Some biological properties of respirable iron ore dust

Our plain-English summary of Some biological properties of respirable iron ore dust, by D. Keast, N.P. Sheppard, J.M. Papadimitriou (Environmental Research, 1987).

The study

• Authors: D. Keast, N.P. Sheppard, J.M. Papadimitriou
• Journal: Environmental Research
• Published: 1987;42(2):455-68
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The respirable fraction of an ore dust from the North-West of Western Australia was tested for biological properties by inhalation and intrapleural implantation trials using rats and mice. Pulmonary histology indicated significant levels of interstitial pneumonia occasionally associated with bronchopneumonia, bronchiectasis, emphysema, and lung collapse over that found in age-matched control animals. While there was a significant increase of the incidence of tumors in general in WAG inbred rats up to 2 years following dust exposure, this did not persist into old age. No mesotheliomas were induced by any treatments associated with iron ore dust, although the rats were shown to be susceptible to crocidolite asbestos-induced mesothelioma. In the mouse models, tumors which are normally seen only in aged animals were induced with a significant number of bronchial adenomas being recorded following intrapleural implantation of dust into inbred BALB/c mice. Leukemia/lymphoma associated with murine leukemia virus was increased following dust inhalation by inbred C57BL mice.

In plain English

This was an animal experiment from Western Australia. It tested the respirable (breathable) fraction of dust from an iron ore mine in the North-West of the state. Analysis of the dust found fibrous particles, but none could be classified as asbestos. Female rats and mice breathed air containing 5.7 to 12.3 milligrams of dust per cubic metre for 4 hours a day, 5 days a week. Others had the dust placed in the chest cavity (intrapleural implantation). Some rats received crocidolite asbestos implants for comparison. Interstitial pneumonia was more severe in dust-exposed rats than in unexposed controls. No mesotheliomas occurred with the iron ore dust, while 25% of the crocidolite-implanted rats developed mesothelioma. In rats that breathed the dust, overall tumor rates were significantly raised before 2 years of age but not in old age. Mice that breathed the dust had more lymphoma/leukemia after 3 months and lifetime exposure, and more murine leukemia virus. Implanted BALB/c mice had more lung adenomas. The authors concluded that the dust was associated with an increase in interstitial pneumonia and other lung lesions.

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: Animal experiment (inhalation and intrapleural implantation trials in rats and mice)
• Who was studied: Laboratory animals at the University of Western Australia. About 200 female inbred WAG rats and 300 female inbred C57BL/6J mice were exposed by inhalation. For implantation, 76 female WAG rats received iron ore dust and 20 received crocidolite asbestos, and BALB/c mice received dust (431 test animals and 371 controls). Unexposed age-matched controls were used throughout.
• Exposure: Respirable fraction of iron ore dust from an open cut mine in the North-West of Western Australia. Inhalation was at 5.7 to 12.3 mg/m3 for 4 hours a day, 5 days a week. Implants were 50 mg of dust for rats and 20 mg for mice. A comparison group of rats received 20 mg of crocidolite asbestos by implant.
• Main results:
  • In 91 analysed samples of the respirable dust, none of the fibers could be classified as asbestos; they were aluminosilicate or iron rich.
  • In rats that inhaled the dust, interstitial pneumonia was generally more severe than in age-matched controls, and it increased with the level of exposure.
  • Pyelonephritis and pyonephrosis were more common in dust-inhaling rats than in controls: 47% versus 23.4%, P < 0.01.
  • In rats that inhaled the dust, the overall incidence of tumors was significantly raised before 2 years of age, and this did not persist into old age. Table 5 gives 21.0% in dust-exposed rats versus 10.4% in controls under 24 months (significance 0.05). Over 24 months it gives 22.4% versus 16.1% (not significant). No particular tumor type appeared to be induced consistently.
  • No mesotheliomas occurred after inhalation or intrapleural implantation of the iron ore dust, or in controls.
  • In rats implanted with crocidolite asbestos, 25% developed mesotheliomas. The first appeared at 18 months.
  • In rats implanted with iron ore dust, total tumors up to 21 months of age were significantly higher than in controls (P < 0.001). By the end of the natural life span there were no significant differences overall.
  • In C57BL mice that inhaled the dust, lymphoma/leukemia was significantly more frequent after 3 months of exposure: 18.7% (6 of 32) versus 6.2% (2 of 32) of controls. It was also more frequent after lifetime exposure: 9.5% (5 of 52) versus 2.0% (1 of 51) of controls.
  • Murine leukemia virus was found in both dust-exposed and control C57BL mice. Significantly more virus was detected in dust-exposed mice (P < 0.01).
  • In BALB/c mice with intrapleural dust implants, lung (bronchial) adenomas were significantly increased over the period 13 to 21 months after implantation. At 21 months the rate was 47.3% versus 21.4% in controls. At 24 months it was 23.8% versus 29.8%, which was not significant.
  • In implanted BALB/c mice up to 18 months of age, leukemia/lymphoma incidence was 2.58% in dust-implanted animals and 1.86% in controls. This difference was not significant.
• The authors' conclusion: The authors concluded that, in both rat and mouse inhalation and implantation models, the respirable iron ore dust was associated with an increase in interstitial pneumonia and other pulmonary lesions. They also stated that no mesotheliomas were induced by the dust.
• Limitations the authors state:
  • About 1% of animals died from an undiagnosed, possibly mycoplasmal, lung infection.
  • In the BALB/c implant trial, 16 dust-implanted and 12 control mice could not be assessed because of cannibalism.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Crocidolite.

Medical terms in this study, explained in our Lexicon: Respirable Fraction, Histology, Interstitial, Emphysema, Mesothelioma, Crocidolite.

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• Biological activity of respirable industrial fibres treated to mimic residence in the lung — K. Donaldson (1994)
• Dust particles in lung sections. Some notes on methods of their visualization — P. Gross, E.B. Tolker (1966)
• Enhanced generation of free radicals from phagocytes induced by mineral dusts — V. Vallyathan, J.F. Mega, et al. (1992)

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