Formation of hydroxyl radicals and toxicity of tungsten oxide fibres

Our plain-English summary of Formation of hydroxyl radicals and toxicity of tungsten oxide fibres, by P. Leanderson, W. Sahle (Toxicology in Vitro, 1995).

The study

• Authors: P. Leanderson, W. Sahle
• Journal: Toxicology in Vitro
• Published: 1995;9(2):175-83
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Occupational exposure to hard metal dust may cause interstitial pulmonary fibrosis and asthma. The cause of asthma is well established, whereas the cause of lung fibrosis is still under debate. Recently, slightly reduced airborne tunsten oxide fibres, the role of which in hard metal pneumoconiosis has never been accounted for, were detected in an air sample from a hard metal production plant. In this study, the capacity to generate hydroxyl radicals, toxicity to cultured human lung cells and haemolytic activity of tungsten oxide fibres were compared with crocidolite asbestos fibres. The results show (a) that tungsten oxide fibres can generate hydroxyl radicals, and (b) that tunsten oxide fibres were more cytotoxic to human lung cells than was crocidolite, but (c) that the haemolytic activity of tungsten oxide fibres was lower than for crocidolite.

In plain English

This was a laboratory study from Sweden of tungsten oxide fibres. The authors noted these fibres had recently been found in dust from a hard metal industry. The authors made tungsten oxide fibres in the laboratory and compared them with standard (UICC) crocidolite and anthophyllite asbestos samples. They measured how much each fibre type produced hydroxyl radicals, a reactive form of oxygen. They also compared tungsten oxide with crocidolite for damage to cultured human bronchiolar (airway) cells over 48 hours and to human red blood cells over 1 hour. The radical marker was roughly 17 times the level in unexposed controls for crocidolite, 10 times for tungsten oxide and three times for anthophyllite. Release of a cell-damage marker rose from 25% in unexposed cells to 31, 35 and 64% at increasing doses of tungsten oxide fibres, and to 33, 31 and 42% at the same doses of crocidolite. Crocidolite caused about five times more red blood cell damage than tungsten oxide. The authors concluded that tungsten oxide fibres can form hydroxyl radicals and are toxic to human lung cells. They suggested re-examining existing data on hard metal 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: In vitro laboratory experiment (cell-free chemical tests, cultured human lung cells, human red blood cells)
• Who was studied: Cultured human bronchiolar cells (cell line 14 Br), and red blood cells from venous blood of healthy human donors; no workers were studied
• Exposure: Laboratory-synthesized tungsten oxide fibres, compared with UICC standard crocidolite and anthophyllite asbestos. Cell doses were 10, 50 or 200 micrograms of fibre per square centimetre for 48 hours. Radical tests used 0.2 to 5 mg fibre per ml for 1 hour.
• Main results:
  • After 1 hour, the hydroxyl radical marker (8-hydroxydeoxyguanosine) in anthophyllite samples was approximately three times the level in unexposed controls. The corresponding figures were 10 times for tungsten oxide and 17 times for crocidolite.
  • Adding catalase (an enzyme that breaks down hydrogen peroxide) substantially reduced radical formation in the crocidolite and tungsten oxide samples. It had no effect in the anthophyllite samples.
  • In cultured human lung cells, release of the cell-damage marker (chromium-51) was 25% in the control sample without fibres. At 10, 50 and 200 micrograms per square centimetre, release was 31, 35 and 64% for tungsten oxide fibres and 33, 31 and 42% for crocidolite.
  • Crocidolite caused about five times more damage (haemolysis) to human red blood cells than tungsten oxide fibres.
• The authors' conclusion: The authors concluded that their in vitro study suggests tungsten oxide fibres can form hydroxyl radicals and are toxic to human lung cells. They considered it possible that these fibres contribute to pneumoconiosis among hard metal workers, and suggested re-examining existing epidemiological data on hard metal workers.
• Limitations the authors state:
  • The authors noted that red blood cell damage does not necessarily correlate with a dust's ability to cause fibrosis, so it cannot be used as a short-term test of that effect.
  • The authors noted that the study did not examine how tungsten oxide fibres affect inflammatory cells, which may also damage the lung, and said this should be investigated.

Topics

Medical terms in this study, explained in our Lexicon: Hydroxyl Radical, Occupational Exposure, Interstitial, Pulmonary Fibrosis, Fibrosis, Pneumoconiosis, Crocidolite.

Related studies

• Fiber-induced hydroxyl radical formation: correlation with mesothelioma induction in rats and humans — K.R. Maples, N.F. Johnson (1992)
• Identifying the reactive sites of hydrogen peroxide decomposition and hydroxyl radical formation on chrysotile asbestos surfaces — M. Walter, W.D.C. Schenkeveld, et al. (2020)
• Hydroxyl radical production in the presence of fibres by a Fenton-type reaction — M. Gulumian, J.A. van Wyk (1987)
• Asbestos catalyzes hydroxyl and superoxide radical generation from hydrogen peroxide — S.A. Weitzman, P. Graceffa (1984)
• Role of oxidants in DNA damage. Hydroxyl radical mediates the synergistic DNA damaging effects of asbestos and cigarette smoke — J.H. Jackson, I.U. Schraufstatter, et al. (1987)
• Hydroxyl radicals are formed in the rat lung after asbestos instillation in vivo — R.M. Schapira, A.J. Ghio, et al. (1994)

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