Assessments of lung digestion methods for recovery of fibers

Our plain-English summary of Assessments of lung digestion methods for recovery of fibers, by D.B. Warheit, H.C. Hwang, L. Achinko (Environmental Research, 1991).

The study

• Authors: D.B. Warheit, H.C. Hwang, L. Achinko
• Journal: Environmental Research
• Published: 1991;54(2):183-93
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Evaluation of the pulmonary hazards associated with exposure to fibrous materials tends to be more complicated than assessments required for particulate materials. Fibers are defined by aspect ratios and it is generally considered that physical dimensions play an important role in the pathogenesis of fiber-related lung diseases. Several digestion techniques have been used to recover fibers from exposed lung tissue for clearance studies. Because many of the digestion fluids are corrosive (e.g., bleach, KOH), it is conceivable that the dimensions of recovered fibers are modified during the tissue digestion methods to assess whether the physical dimensions of bulk samples of fibers were altered following simulated digestion processing. Aliquots of crocidolite and chrysotile asbestos, Kevlar aramid, wollastonite, polyacrylonitrile (pan)-based carbon, and glass fibers were incubated with either saline, bleach, or KOH and then filtered. Scanning electron microscopy techniques were utilized to measure the physical dimensions (i.e., lengths and diameters) of at least 160 fibers per treatment group of each fiber type. Our results showed that the lengths and diameters of glass fibers and wollastonite were altered after treatment with KOH. In addition, treatment with bleach produced a small reduction in both asbestos fiber-type diameters, and greater changes in Kevlar and wollastonite diameters and carbon fiber lengths (P less than 0.05). These results indicate that lung digestion methods should be carefully assessed for each fiber type before initiating fiber clearance studies.

In plain English

This was a laboratory experiment; no people, animals or lung tissue were involved. The authors tested whether bleach and potassium hydroxide (KOH), caustic liquids used to dissolve lung tissue when recovering fibers for research, change the size of fibers. Samples of chrysotile and crocidolite asbestos, glass fibers, wollastonite, carbon fibers and Kevlar aramid were treated with saline (the comparison), bleach or KOH. At least 160 fibers per treatment group were then measured by scanning electron microscope. Bleach produced a small reduction in the diameters of both asbestos types. Chrysotile lengths were slightly reduced by bleach and KOH, while crocidolite lengths changed little. Other fibers changed more: KOH shortened glass fibers and increased their measured diameters, bleach or KOH raised the average diameter of wollastonite, and bleach thinned Kevlar and shortened carbon fibers. The authors noted that lung tissue, absent here, may protect fibers during real digestions. They concluded that lung digestion methods should be assessed for each fiber type before fiber clearance studies begin.

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: Laboratory (in vitro) experiment simulating lung-tissue digestion on bulk fiber samples, without any lung tissue; treated groups compared with saline-treated controls using Student's t test
• Who was studied: Bulk fiber samples (1 mg each, in triplicate): chrysotile asbestos from the Jeffrey Mine in Quebec, Canada; crocidolite asbestos from a UICC sample; code 100 glass fibers (Manville Corporation); NYAD G wollastonite (NYCO Corp.); polyacrylonitrile (pan)-based carbon fibers (Hercules Corp.); Kevlar aramid fibers (Du Pont Co.). At least 160 fibers measured per treatment group
• Exposure: After fixation, fibers were mixed with saline (0.85%), bleach (5.25% hypochlorite) or 11% KOH in ethanol and water, ground, and incubated at 60°C for 4 hours. They were then filtered and measured by scanning electron microscopy. Only particles with at least a 3:1 length-to-width ratio and at least 5 µm long were counted as fibers
• Main results:
  • Chrysotile asbestos: mean diameters of bleach-treated fibers were significantly reduced compared with saline- or KOH-treated fibers
  • Chrysotile asbestos: mean and median lengths of bleach- and KOH-treated fibers were slightly reduced compared with saline-treated fibers
  • Crocidolite asbestos: bleach or KOH had little effect on fiber lengths, but bleach-treated fibers showed a small decrease in diameter compared with KOH- or saline-treated fibers
  • Wollastonite: mean lengths were reduced and mean diameters substantially increased in bleach- and KOH-treated samples. Median diameters were 0.2 µm for both saline- and KOH-treated fibers and 0.4 µm for bleach-treated fibers
  • Glass fibers: KOH reduced mean and median lengths and significantly increased mean and median diameters. The authors suggested KOH may have dissolved some thinner fibers
  • Kevlar aramid: lengths could not be measured because the fibers are curly. Bleach-treated Kevlar diameters were significantly reduced compared with saline- or KOH-treated fibers
  • Pan-based carbon fibers: lengths were significantly reduced after bleach compared with saline- or KOH-treated fibers. Diameters were uniformly 4.4 µm and were not altered by bleach or KOH
  • In a follow-up count by phase contrast light microscopy, fewer glass fibers per square millimeter of filter were found after KOH (11.4) than after saline (18.7) or bleach (17.9). Wollastonite counts were 6.6 (saline), 5.4 (bleach) and 6.0 (KOH) per square millimeter
• The authors' conclusion: The authors concluded that lung digestion procedures using caustic materials may alter fiber dimensions, and that digestion methods should be assessed for each fiber type before starting fiber clearance studies
• Limitations the authors state:
  • No fiber-containing lung tissue was digested, so the procedure may not accurately simulate real fiber recovery. Lung tissue may protect fibers from the digestion agents
  • The study was not designed to show a specific effect of bleach or KOH on any particular fiber type
  • The authors stated there was no satisfactory explanation for the increase in glass fiber diameters after KOH

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Jeffrey mine, Asbestos, Quebec

All asbestos mines

Topics

Medical terms in this study, explained in our Lexicon: Aspect Ratio (Length-to-diameter ratio), Tissue Digestion, Crocidolite, Chrysotile, Wollastonite, Scanning Electron Microscopy (SEM), Fiber Length, Fiber Clearance.

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