Measurement of airborne asbestos dust by instruments measuring different parameters

Our plain-English summary of Measurement of airborne asbestos dust by instruments measuring different parameters, by S.A. Roach (Annals of the New York Academy of Sciences, 1965).

The study

• Author: S.A. Roach
• Journal: Annals of the New York Academy of Sciences
• Published: 1965;132(1):306-15
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy.

In plain English

This paper compared ways of measuring airborne dust in one department of an asbestos factory that disintegrated crude amosite fiber. Microscope examination showed the dust was mostly short, thin, straight fibers. About 84 per cent of visible particles were shorter than 1 micron; 0.6 per cent were thicker than 1 micron. Eight instruments were run side by side: four counted particles and four measured dust mass. Counts depended on the instrument and microscope used. Membrane filter fiber counts rose from 0.06 to 0.48 million fibers per cubic foot with a stronger microscope lens. Recorded dust levels were much lower than the ACGIH limit of 5 million particles per cubic foot. All-sizes samplers gave 1.06 and 0.94 mg per cubic metre; respirable-dust samplers gave 0.34 (UNICO) and 0.29 (Hexhlet). The author concluded that weighing a dust sample was quicker and more accurate than counting by eye, and judged the UNICO sampler the best available type for measuring these workers' exposure. The author noted that no instrument tried was very suitable for measuring dust inhaled by someone wearing a face mask.

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 dust-measuring instruments run side by side in one department of an asbestos factory
• Who was studied: Airborne dust in one department of an asbestos factory where crude amosite fiber was disintegrated. The measurements were meant to reflect the workers' exposure, including that of a bagging machine operator. The readable text does not give the factory's location or the sampling dates.
• Exposure: Airborne amosite dust from disintegrating crude amosite fiber. It was measured as particle and fiber counts (midget impinger, membrane filter, thermal precipitator, Royco counter) and as mass concentration (electrostatic precipitator, Casella instruments, UNICO respirable dust sampler).
• Main results:
  • In thermal precipitator samples, particles shorter than 1 micron made up 84 per cent of all visible particles, and only five per cent were longer than five microns
  • In the same samples, 94 per cent of particles were less than 0.5 microns wide and only 0.6 per cent were thicker than one micron
  • The dust levels recorded in the study were much lower than the ACGIH Threshold Limit Value of 5 million particles per cubic foot
  • The midget impinger mean is printed as '11' million particles per cubic foot in the scanned text. This reading was taken to be 1.1, with a decimal point lost in scanning. The reading rests on two things the article states: dust levels were much lower than the 5 million limit, and that limit converts to about 1.5 mg per cubic metre of respirable dust. That conversion fits 1.1 alongside the measured 0.34 and 0.29 mg per cubic metre. The value should be checked against the printed page.
  • Membrane filter fiber counts were 0.06 million fibers per cubic foot under a 16 mm objective and 0.48 under a 2 mm objective (values confirmed by Table 4). The thermal precipitator gave higher counts again.
  • Mass concentration from the electrostatic precipitator (all sizes) was 1.06 mg per cubic metre
  • Mass concentration from the second all-sizes sampler was 0.94 mg per cubic metre
  • Respirable dust measured by the UNICO sampler was 0.34 mg per cubic metre
  • Respirable dust measured by the Hexhlet was 0.29 mg per cubic metre
  • The ACGIH standard of five million particles per cubic foot appeared to correspond to about 1.5 mg per cubic metre of respirable dust in this type of dust cloud
  • The works' own standard was no more than four fibers per ml, measured with the membrane filter method. This corresponded to about 0.1 mg per cubic metre of respirable dust.
  • Dust at the nearest house to the plant was too small to measure
• The authors' conclusion: The author concluded that measuring mass concentration was simpler than counting particles, because it was quicker and more accurate. The author judged the UNICO respirable dust sampler the best available type for measuring these workers' exposure. The midget impinger was seen as suited to workplace inspection against ACGIH standards, and the Royco counter to locating sources of heavy exposure. The author said the choice of sampler depends on the circumstances.
• Limitations the authors state:
  • None of the instruments tried was very suitable for measuring the dust concentration actually inhaled by someone wearing a face mask
  • The Royco counter's calibration for fibrous dust is uncertain
  • Particle and fiber counts depended on the sampling instrument and the counting method, and the finest fibers were too thin to be resolved by the light microscope

Related studies

• Dust measurement and monitoring in the asbestos industry — C.G. Addingley (1965)
• Developments in dust sampling and counting techniques in the asbestos industry — S. Holmes (1965)
• Present threshold limit value in the U.S.A. for asbestos dust: a critique — E.L. Schall (1965)
• Economics of dust control — D.W. Hills (1965)
• Asbestos dust--a community hazard? — (1969)
• 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)

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