Simultaneous airborne dust samples with konimeter, thermal precipitator and dosimeter in asbestos mines

Our plain-English summary of Simultaneous airborne dust samples with konimeter, thermal precipitator and dosimeter in asbestos mines, by R.S. du Toit, T.C. Gilfillan (The Annals of Occupational Hygiene, 1977).

The study

• Authors: R.S. du Toit, T.C. Gilfillan
• Journal: The Annals of Occupational Hygiene
• Published: 1977;20(4):333-44
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Simultaneous airborne dust samples were taken with three types of instruments: konimeter, thermal precipitator and dosimeter (personal sampler with membrane filter) in eight asbestos mines producing four types of asbestos (Cape crocidolite, Transvaal crocidolite, amosite and chrysotile). Additional tests were carried out in a dust duct with a specific type of asbestos fibre at a steady dust concentration. The filtering efficiencies of 8 and 0.8 µm pore size membrane filters used in the dosimeter were compared. The statistical analyses of the results have been summarised and formulae are given to convert the fibre concentrations recorded by the konimeter and the thermal precipitator into that expected with the membrane filter method of sampling.

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

In plain English

This study compared three instruments for measuring airborne asbestos dust in South African mines: the konimeter, the thermal precipitator and the dosimeter (a personal sampler with a membrane filter). Three of each ran side by side in eight mines producing Cape crocidolite, Transvaal crocidolite, chrysotile and amosite (24 tests). Three further tests used Cape crocidolite in a laboratory dust duct. Fibres counted were 5 to 100 micrometres long, under 5 micrometres in diameter, and over three times as long as wide. Instruments of the same type did not differ significantly from one another. For each asbestos type, the authors derived formulas converting fibre concentrations recorded by konimeters and thermal precipitators into those expected with dosimeters using 8 micrometre pore filters, as used in the mines. They noted wide scatter and correlation coefficients "on the low side". Konimeter and thermal precipitator results were related, but differently for each asbestos type. In the Cape crocidolite duct tests, 0.8 micrometre pore filters recorded higher concentrations than 8 micrometre filters at lower concentrations, and a separate formula linked them. The authors concluded the relationships might be of some use for conversion, but that conversion would be complicated and laborious.

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 three dust-sampling instruments run simultaneously in eight asbestos mines, with statistical (regression) analysis, plus laboratory dust-duct tests comparing two membrane filter pore sizes
• Who was studied: Air sampled at eight asbestos mines in South Africa, at development, stope and mill sites (24 mine tests), followed by 3 tests in a Polley dust duct
• Exposure: Airborne fibres of Cape crocidolite, Transvaal crocidolite, chrysotile and amosite. Particles were counted as fibres if they were less than 5 micrometres in diameter, had a length-to-width ratio greater than 3 to 1, and were 5 to 100 micrometres long. UICC Cape crocidolite was used in the dust-duct filter comparison.
• Main results:
  • Konimeters: of 693 statistical (Friedman) tests comparing the three konimeters, only 17 showed a significant difference. The authors concluded there was no significant difference between the three instruments.
  • Thermal precipitators: only 1 of 24 tests showed a significant difference between the three instruments. The three sets of dosimeter readings were also not significantly different.
  • 8 micrometre pore membrane filters were used in the dosimeters during the mine tests. The mine-based conversion relationships are to the dosimeter with 8 micrometre pore filters. The regression equations were based on transformed readings, using the mean of transformed values from two, three or four konimeter slides or thermal precipitator readings.
  • For Cape crocidolite, thermal precipitator versus dosimeter was the only one of the 12 comparisons where no correlation appeared to exist. After the dust-duct data were merged with the mine data, the correlation coefficient was 0.6767, and the authors considered the resulting equation usable with some confidence.
  • Konimeter and thermal precipitator results were related, but with a different relationship for each type of asbestos. Both were related to dosimeter results, although with wide scatter.
  • In dust-duct tests with Cape crocidolite, 0.8 micrometre pore filters recorded higher concentrations than 8 micrometre pore filters. For example, 2 f/cm3 on 8 micrometre filters corresponded to 3.2 f/cm3 on 0.8 micrometre filters. A separate conversion formula between the two pore sizes was derived from the first 18 pairs of observations.
  • The conversion factor from 8 micrometre to 0.8 micrometre filters fell as concentration rose: 4.6 at 1 f/cm3 compared with 1.1 at 10 f/cm3. The two filter pore sizes were suggested to record the same concentration at about 13 f/cm3.
• The authors' conclusion: The authors concluded that the relationships found might be of some use for converting konimeter and thermal precipitator fibre concentrations into those expected with the membrane filter method, but that the conversion would be complicated and laborious.
• Limitations the authors state:
  • The two filter pore sizes were compared only with UICC Cape crocidolite. Whether the same conversion formula applies to other asbestos types was left for later investigation.
  • The correlation coefficients for the regression equations were on the low side.
  • There was wide scatter in the relationships between dosimeter results and konimeter and thermal precipitator results.

Topics

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

Related studies

• Relationships between simultaneous airborne dust samples taken with five types of instruments at South African asbestos mines and mills — R.S. Du Toit, L.W. Isserow, et al. (1983)
• Review of early results of comparative tests with the konimeter and the thermal precipitator in asbestos mines — R.S. Du Toit (1977)
• 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 — R.S. du Toit, T.C. Gilfillan (1979)
• 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)
• Evidence and reconstruction of airborne asbestos from unconventional environmental samples — J.S. Webber, M. Getman, et al. (2006)

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