Exposure to metals in the manufacture of asbestos textile products

Our plain-English summary of Exposure to metals in the manufacture of asbestos textile products, by L.J. Cralley, R.G. Keenan, J.R. Lynch (American Industrial Hygiene Association Journal, 1967).

The study

• Authors: L.J. Cralley, R.G. Keenan, J.R. Lynch
• Journal: American Industrial Hygiene Association Journal
• Published: 1967;28(5):452-61
• Cited by: 25 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 002528).

In plain English

This 1967 study measured nickel, chromium, cobalt and manganese in asbestos textile manufacturing. It did not examine workers' health. Mine-milled Canadian chrysotile averaged 0.10% nickel, and African chrysotile had about 50 to 100% more nickel and chromium. Metals were concentrated in the smaller size fraction of milled asbestos, and adjoining serpentine rock held 10 times the nickel of cleaned fiber. In a ventilation-off test run at one plant, imitating 1930s practice, airborne dust carried more metal than the bulk fiber. At carding, for example, it held 2.7 times the nickel. The authors identified wear on metal processing equipment as a second source. In seven plants in 1961-65, average airborne nickel ranged from 0.72 micrograms per cubic meter at weaving to 8.14 at twisting. The authors estimated pre-1930-35 carding levels at 330 micrograms of nickel per cubic meter, using a method they said had many limitations. Laboratory grinding added metal from the mills to chrysotile. The authors concluded that the role of metals in asbestos-related disease should not be ignored, while stating that their significance was not clear.

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: Industrial hygiene exposure study (preliminary report). It combined chemical analysis of asbestos fiber and ore samples, a special test run in one asbestos textile plant with ventilation off, air sampling in seven plants, estimation of past exposures, and a laboratory grinding experiment. No workers' health outcomes were studied.
• Who was studied: No human subjects. The study used samples of mine-milled Canadian and African chrysotile, crocidolite and amosite fibers, and chrysotile ore zones; a special test run in one cooperating asbestos textile plant; and airborne dust samples from seven asbestos textile plants, 1961-65.
• Exposure: Nickel, chromium, cobalt and manganese in asbestos fiber (mainly chrysotile), in airborne dust at textile operations (fiber preparation, carding, spinning, twisting, weaving), and in the metal alloys of processing equipment
• Main results:
  • In Canadian chrysotile, nickel ranged from 0.01 to 0.20% with an average of 0.10%.
  • Nickel and chromium were around 50 to 100% greater in African chrysotile than in Canadian chrysotile.
  • Compared with chrysotile, manganese was 50% lower in crocidolite and around twentyfold higher in amosite.
  • For two chrysotile grades, the smaller size fraction (under 200 mesh) had appreciably more metal than the larger fraction.
  • Nickel in the adjoining serpentine wall rock (1815 micrograms per gram) and in its magnetic concentrate (2125 micrograms per gram) was 10 and 11 times higher, respectively, than in the cleaned fiber.
  • In the special test run (ventilation off), the ratio of metal in airborne dust to metal in bulk fiber at carding was 2.7 to 1.0 for nickel, 4.2 to 1.0 for chromium, no difference for cobalt, and 2.3 to 1.0 for manganese.
  • The authors concluded that abrasion of processing equipment by asbestos was a supplementary source of airborne metal.
  • In seven textile plants (1961-65), average airborne nickel ranged from 0.72 micrograms per cubic meter at weaving to 8.14 micrograms per cubic meter at twisting.
  • Estimated pre-1930-35 levels at carding were 330 micrograms per cubic meter for nickel, 250 for chromium and 120 for manganese.
  • Estimated pre-1930-35 exposures to the total metals were greater than current levels by a conservative factor of 270 at fiber preparation and 140 at carding.
  • Grinding chrysotile in a hammer mill raised its chromium content 3.5 to 4.0 times. The authors concluded that the asbestos abraded the metal of the mill.
• The authors' conclusion: The authors concluded that their evidence indicated the role of metals in disease associated with asbestos inhalation should not be ignored.
• Limitations the authors state:
  • The method used to estimate past exposures had many limitations.
  • The crocidolite and amosite values came from a limited number of samples.
  • The 1961-65 plant data were limited samples that did not cover all types of processing.
  • The weaving test produced little dust and may not have represented weaving in the mid-1930s.
  • How the metals were distributed between respirable grains and fibers was unknown.
  • The report gave only preliminary findings for four metals.
  • The significance of these metals in past exposures was not clear.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestos textiles, Asbestosis.

Related studies

• Health progress in an asbestos textile works — J. Mitchell (1961)
• Technological feasibility of the 2 fibers/cc asbestos standard in asbestos textile facilities — R.A. Curtis, P.H. Bierbaum (1975)
• Metal interactions in carcinogenesis: enhancement, inhibition — G.F. Nordberg, O. Andersen (1981)
• Occurrence of heavy metal-resistance in microflora from serpentine soil of Andaman — A. Pal, S. Dutta, et al. (2005)
• Asbestos and metals as carcinogens — T. Norseth (1980)
• Metallic elements in crude and milled chrysotile asbestos from Quebec — C. Barbeau, M. Dupuis, et al. (1985)

Browse more research in American Industrial Hygiene Association Journal, or return to medical research.