Fibre Concentrations and Size Distributions of Airborne Fibres in Several European Man-Made Mineral Fibre Plants

Our plain-English summary of Fibre Concentrations and Size Distributions of Airborne Fibres in Several European Man-Made Mineral Fibre Plants, by J. Dodgson, J. Ottery, J.W. Cherrie, et al (1980).

The study

• Authors: J. Dodgson, J. Ottery, J.W. Cherrie, G.E. Harrison
• Published: BIOLOGICAL EFFECTS OF MINERAL FIBRES (J.C. WAGNER, EDITOR), LYON: IARC SCIENTIFIC PUBLICATIONS, VOLUME 30, PP. 913-925 (1980)
• Type of article: Conference paper
• 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 paper reported air measurements of man-made mineral fibres, not asbestos, at five European plants. Three made glass wool (plants B, D and F) and two made rock wool (plants C and G); all were part of a Joint European Medical Research Board health study. At least 20% of workers in each job group, chosen at random, wore personal air samplers during their shift. In production jobs, average fibre concentrations were lower at the glass wool plants than at the rock wool plants. The highest production values were 0.206 respirable and 0.261 non-respirable fibres/ml. Secondary processes generally had higher levels. The highest values, 1.889 respirable and 1.240 non-respirable fibres/ml, were recorded while special fine fibres were packed at plant D. Median fibre diameters ranged from 0.75 to 1.6 um. Compared with published data on airborne asbestos, the man-made fibres tended to be longer and thicker. The authors suggested that, if fibre shape rather than chemical makeup governs biological activity, this may mean a smaller potential for cancer than with asbestos. The paper did not examine disease in workers.

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: Occupational hygiene survey using personal air sampling, part of the environmental studies for a European epidemiological study of man-made mineral fibre workers; results for 5 of 13 plants
• Who was studied: Workers at five European man-made mineral fibre plants: three glass wool plants (B, D, F) and two rock wool plants (C, G). Not less than 20% of workers in each occupational group were randomly selected to wear samplers. These were 5 of 13 plants in seven countries chosen for a historical follow-up study.
• Exposure: Airborne man-made mineral fibres from glass wool (TEL process) and rock wool production. They were measured as respirable fibres (length over 5 um, diameter under 3 um, aspect ratio over 3) and non-respirable fibres (diameter over 3 um), in fibres/ml. Job groups were production, secondary processes and miscellaneous. Asbestos (amosite, chrysotile, crocidolite) appeared only as comparison data from other published studies.
• Main results:
  • In the production group, mean fibre concentrations at the glass wool plants were lower than at the rock wool plants. Mean respirable concentrations in production were 0.018, 0.014 and 0.004 fibres/ml at glass plants B, D and F, and 0.053 and 0.027 fibres/ml at rock plants C and G.
  • The highest production-group concentrations measured were 0.206 respirable fibres/ml and 0.261 non-respirable fibres/ml. The authors described these as not particularly high if recommended asbestos exposure levels are used as a standard.
  • Fibre concentrations were generally higher in the secondary processes group (moulding, cutting, sawing, packing, etc.), which also showed a greater range.
  • The highest values in the survey were 1.889 respirable fibres/ml and 1.240 non-respirable fibres/ml, during packing of special fine fibres at plant D.
  • Fibre length distributions were approximately log-normal. They differed significantly between plants, except between plants F and B.
  • Across the five plants, median fibre lengths were correlated with median diameters (correlation coefficient 0.78), with longer fibres associated with larger diameters.
  • On average, the man-made mineral fibres tended to be longer and to have larger median diameters than airborne asbestos fibres reported in other studies.
  • Fibres from the rock wool plants tended to have larger diameters than those from the glass wool plants.
  • Median fibre diameters in this study were 0.75 to 1.6 um, compared with about 3 to 6 um reported in American plants by another research group, Esmen et al.
  • The percentage of airborne fibres with diameters less than 0.5 um varied from 35% at plant D to 10% at plant G.
• The authors' conclusion: The authors stated that their fibre size data, compared with asbestos data, would imply that a smaller potential for carcinogenicity may exist with man-made mineral fibres than with asbestos. This was conditional on fibre shape, rather than chemistry, governing biological activity. They noted that there had been no reports of carcinogenicity in man from man-made mineral fibre exposure, or in animals from inhalation studies. They also suggested that transverse breakage of mineral fibres depends on their diameter, not on physical type.
• Limitations the authors state:
  • Because of the electron microscope's resolution, fibre size measurements were limited to fibres with diameters greater than 0.2 um.
  • Data were available for only five of the plants. Whether glass wool and rock wool fibres really differ needs further investigation when data for more plants become available.

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