Conversion of the asbestos fibre concentration recorded by means of the konimeter and the thermal precipitator to that expected by means of the membrane filter method

Our plain-English summary of Conversion of the asbestos fibre concentration recorded by means of the konimeter and the thermal precipitator to that expected by means of the membrane filter method, by R.S. du Toit, T.C. Gilfillan (The Annals of Occupational Hygiene, 1979).

The study

• Authors: R.S. du Toit, T.C. Gilfillan
• Journal: The Annals of Occupational Hygiene
• Published: 1979;22(1):67-83
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Previously published relationships between asbestos fibre concentrations recorded by means of the Konimeter, the TP and with membrane filters are re-presented in a more convenient form to facilitate conversion of Konimeter and TP data to membrane filter equivalents.

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

In plain English

This short communication did not report new measurements. The authors re-presented relationships they had published in 1977 between asbestos fibre concentrations measured with three sampling methods: the Konimeter, the thermal precipitator (TP), and the membrane filter method. Their aim was to make it easier to convert Konimeter and TP readings into the concentrations expected with membrane filters. They gave separate formulas and tables for Cape crocidolite, Transvaal crocidolite, chrysotile and amosite. Conversion went first to filters of 8 micrometre pore size and then to 0.8 micrometre pore size. For Cape crocidolite, readings on the two filter sizes had a correlation coefficient of 0.683 (19 degrees of freedom). The authors reported that both the Konimeter and the TP underestimated concentrations compared with 0.8 micrometre filters, less so at higher concentrations. In the range of 2 to 5 fibres per cm3, the underestimation was by a factor of about 2 for Cape crocidolite. By Konimeter it was about 3 to 5 for the other three types. Those figures assumed the Cape crocidolite filter relationship applied to the other types. The authors argued the true factors were likely closer to one, because those fibres are coarser.

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: Short communication re-presenting regression relationships from the authors' own earlier (1977) study as conversion formulas, tables and graphs; a measurement-methods paper, not a health study
• Who was studied: No people were studied. The paper used airborne asbestos fibre concentration data from the authors' 1977 study, including Cape crocidolite sampled in the Polley dust duct. No place or date of sampling beyond this is given.
• Exposure: Airborne fibre concentrations of four asbestos types (Cape crocidolite, Transvaal crocidolite, chrysotile, amosite) as measured by Konimeter, thermal precipitator, and membrane filters of 8 and 0.8 micrometre pore size
• Main results:
  • For Cape crocidolite, the correlation coefficient between 8 and 0.8 micrometre pore size filter results was 0.683, with 19 degrees of freedom, reported as significant at the 99% confidence level
  • Both the Konimeter and the thermal precipitator underestimated fibre concentration compared with 0.8 micrometre pore size membrane filters
  • The underestimation decreased as concentration increased
  • For Cape crocidolite in the 2 to 5 fibres per cm3 range, the underestimation was by a factor of the order of 2
  • For Transvaal crocidolite, chrysotile and amosite, the conversion factor by Konimeter was of the order of 3 to 5 in the 2 to 5 fibres per cm3 range. This assumes the Cape crocidolite filter relationship holds for these types.
  • By thermal precipitator in the 2 to 5 fibres per cm3 range, the conversion factors were 3.6 to 2.2 for Transvaal crocidolite, 6.0 to 3.2 for chrysotile, and 6.5 to 4.8 for amosite
• The authors' conclusion: The authors concluded that both instruments underestimate fibre concentration relative to 0.8 micrometre filters. They argued that the true conversion factors for Transvaal crocidolite, chrysotile and amosite are likely closer to unity than the figures quoted, because these fibres are coarser than Cape crocidolite.
• Limitations the authors state:
  • Conversion to 0.8 micrometre filter values for the three non-Cape asbestos types assumes that the 8 to 0.8 micrometre relationship measured for Cape crocidolite also holds for them
  • The 8 to 0.8 micrometre filter relationship for the other three asbestos types had not yet been investigated
  • The other three types are coarser than Cape crocidolite, so the 8 micrometre filter likely underestimates them less, and the quoted factors may be too high

Topics

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

Related studies

• A comparison of historic asbestos measurements using a thermal precipitator with the membrane filter-phase contrast microscopy method — G. Burdett (1998)
• Simultaneous airborne dust samples with konimeter, thermal precipitator and dosimeter in asbestos mines — R.S. du Toit, T.C. Gilfillan (1977)
• Review of early results of comparative tests with the konimeter and the thermal precipitator in asbestos mines — R.S. Du Toit (1977)
• 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)
• Comparison of a fibrous aerosol monitor (FAM) with the membrane filter method for measuring airborne asbestos concentrations — P.J. Iles, T. Shenton-Taylor (1986)
• A comparison of fibre counting stopping rules in the application of the membrane filter method — N.P. Crawford, W.M. Maclaren, et al. (1987)

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