Environmental exposure to asbestos and other inorganic fibres using animal lung model

Our plain-English summary of Environmental exposure to asbestos and other inorganic fibres using animal lung model, by E. Fornero, E. Belluso, S. Capella, et al (The Science of the Total Environment, 2009).

The study

• Authors: E. Fornero, E. Belluso, S. Capella, D. Bellis
• Journal: The Science of the Total Environment
• Published: 2009;407(3):1010-8
• Cited by: 15 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Professional exposure to asbestos fibres is widely recognized as very dangerous to human health and for this reason many countries have banned their commercial uses. People, nevertheless, continue to be exposed to low dose of asbestos from natural and anthropogenic sources still in loco, for which the potential hazard is unknown. The aim of this research is to assess environmental exposure in an area with outcropping serpentinite rocks, which bear asbestos mineralizations, using sentinel animals which are a non-experimental animal model. We studied the burden of inorganic fibres in cattle lungs which come from two areas in Italy's Western Alps bearing serpentinitic outcrops: Susa Valley with a heavy anthropization and Lanzo Valleys, with a minor human impact. The identification and quantification of inorganic fibres were performed by Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer (EDS). In comparison to humans, studies of animals have some advantages, such as no occupational exposure or history of smoking and, in the case of cattle, a sedentary life restricted to one region. Results spotlight that over than 35% of inorganic fibres found both in Susa and Lanzo valleys, belong to asbestos mineralogical species (asbestos tremolite/actinolite, chrysotile s.s., asbestos grunerite, crocidolite). We also observed a higher concentration of artificial fibrous products in Susa samples showing a correlation with the level of anthropization. These results confirm that sentinel animals are an excellent model to assess breathable environmental background because it is possible to eliminate some variables, such as unknown occupational exposure.

In plain English

The authors used cattle as "sentinel animals" to gauge background levels of breathable fibres in two valleys of Italy's Western Alps where serpentinite rocks bearing asbestos reach the surface: the more industrialized Susa Valley and the less developed Lanzo Valleys. They examined lung tissue from 39 cattle (20 from Susa, 19 from Lanzo) by light and electron microscopy. Asbestos bodies appeared in only 7 lungs, all below 100 per gram of dry lung, under the level of 1000 usually taken to indicate occupational exposure. Asbestos fibres were found in 29 of the 39 lungs and made up 36% of all fibres in Susa and 37% in Lanzo. Asbestos tremolite/actinolite, which the authors attribute to natural rock, was the most common asbestos in both valleys. Crocidolite and asbestos grunerite, attributed to man-made sources, were found in only 3 lungs. Artificial fibrous products made up 45% of fibres in Susa versus 20% in Lanzo. The authors concluded that people living in these areas have a significant local environmental exposure. They noted that the small number of samples did not allow them to relate fibre burden to the animals' age.

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: Environmental study using sentinel animals (a non-experimental animal model): analysis of mineral fibre burden in cattle lung tissue
• Who was studied: Lung samples from 39 cattle, 20 from Susa Valley and 19 from Lanzo Valleys (Piedmont Region, north-western Italy), taken from 21 localities. All were female except two males from Susa. Average age was 6 years (range 2 to 15) in Susa and 9 years (range 3 to 16) in Lanzo. Samples were taken from the right lower lobe.
• Exposure: Environmental (non-occupational) exposure to airborne inorganic fibres, including asbestos, in two areas with outcropping serpentinite rocks. Susa Valley was described as heavily anthropized and Lanzo Valleys as having minor human impact. Asbestos bodies were counted by optical microscopy, and fibres were identified and counted by scanning electron microscopy with energy dispersive spectrometry.
• Main results:
  • Asbestos bodies were found in only 7 of the 39 samples (4 from Susa, 3 from Lanzo). In all samples their concentration was below 100 asbestos bodies per gram of dry lung, well under the 1000 per gram usually considered indicative of occupational exposure.
  • Asbestos fibres were found in 29 of the 39 lung samples: 14 from Susa Valley and 15 from Lanzo Valleys.
  • Average total inorganic fibre concentrations were similar: 100,347 fibres per gram of dry lung in Susa Valley cattle and 92,626 in Lanzo Valleys cattle.
  • Asbestos made up 36% of total fibres in Susa samples (average 36,623 asbestos fibres per gram of dry lung) and 37% in Lanzo samples (average 34,543 per gram).
  • Asbestos tremolite/actinolite was always the most abundant asbestos, with average concentrations of 32,076 fibres per gram of dry lung in Susa samples and 32,667 in Lanzo samples.
  • Asbestos the authors attributed to anthropogenic (man-made) sources was detected in only 3 samples (2 from Susa, 1 from Lanzo). Asbestos grunerite was found in both valleys; crocidolite was found only in Susa Valley.
  • Fibres of chrysotile s.s. were almost absent in both valleys.
  • Artificial fibrous products (TiO2, silicatic man-made, Fe–Cr rich) made up 45% of fibres in Susa samples and 20% in Lanzo samples. Fibrous serpentine made up 21% in Lanzo and 3% in Susa.
  • Natural-source tremolite/actinolite (asbestos and non-asbestos combined) averaged 0.01 million fibres per gram of dry lung in Upper Susa Valley and in Lower Lanzo Valleys. It averaged 0.06 million in Lower Susa Valley and 0.13 million in Upper Lanzo Valleys, the areas where the authors say outcropping rocks are more widespread.
  • Most fibres fell within the breathable fibre definition (84% in Susa, 82% in Lanzo). One Susa fibre and no Lanzo fibres met Stanton's definition of a carcinogenic fibre.
• The authors' conclusion: The authors concluded that the results show a significant local environmental exposure for the human population living in the studied areas. They also concluded that sentinel animals are an excellent model for assessing the breathable environmental background, because variables such as unknown occupational exposure can be eliminated.
• Limitations the authors state:
  • The limited number of samples did not allow a correlation between the animals' age and inorganic fibre burden.
  • Older animals would better simulate human exposure, but cattle are slaughtered young for commercial reasons.
  • Tremolite and actinolite could not be told apart chemically by the analysis method and were grouped together.
  • Chrysotile and antigorite were hard to distinguish, so some fibres were grouped as "fibrous serpentine".
  • The comparison studies (Corsican goats, California pets) were not done under the same research conditions.
  • The authors could not explain why one Lanzo sample (VL09) had no inorganic fibres.

Topics

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

Medical terms in this study, explained in our Lexicon: Environmental Exposure, Serpentinite, Susa Valley, Occupational Exposure, Tremolite, Actinolite, Chrysotile, Grunerite.

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