The wild rat as sentinel animal in the environmental risk assessment of asbestos pollution: a pilot study

Our plain-English summary of The wild rat as sentinel animal in the environmental risk assessment of asbestos pollution: a pilot study, by M. Ardizzone, C. Vizio, E. Bozzetta, et al (The Science of the Total Environment, 2014).

The study

• Authors: M. Ardizzone, C. Vizio, E. Bozzetta, M. Pezzolato, S. Meistro, A. Dondo, I. Giorgi, A. Seghesio, D. Mirabelli, S. Capella, R. Vigliaturo, E. Belluso
• Journal: The Science of the Total Environment
• Published: 2014;479-480:31-8
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Asbestos has been banned in many countries, including Italy. However, sources of exposure may still exist, due to asbestos in-situ or past disposal of asbestos-containing waste. In an urban area with past high environmental exposure, like Casale Monferrato, the lung fiber burden in sentinel animals may be useful to identify such sources. A pilot study was conducted to assess the feasibility of its determination in wild rats, a suitable sentinel species never used before for environmental lung asbestos fiber burden studies. Within the framework of pest control campaigns, 11 adult animals from 3 sites in the urban area of Casale Monferrato and 3 control rats from a different, unexposed town were captured. Further, 3 positive and 3 negative control lung samples were obtained from laboratories involved in breeding programs and conducting experimental studies on rats. Tissue fiber concentration was measured by scanning electron microscopy with energy dispersive spectrometry. Asbestos (chrysotile and crocidolite) was identified in the lungs from rats from Casale Monferrato, but not in control rats and in negative control lung samples. Asbestos grunerite at high concentration was found in positive control lung samples. Measurement of the lung fiber burden in wild rats has proved feasible: it was possible not only to detect, but also to characterize asbestos fibers both qualitatively and quantitatively. The pilot study provides the rationale for using wild rats as sentinels of the soil contamination level in Casale Monferrato, to identify areas with the possible presence of previously unrecognized asbestos sources.

Copyright © 2014 Elsevier B.V. All rights reserved.

In plain English

This pilot study tested whether asbestos fibers could be measured in wild rats' lungs in Casale Monferrato, Italy, so rats could serve as sentinels for soil contamination. The authors examined lungs from 11 wild rats caught at three sites there, 3 wild rats from Asti, a town with no major asbestos company, 3 unexposed laboratory rats and 3 that had inhaled asbestos grunerite for 3 months. Fibers were identified by scanning electron microscopy with energy dispersive spectrometry, matching their chemical spectra to a reference database. Chrysotile was found in five Casale Monferrato rats, and crocidolite in three rats from two sites. Tremolite/actinolite asbestos was found in some Casale Monferrato and Asti rats. The unexposed laboratory rats had no inorganic fibers. Grunerite in the exposed laboratory rats was reported as three orders of magnitude higher than in wild rats. The authors concluded that measuring lung fiber burden in wild rats was feasible and supported using them as sentinels. They noted that not every rat from an area had detectable asbestos, so more than one rat per area is needed.

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: Pilot feasibility study measuring lung fiber burden in wild rats, compared with laboratory rats used as positive and negative controls (necropsy, PCR, histology, SEM-EDS)
• Who was studied: Lungs from 20 rats. There were 11 wild rats from three sites in Casale Monferrato (the group of interest) and 3 wild rats from Asti (environmental control), all captured during municipal rodent control programs. There were also 3 Sprague Dawley laboratory rats from Charles River Italy (negative controls) and 3 Fischer 344 laboratory rats from the Hannover Fraunhofer Institute (positive controls).
• Exposure: Environmental exposure of wild rats in Casale Monferrato, compared with Asti, where no major asbestos company or asbestos-using company had operated. Positive-control laboratory rats had inhaled asbestos grunerite for 3 months in an earlier subchronic inhalation study. Fibers measured included chrysotile, crocidolite, grunerite asbestos, tremolite/actinolite asbestos and non-asbestos inorganic fibers.
• Main results:
  • Fibers were identified by comparing their energy dispersive spectrometry (EDS) spectra with a database built by two of the authors.
  • Crocidolite was found in the lungs of three Casale Monferrato rats from two sites, at 4541 to 4634 breathable fibers per gram of dry weight (Table 2).
  • Chrysotile was the most frequent and abundant asbestos in the wild rat lungs. It was found in five Casale Monferrato samples, at 4634 to 23,170 fibers per gram of dry weight (Table 2).
  • Tremolite/actinolite asbestos was found in three Casale Monferrato samples.
  • Rats from Asti showed only tremolite/actinolite asbestos, in amounts similar to some Casale Monferrato sites. Table 2 lists 10,928 fibers per gram of dry weight for rat AT/01.
  • Positive-control rats (grunerite-exposed) had a high grunerite asbestos content: 100,189,669 to 110,565,298 breathable fibers per gram of dry weight in Table 2. The authors described this as three orders of magnitude higher than in the wild rats.
  • Negative-control laboratory rats contained no inorganic fibers of any kind.
  • Non-asbestos inorganic fibers were more abundant than asbestos fibers and were found in almost all samples.
  • Under the microscope, a positive-control lung showed a low degree of interstitial fibrosis and asbestos bodies. Casale Monferrato rat lungs showed no similar lesions, only inflammatory lesions.
  • None of the wild rats showed signs of the infections leptospirosis or tularemia at necropsy, and PCR tests were negative.
• The authors' conclusion: The authors concluded that measuring lung fiber burden in wild rats was feasible, allowing asbestos fibers to be detected and characterized, and that this provides a rationale for using wild rats as sentinels of soil asbestos contamination in Casale Monferrato. They also stated that the crocidolite indicates a likely dispersion source in the town.
• Limitations the authors state:
  • A few fibers may have been lost during sample preparation. Samples with no fibers detected were recorded as 0.
  • Asbestos was not detected in every rat from each area, so more than one rat per area is needed. Finding out how many rats are needed was one aim of the pilot.
  • No official methods exist for counting fibers in biological samples.
  • The technique could not firmly tell tremolite from actinolite. Some fibers also could not be classed as chrysotile or as non-asbestos antigorite and were grouped as fibrous serpentine.
  • The Asti lung samples showed severe decomposition (autolysis), which affected their microscopic examination.

Topics

Medical terms in this study, explained in our Lexicon: Environmental Exposure, Casale Monferrato, Fiber Burden, Scanning Electron Microscopy (SEM), Chrysotile, Crocidolite, Grunerite.

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