Hygiene Standards For Chrysotile Asbestos Dust The British Occupational Hygiene Society

Our plain-English summary of Hygiene Standards For Chrysotile Asbestos Dust The British Occupational Hygiene Society, by R.E. Lane, J.C. Gilson, S.A. Roach, et al (1968).

The study

• Authors: R.E. Lane, J.C. Gilson, S.A. Roach, S. Smith, C.G. Addingley, S. Holmes, R. Hunt, J.F. Knox, E. King
• Published: British Occupational Hygiene Society (1968)
• Type of article: Report
• Our copy: from Johns-Manville's own medical library. The article is still under copyright, so we describe it here rather than post it.

In plain English

This 1968 report by a committee of the British Occupational Hygiene Society set out hygiene standards for airborne chrysotile asbestos dust. The standard rested mainly on a survey of 290 men at one asbestos textile factory. All had been first employed after 1 January 1933 and had worked there for 10 years or more. Of these men, 16 had basal rales (crackling sounds at the base of the lungs) and 8 had X-ray changes that were possibly due to asbestos. The committee combined these findings with dust measurements. It estimated that a 1 per cent risk of basal rales went with an accumulated exposure of 112 fibre years per cm³, which equals 2.2 fibres per cm³ for 50 years. To be 95 per cent sure the risk was under 1 per cent, the level would have to be 1.0 fibres per cm³. The authors aimed to keep the risk of the earliest signs of asbestosis to 1 per cent. They noted several limits: the data were scanty, dust records began only in 1951, and men who had left the industry were not included. They also said no dust level could yet be named as free of cancer risk.

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: Committee report recommending hygiene standards for chrysotile dust. It was based mainly on a clinical and X-ray survey of workers at one asbestos textile factory, analysed with a statistical risk-exposure model (probit analysis).
• Who was studied: 290 men at an asbestos textile factory in Britain, first employed after 1 January 1933 and employed for 10 years or more. They were assessed as at 30 June 1966 and divided into two groups: Fiberising plus Carding and Spinning (Group 1), and Weaving plus Plaiting (Group 2).
• Exposure: Chrysotile asbestos dust in textile processes, measured with thermal precipitators and membrane filters. Exposure was expressed as fibres longer than 5 μ per cm³, summed over years of exposure (fibre years/cm³).
• Main results:
  • Among the 290 men, 16 had basal rales and 8 had X-ray changes considered possibly asbestotic. The authors note that the 16 includes 3 suspensions for asbestosis.
  • For basal rales, a 1 per cent risk was estimated at an exposure of 112 fibre years/cm³, that is 2.2 fibres/cm³ for 50 years.
  • At 2.2 fibres/cm³, the authors said there was a reasonable chance that the risk of basal rales was as high as 3 per cent.
  • To state with 95 per cent probability that the risk was less than 1 per cent over 50 years, the concentration would need to be 1.0 fibres/cm³.
  • For X-ray changes, a 1 per cent risk was estimated at 2.6 fibres/cm³ for 50 years. The authors said this estimate was less well determined because fewer men had X-ray changes.
• The authors' conclusion: The committee concluded that the risk of the earliest clinical signs of asbestosis is probably less than 1 per cent for an accumulated exposure of 100 fibre years per cm³. It recommended dust categories based on 3-month average concentrations: Negligible 0 to 0.4, Low 0.5 to 1.9, Medium 2.0 to 10.0, and High over 10.0 fibres/cm³. It also recommended medical examinations before employment and annually thereafter.
• Limitations the authors state:
  • The data were scanty and based on factory experience of continuous exposure during working hours. The authors advised caution in applying the standards to other patterns of exposure.
  • For some men exposure began in 1933, but dust records did not start until 1951.
  • Only men still working were studied. If men who had left differed in their susceptibility to asbestosis, the conclusions would be biased.
  • With the small amount of data, the exposure giving a 1 per cent risk could be estimated only imprecisely.
  • The quantitative relationship between asbestos and cancer was not known, so no air concentration could be specified as free of cancer risk.

Topics

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

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