Comparison of AIA and NIOSH methods on asbestos fibre measurements in the workplace

Our plain-English summary of Comparison of AIA and NIOSH methods on asbestos fibre measurements in the workplace, by E. Gonzalez-Fernandez, P.D. de la Osa, F.R. Martín (The Annals of Occupational Hygiene, 1987).

The study

• Authors: E. Gonzalez-Fernandez, P.D. de la Osa, F.R. Martín
• Journal: The Annals of Occupational Hygiene
• Published: 1987;31(3):363-73
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

In plain English

This study compared two standard methods for counting airborne asbestos fibres collected on membrane filters under a phase-contrast microscope: the US NIOSH method P & CAM 239 and the Asbestos International Association (AIA) method RTM 1. The authors took 176 samples in matched pairs (88 by each method) at four workplaces in a chrysotile and crocidolite asbestos-cement factory in 1982 and 1983. On average, the AIA method gave concentrations 71% lower than the NIOSH method (mean ratio 0.29). When 54 filters collected by the NIOSH method were also prepared and counted by AIA rules, the AIA counts were 65% lower (ratio 0.35). The statistical analysis indicated that the difference came from how filters were mounted and counted, not from how the air was sampled. Fitting a cowl to the AIA sampling head made no significant difference. The NIOSH results were compared with the OSHA standard of 2 fibres per ml. This showed five situations of risk, three of no risk and two with no decision. Under the AIA results, all workplaces would have been judged compliant. The authors concluded that the relationship between the methods may not be the same in all asbestos workplaces.

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: Field comparison of two air-sampling and fibre-counting methods using matched pairs of personal samples, with an additional comparison of counting rules on the same filters and a test of cowled versus uncowled sampling heads
• Who was studied: Air samples, not people: 176 samples (88 on 37 mm filters by the NIOSH method, 88 on 25 mm filters by the AIA method) taken at four workplaces in one asbestos-cement factory in January, March and April 1982 and January 1983
• Exposure: Airborne asbestos fibres in a factory making asbestos cement from chrysotile and crocidolite. The four workplaces were mill loading and mixing, big pipe turning, small pipe turning and pipe cutting.
• Main results:
  • For the full methods (sampling plus counting), the overall AIA/NIOSH mean ratio was 0.29 plus or minus 0.04. AIA concentrations were 71% (range 67-75%) lower than NIOSH concentrations.
  • For 54 samples all collected by the NIOSH method but mounted and counted by both methods, the overall AIA/NIOSH mean ratio was 0.35 plus or minus 0.05. The AIA method counted 65% (range 60-70%) fewer fibres.
  • The full NIOSH method gave significantly higher mean concentrations than both the full AIA method and NIOSH-collected samples counted by AIA rules. There was no significant difference between those two AIA-counted groups, so the authors attributed the difference to mounting and counting rather than to sampling.
  • Pooled coefficients of variation were 14.4% for all AIA counts and 17.8% for all NIOSH counts. The difference was not significant.
  • The NIOSH results were evaluated against the OSHA standard of 2 fibres per ml at 95% confidence. This gave five situations of risk, three of no risk and two with no decision.
  • Under the same criteria, the AIA results would have placed all workplaces in compliance.
  • Personal samples taken by the AIA method with a metallic cowl, with a plastic cowl or without a cowl showed no significant difference.
• The authors' conclusion: The authors concluded that the AIA method gives on average 71% lower fibre concentrations than the NIOSH method, so very different conclusions can be reached in a workplace risk evaluation. They attributed this to differences in mounting and counting rather than sampling, and found that a cowl had no significant effect.
• Limitations the authors state:
  • The authors noted that the relationship between the two methods may not be constant: it may vary with asbestos type and with the source of the sample. The finding may therefore not apply to all asbestos workplaces.

Topics

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

Medical terms in this study, explained in our Lexicon: NIOSH.

Related studies

• Comparison of NIOSH and AIA methods for evaluating asbestos fibres: effects of asbestos type, mounting medium, graticule type and counting rules — E. Gonzalez-Fernandez, F.R. Martín (1986)
• A comparison of parallel dust and fibre measurements of airborne chrysotile asbestos in a large mine and processing factories in the Russian Federation — E. Feletto, S.J. Schonfeld, et al. (2017)
• A comparison of historic asbestos measurements using a thermal precipitator with the membrane filter-phase contrast microscopy method — G. Burdett (1998)
• The influence of external aerodymanic factors on the measurement of the airborne concentration of asbestos fibres by the membrane filter method — A.M. Johnston, A.D. Jones, et al. (1982)
• NIOSH's Respiratory Health Division: 50 years of science and service — K.J. Cummings, D.O. Johns, et al. (2019)
• Exposure science will not increase protection of workers from asbestos-caused diseases: NIOSH fails to provide needed public health action and leadership — R.A. Lemen, H. Anderson, et al. (2011)

Browse more research in The Annals of Occupational Hygiene, or return to medical research.