Exposure to refractory ceramic fibres in the metal industry

Our plain-English summary of Exposure to refractory ceramic fibres in the metal industry, by M. Linnainmaa, J. Kangas, M. Mäkinen, et al (The Annals of Occupational Hygiene, 2007).

The study

• Authors: M. Linnainmaa, J. Kangas, M. Mäkinen, S. Metsärinne, A. Tossavainen, J. Säntti, M. Veteli, H. Savolainen, P. Kalliokoski
• Journal: The Annals of Occupational Hygiene
• Published: 2007;51(6):509-16
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Refractory ceramic fibres (RCF) are used in thermal isolation in the metal industry where high temperatures are regularly employed. Asbestos materials were earlier commonly used for these purposes. In this work, two Finnish steel plants, three foundries and a repair shop were studied for the ceramic fibre exposure of their workers under normal production and during the replacement of oven insulation. Personal and stationary sampling was used together with a novel nasal lavage sampling for the evaluation of personal exposure. Fibres were counted with optical and electron microscopy and they were identified using an energy-dispersive X-ray analyser. Ceramic fibres were found in most production phases [range <0.01-0.29 fibres per cubic centimetre (f cm(-3))]. Considerably higher fibre counts were obtained during the maintenance work (range <0.01-14.2 f cm(-3)). Nasal sampling was found to correlate with the airborne fibre concentrations at the group level. The mean fibre concentrations varied from 34 to 6680 f ml(-1) of lavage liquid. Use of personal respiratory protectors diminished the exposure on the average as analysed in the lavage specimens, but the effect of respirator use did not appear clearly in the results. Because of the heat conditions, the workers used the respirators for a strict minimum period. A considerable exposure to RCF occurs in the studied plants. Its risk should be evaluated and managed more closely in view that the material is carcinogenic. Use of personal respiratory protectors should be encouraged. Their effective use could be verified by the nasal sampling for fibres after the work shift.

In plain English

This study measured workers' exposure to refractory ceramic fibres (RCF), a heat insulation material. Asbestos, which was used earlier for this purpose, was not measured. In 2004–2005 the researchers sampled air at fixed points and from the breathing zones of 55 workers in two Finnish steel plants, three foundries and a repair shop. They also counted fibres in nose rinses (nasal lavage). During normal production, ceramic fibre levels ranged from below 0.01 to 0.29 fibres per cubic centimetre. During maintenance breaks, levels were far higher. In electron-microscopy personal samples, mean RCF was 1.35 fibres per cubic centimetre in Plant A (removal and installation of furnace insulation) and 4.49 in Plant B (removal), with Plant B's highest sample at 14.20. In the repair shop, every personal sample exceeded the exposure limit of 0.2 fibres per cubic centimetre. Foundry levels were lower. Nasal counts tracked air levels for groups but not for individuals. Respirators lowered nasal counts on average, but the effect was not clear in the results. The authors concluded that workers handling RCF are exposed, mainly because of deficient respirator use.

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: Workplace exposure measurement study using personal and fixed-location air sampling plus nasal lavage sampling
• Who was studied: Workers at two steel plants, three foundries (iron, steel, copper) and a repair shop in Finland. Breathing-zone samples came from 55 workers. Measurements were made in 2004–2005.
• Exposure: Refractory ceramic fibres (RCF) and man-made mineral fibres (MMMF) from thermal insulation, during normal production and during removal and installation of furnace (oven) insulation
• Main results:
  • During normal production, ceramic fibres were found in most production phases, ranging from below 0.01 to 0.29 fibres per cubic centimetre
  • Steel plant A, removal and installation of furnace insulation (combined) during the maintenance break, personal samples (8 samples): mean RCF by electron microscopy 1.35 fibres per cubic centimetre, range 0.14 to 4.20
  • Steel plant B, removal of furnace insulation during the maintenance break, personal samples (6 samples): mean RCF by electron microscopy 4.49 fibres per cubic centimetre, range 1.07 to 14.20
  • Repair shop: fibre levels exceeded the limit of 0.2 fibres per cubic centimetre in all personal samples, and virtually all airborne fibres there were RCF
  • Foundries (normal production only): exposure was lower than in the steel plants, and no excessive exposure levels were detected
  • Inhalable dust levels did not correlate with fibre levels
  • Nasal lavage during normal production: mean fibre levels were 55 to 430 fibres per ml in steel Plant A and 34 to 930 in Plant B. Neither respirator use nor respirator type had a clear effect on these levels.
  • Nasal lavage levels were clearly higher in the service shop and during steel plant service breaks, even though respirators were generally worn
  • Foundry nasal lavage samples were generally low (16 to 314 fibres per ml, 15 samples). Two workers had exceptionally high levels (2660 and 10 700 fibres per ml). None of the foundry workers wore a respirator.
  • Nasal lavage results followed airborne fibre levels at the group level, but the correlation was not good for individual workers
  • Respirator use reduced exposure on average, as measured in the nasal lavage samples, but the effect of respirator use did not appear clearly in the results
• The authors' conclusion: The authors concluded that workers handling RCF are exposed to fibres, especially in the steel industry and among its maintenance subcontractors, mainly because of deficiencies in respirator use
• Limitations the authors state:
  • Nasal lavage has inherent problems: fibres may accumulate in the nostrils, and fibres may be removed when workers blow their noses during the day
  • Only fibres longer than 20 micrometres were counted in the nasal lavage samples
  • Optical microscopy may have missed some thin fibres

Topics

Medical terms in this study, explained in our Lexicon: Respirator, Carcinogenic.

Related studies

• Potential significance of airborne fiber dimensions measured in the U.S. refractory ceramic fiber manufacturing industry — T.J. Lentz, C.H. Rice, et al. (1999)
• Are airborne refractory ceramic fibers similar to asbestos in their carcinogenicity? — A.M. Walker, L.D. Maxim, et al. (2012)
• Refractory ceramic fibers: Fiber characteristics, potential health effects and clinical observations — M.J. Utell, L.D. Maxim (2018)
• Clinico-pathological features and somatic gene alterations in refractory ceramic fibre-induced murine mesothelioma reveal mineral fibre-induced mesothelioma identities — P. Andujar, C. Lecomte, et al. (2007)
• Pseudoasbestos bodies and fibers in bronchoalveolar lavage of refractory ceramic fiber users — P. Dumortier, I. Broucke, et al. (2001)
• Perspectives on refractory ceramic fiber (RCF) carcinogenicity: comparisons with other fibers — H. Greim, M.J. Utell, et al. (2014)

Browse more research in The Annals of Occupational Hygiene, or return to medical research.