Quality control of airborne asbestos fibre counts in the United Kingdom--the present position

Our plain-English summary of Quality control of airborne asbestos fibre counts in the United Kingdom--the present position, by N.P. Crawford, A.J. Cowie (The Annals of Occupational Hygiene, 1984).

The study

• Authors: N.P. Crawford, A.J. Cowie
• Journal: The Annals of Occupational Hygiene
• Published: 1984;28(4):391-8
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The United Kingdom Central Reference Scheme for asbestos counting has been expanded by initiating a series of regular interlaboratory counting exchanges (RICE) to minimize national within- and between-laboratory differences in asbestos fibre counts obtained by the membrane filter method. The scope of the present RICE operation is described and results are presented depicting current interlaboratory differences. National scatter is unacceptably large; up to ten-fold systematic differences occur between visual-counting laboratories, whilst random differences in counts of up to 100-fold occur on the same sample. For the reference samples evaluated, counts made by Magiscan automated image analysers are generally near the national mean and differences between Magiscans are usually small compared with differences between visual-counting laboratories. Results obtained by an experienced group of laboratories relative to Magiscan have been used to derive a categorization procedure for assessing laboratory performance. Some details are given concerning future operation of RICE with a view to improving national reproducibility. A European-based scheme similar to RICE is needed to help ensure that the community asbestos directive applies uniformly in CEC countries.

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

In plain English

This paper described the United Kingdom's scheme of regular interlaboratory counting exchanges (RICE). The scheme was set up to reduce differences between laboratories that count airborne asbestos fibres on membrane filters. The paper reported the scheme's position as of December 1983. It was not a study of workers' health. About 100 visual-counting laboratories took part. They counted batches of eight reference samples collected mainly during asbestos product manufacture or delagging. Magiscan automated image analysers also counted the same samples. The authors reported that national scatter was unacceptably large: around ten-fold systematic differences between laboratories, and random differences of up to 100-fold on the same sample. For the samples evaluated, Magiscan counts lay near the national mean, and differences between Magiscans were generally small compared with differences between laboratories. In a group of five experienced laboratories, the median ratio of laboratory counts to Magiscan counts was 1.3, with an interlaboratory coefficient of variation around 40%. From these results the authors proposed limits for sorting laboratories into three performance categories. Three of the five experienced laboratories met category 1. The authors concluded that a similar European scheme was needed.

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: Description of a national interlaboratory quality-control scheme for asbestos fibre counting (RICE), with results of its counting exchanges and a proposed laboratory categorization procedure
• Who was studied: About 100 visual-counting laboratories in the United Kingdom, in groups of 5-6. Results were also given for the five experienced Central Reference Scheme (CRS) laboratories and for counts by three Magiscan automated image analysers. The position was as at December 1983.
• Exposure: Not a health exposure study. The material counted was reference membrane-filter samples collected mainly during the manufacture of asbestos products or during delagging. Sample types were delagging, asbestos cement, friction material and textile. Fibre types were not specified.
• Main results:
  • Across UK laboratories, there were around ten-fold systematic differences between laboratories and random differences of up to 100-fold on the same sample
  • In the second round, the highest-counting CRS laboratory (group 01) produced counts around 1.75 times those of Magiscan L. The lowest laboratory in group 06 produced about one-tenth of the counts of Magiscan M.
  • For the sample batches evaluated, Magiscan counts lay near the national mean, and differences between Magiscans were generally small compared with differences between visual-counting laboratories
  • Within the five CRS laboratories, maximum systematic differences were about 3-fold, compared with about 10-fold nationally
  • Over 32 samples counted by the CRS laboratories, the median ratio of laboratory count to Magiscan count was 1.3, with an interlaboratory coefficient of variation around 40%
  • The proposed category 1 limits were ratios of 0.65 to 2.6, and category 2 limits were 0.45 to 3.8. In each case at least 75% of a laboratory's ratios over 32 consecutive samples had to fall within the limits. Laboratories not meeting these were category 3.
  • Among the five CRS laboratories, B, C and D met the category 1 conditions; A and E did not
• The authors' conclusion: The authors concluded that national scatter in counts was unacceptably large. They stated that a European quality-control scheme like RICE was needed to control subjective differences and help the Community Asbestos Directive apply uniformly in CEC countries.
• Limitations the authors state:
  • A laboratory's performance could not be compared immediately with laboratories outside its own group
  • RICE did not yet standardize the laboratories' evaluation methods
  • Low-density samples relevant to clearance work were not yet included, because counts vary more at lower densities

Topics

Medical terms in this study, explained in our Lexicon: Membrane Filter Method.

Related studies

• Surveillance of high-risk groups--a survey of asbestos workers: the present position in the United Kingdom — W.J. Smither (1979)
• Within-laboratory quality control of asbestos counting — T.L. Ogden, T. Shenton-Taylor, et al. (1986)
• Asbestos lung fibre analysis in the United Kingdom, 1976-96 — G. Berry (2002)
• Variation in fibre and dust counts in an asbestos mine and mill — R.C. Parsons, D.G. Bryant, et al. (1986)
• Study of the count-to-mass conversion factor for asbestos fibres in samples collected at the emissions of three industrial plants — S. Puledda, A. Marconi (1991)
• Historical ambient airborne asbestos concentrations in the United States — M.M. Finkelstein (2016)

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