Measurement of dust exposures in the asbestos textile industry

Our plain-English summary of Measurement of dust exposures in the asbestos textile industry, by J.R. Lynch, H.E. Ayer (American Industrial Hygiene Association Journal, 1966).

The study

• Authors: J.R. Lynch, H.E. Ayer
• Journal: American Industrial Hygiene Association Journal
• Published: 1966;27(5):431-7
• Cited by: 21 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 002527).

Abstract

Data obtained from environmental surveys of nine asbestos textile mills, which represent the baseline for the textile segment of the Public Health Service epidemiological study of asbestos processing industries, are presented. From these data concentration ranges are derived which yield significant differences between typical sample groups. Variance ratio tests of different methods of counting and analysis were made and count weight ratios based on magnesium analyses for asbestos were calculated.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.

In plain English

This U.S. Public Health Service paper reported dust measurements from environmental surveys of nine asbestos textile plants, carried out between January 1964 and June 1965. The surveys were the baseline for an epidemiological study of over 2,500 employees. The authors collected 1,896 membrane filter samples and 1,115 impinger samples. Impinger dust levels were generally below the Threshold Limit Value then in use, 5 million particles per cubic foot. Membrane filter counts under phase contrast found eight times as many fibers as impinger counts. Most fibers were probably too thin to see by light microscopy. The two methods ranked plant operations the same in 75% of cases using three concentration groups, and in 50% using six body-burden groups. Statistical tests found no counting method significantly less variable than the others. Magnesium analysis of 250 samples gave about 11,000 total fibers per microgram of asbestos. The authors concluded that dustiness categories must be broad. They found it difficult to reconcile standards based on grain-dominated counts with fibers being thought to cause disease.

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: Industrial hygiene environmental (workplace air) survey with statistical comparison of dust sampling and counting methods
• Who was studied: Nine U.S. asbestos textile plants (labeled A to I), surveyed from January 1964 to June 1965; the plants provided a cohort of over 2,500 employees for a Public Health Service epidemiological study
• Exposure: Airborne asbestos textile dust by plant and operation (fiber preparation, carding, spinning, twisting, winding, weaving). It was measured by impinger counts of grains and fibers, membrane filter fiber counts (total, longer than 5 microns, longer than 10 microns), electron microscopy, and magnesium analysis for chrysotile asbestos.
• Main results:
  • In the nine plants, dust concentrations measured by impinger were generally below the Threshold Limit Value of 5 mppcf
  • Total fiber concentration by optical membrane filter counts under phase contrast was eight times that found on comparable impinger samples counted at 100X light field
  • Most fibers, even those longer than 3 microns, were not counted by either the impinger or the optical membrane filter method, probably because they were too thin for light microscopy
  • A fourfold difference in concentration was needed for significance at p = 0.05, so the data were divided into three concentration groups
  • Using the three concentration groups, impinger and membrane filter total fiber counts gave the same estimate of relative dustiness in 75% of cases, and never differed by more than one group
  • Using the six narrower body-burden groups, only 50% of sample sets fell in the same group by both methods; fewer than 10% differed by more than one group
  • Results were more uniform for different operations within a plant than for the same operation in different plants, which the authors attributed to plant dust-control effort
  • Variance ratio tests found no statistically significant difference in variability between the counting methods compared, so none could be considered less variable than the others
  • From magnesium analysis of 250 membrane filter samples, the approximate count-weight ratios were 11,000 total fibers, 5,000 fibers longer than 5 microns, and 3,000 fibers longer than 10 microns per microgram of asbestos
  • The three sets of count-weight ratios followed a log normal distribution with the same geometric standard deviation of 2.3, so no count type was preferred as an estimate of mass
  • Electron micrograph size distributions gave an independent count-weight ratio of 8000 fibers per microgram, the same order of magnitude as the magnesium results
  • About 1 mg per cubic meter of asbestos was estimated to be roughly equivalent to 1 mppcf by impinger, suggesting mass concentrations may be higher than previously assumed
  • Preliminary results put the respirable fraction at about 50 to 60% by elutriator and 30 to 40% by cyclone
• The authors' conclusion: The authors concluded that dustiness categories must be broad because of natural variability in the workplace. They also concluded that basing hygienic criteria on impinger counts dominated by grains is hard to reconcile with fibers being thought to cause disease, so counting fibers on membrane filters appeared to have an advantage.
• Limitations the authors state:
  • Non-fibrous serpentine contributes magnesium but not fibers, so the magnesium method tends to overestimate the mass of fibrous asbestos, and little can be done about this
  • The relationship between mass concentration and impinger counts was developed by a very indirect method
  • Not all magnesium analyses for the respirable-fraction samples were completed; those results were preliminary
  • The relevance of magnesium analysis for asbestos is unknown, and it requires expensive equipment not generally available

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestos textiles.

Medical terms in this study, explained in our Lexicon: Asbestos Textile Industry.

Related studies

• Estimates of historical exposures by phase contrast and transmission electron microscopy in North Carolina USA asbestos textile plants — J.M. Dement, D. Myers, et al. (2009)
• Occupational exposure to textile dust and lung cancer risk: Results from the ICARE Study — S. Ben Khedher, M. Neri, et al. (2018)
• Quantitative X-ray diffraction analysis of crocidolite and amosite in bulk or settled dust samples — J.V. Crable, M.J. Knott (1966)
• Dust exposure and mortality in an American chrysotile textile plant — A.D. McDonald, J.S. Fry, et al. (1983)
• Dust exposure and mortality in an American factory using chrysotile, amosite, and crocidolite in mainly textile manufacture — A.D. McDonald, J.S. Fry, et al. (1983)
• Dust control in a conventional asbestos textile factory — H.C. Lewinsohn, C.A. Kennedy, et al. (1979)

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