Asbestos fibers and trace metals in the blood of cattle grazing in fields inundated by asbestos-rich sediments

Our plain-English summary of Asbestos fibers and trace metals in the blood of cattle grazing in fields inundated by asbestos-rich sediments, by H. Schreier, J.A. Shelford, T.D. Nguyen (Environmental Research, 1986).

The study

• Authors: H. Schreier, J.A. Shelford, T.D. Nguyen
• Journal: Environmental Research
• Published: 1986;41(1):99-109
• Read it: PubMed · Publisher

Abstract

During a major storm in 1975, a pasture was inundated with serpentinitic sediments which are rich in asbestos fibers and trace metals. Little natural revegetation has occurred at the site and dairy and beef cattle which continue to graze in and around the contaminated site are exposed to asbestos fibers by inhalation and ingestion. The effect of this material on the cattle was investigated in this study by analyzing blood samples from exposed and control animals for asbestos fibers, trace metals, and general blood chemistry. The analysis showed that at the time of exposure Ni and Mn values were significantly higher in the exposed animals than in the controls, and in six out of seven samples asbestos fibers were present as determined by STEM analysis. Once the animals were removed from the site, trace metal levels returned to normal but asbestos fibers were still present in three out of seven animals. Two of the control animals unaffected by the sediments also showed asbestos fibers and there were no relationships between the magnitude of fibers and trace metal content. This suggests that the sediments influence the blood chemistry of animals but the presence and magnitude of asbestos fibers in the blood can be influenced by other factors as well.

In plain English

This study looked at cattle on a farm near Everson, Washington, where a 1975 flood covered a pasture of about 4 hectares with serpentinitic sediments. The authors found these sediments to be rich in chrysotile asbestos. Blood was taken from exposed animals in August 1983, while they were grazing at the site, and again in November 1983, several weeks after they had been moved off it. Control animals came mostly from a university farm in British Columbia. In August, six of seven exposed animals' samples contained chrysotile fibers, at 5 x 10^4 to 1 x 10^6 fibers per liter of blood. In November three of seven did, and so did two of five control samples. Fiber levels did not rise with exposure, and control levels were not significantly different from August levels. Blood nickel and manganese were significantly higher in August and returned to normal by November. Fiber counts were not related to metal levels. The authors concluded that exposed animals had fibers in their blood. However, they did not have enough evidence that exposure led to higher fiber levels, and they noted mixed breeds and uncertain exposure lengths.

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: Field study comparing blood samples from exposed and control cattle, taken at two time points
• Who was studied: Mixed-breed dairy and beef cattle at a farm in Everson, Washington, near the Sumas River. Twelve potentially exposed animals were available, and seven exposed animals' samples are reported at each sampling. Controls were six animals from the University of British Columbia farm plus one calf brought to the farm a few days before sampling. Sampling dates were August 30 and November 7, 1983.
• Exposure: Grazing on and near a pasture covered in 1975 by serpentinitic flood sediments containing chrysotile asbestos and trace metals (nickel, chromium, manganese, cobalt). Exposure was by inhalation and ingestion.
• Main results:
  • In the exposed animals' August samples (taken during grazing), trace metal levels were significantly higher than in the November samples or the control samples.
  • Six of seven August samples from exposed animals contained asbestos fibers, at 5 x 10^4 to 1 x 10^6 fibers per liter of blood.
  • Three of seven November samples from exposed animals contained fibers.
  • Two of five control samples (40%) contained fibers.
  • The fibers found in blood were identified as chrysotile asbestos.
  • Fiber concentration did not increase with exposure. The control samples' fiber levels were not significantly different from those of the August samples.
  • The authors reported not having enough evidence that exposure to the sediments leads to higher blood asbestos fiber levels.
  • No positive relationship was found between trace metal concentrations and the number of asbestos fibers in the blood.
  • General blood chemistry did not differ significantly between the exposed animals' August samples and the control samples.
  • The exposed animals' November samples showed significantly higher hemoglobin and hemoglobin iron than the controls, and slightly lower phosphate.
  • Aspartate aminotransferase (SGOT) was high compared with literature standards in all samples, including the controls.
• The authors' conclusion: The authors concluded that grazing animals exposed to the asbestos-rich sediments had detectable asbestos fibers in their blood at the time of exposure. They found that nickel and manganese levels were above normal during exposure and returned to normal after removal. They concluded that no quantitative trend was found between fiber concentration and exposure.
• Limitations the authors state:
  • Only one animal had been near the pasture for the full 8 years since the flood.
  • The other animals' length of exposure was variable and uncertain.
  • None of the animals were purebred; all were mixed breeds.
  • The authors noted that background contamination is a common problem in asbestos counting, though they judged contamination of the control samples unlikely.
  • All animals, including controls, were also exposed to asbestos fibers in their drinking water.
  • The authors suggested the fiber counting method may not be sensitive enough to show a dose-response relationship.
  • The authors suggested the animal group was too varied, which may have masked results.

Topics

Medical terms in this study, explained in our Lexicon: STEM.

Related studies

• Some observations on the distribution of trace metals in chrysotile asbestos — A. Morgan, A.E. Lally, et al. (1973)
• Asbestos fibres introduce trace metals into streamwater and sediments — H. Schreier (1987)
• Translocation and bioaccumulation of metals in Oryza sativa and Zea mays growing in chromite-asbestos contaminated agricultural fields, Jharkhand, India — A. Kumar, S.K. Maiti (2014)
• Health effects of natural dust: role of trace elements and compounds — A.G. Cook, P. Weinstein, et al. (2005)
• Major and trace element compositions of the UICC standard asbestos samples — D.R. Bowes, C.M. Farrow (1997)
• Concentrations of asbestos fibers and metals in drinking water caused by natural crocidolite asbestos in the soil from a rural area — B. Wei, B. Ye, et al. (2013)

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