33%.
  • Worker personal samples by light microscopy (PCM, counting all fibers) had a mean of 0.010 f/ml during disassembly and 0.008 f/ml during assembly
  • Bystander samples by PCM averaged 0.013 f/ml during disassembly and 0.014 f/ml during assembly
  • The highest single sample was 0.050 f/ml (PCM), a bystander sample during assembly
  • Electron microscopy (TEM) found no asbestos in any of the 111 personal samples analyzed. Asbestos was found in 2 of the 138 indoor area samples.
  • 78 of the duplicate personal air samples were archived and not analyzed
  • Area samples near the work averaged 0.003 f/ml by PCM during both disassembly and assembly
  • Both asbestos-positive area samples (1.4% of 138) were collected during assembly
  • On reanalysis by ISO 10312, one positive area sample had two chrysotile fibers shorter than 5 micrometres, and the other had one chrysotile fiber longer than 5 micrometres
  • Average asbestos fiber concentration for all indoor area samples (PCME) was approximately 0.000005 asbestos f/ml
  • Worker PCM fiber levels were marginally higher during disassembly than during assembly (p = 0.0626)
  • Gaskets and seals were removed by hand or with a screwdriver. No powered grinders or wire brushes were used.
• The authors' conclusion: The authors concluded that the personal airborne asbestos exposure of workers overhauling jet engines was at or below background ambient levels
• Limitations the authors state:
  • The authors noted that oil and fluids on the engine parts may have suppressed the release of airborne fibers
  • Air concentrations are task-based, not 8-hour time-weighted averages
  • Some time-consuming steps of a normal overhaul were not performed; the authors state these involve no asbestos-containing parts
  • Air changes per hour in the building were not measured
  • Funding disclosure (stated by the authors, not framed as a limitation): the study was supported by Pratt & Whitney, and the authors have participated in asbestos product litigation

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Gasket, OSHA.

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