Wild rats as urban detectives for latent sources of asbestos contamination

Our plain-English summary of Wild rats as urban detectives for latent sources of asbestos contamination, by F. Ingravalle, L.A. Ceballos, V. D'Errico, et al (The Science of the Total Environment, 2020).

The study

• Authors: F. Ingravalle, L.A. Ceballos, V. D'Errico, D. Mirabelli, S. Capella, E. Belluso, M. Pezzolato, E. Bozzetta, A. Dondo, A. Di Blasio, S. Meistro, C. Vizio, E. Fraccaro, M. Ardizzone, A. Seghesio, G. Ru
• Journal: The Science of the Total Environment
• Published: 2020;729:138925
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Based on a large body of evidence asbestos minerals have been classified as carcinogens. Despite the Italian ban on asbestos in 1992 and the subsequent remediation activities, latent sources of contamination may still represent a hazard where asbestos were particularly used. Using wild rats as sentinel animals, this study aimed at uncovering sites with the greatest potential for non-occupational exposure to asbestos in the city of Casale Monferrato (Piedmont Region, Italy), where the largest Italian manufacturing plant of asbestos-cement had been active. During the study period (2013-2015) a total of 40 wild rats were captured from 16 sampling capture points. The lungs of wild rats have been investigated by using scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). The SEM-EDS detected the presence of asbestos fibers (tremolite/actinolite, amosite, and chrysotile) in rats' lungs from 11 sampling points. The hypothetical rats' home-range and the observed site-specific concentration of asbestos fibers per gram of dry lung tissue were used to identify areas to be targeted by additional search of latent sources of asbestos. In conclusion, our results showed that the use of wild rats as sentinel animals may effectively integrate the strategies currently in use to reduce the exposure to asbestos.

Copyright © 2020 Elsevier B.V. All rights reserved.

In plain English

This study used wild rats as 'sentinel animals' to look for hidden sources of asbestos in Casale Monferrato, Italy, where the country's largest asbestos-cement plant had operated. From April 2013 to June 2015, 40 rats (37 Rattus norvegicus and 3 Rattus rattus) were obtained from 15 sampling points in the city and one control location outside it. Of these, 38 were caught in traps and 2 were caught by a cat near a trap. Lung tissue from 36 rats, grouped into 19 pools, was examined by scanning electron microscopy. Eleven pools contained asbestos fibers. Tremolite/actinolite was the most common, followed by amosite and by chrysotile, which included fibers that could not be told apart from antigorite. No crocidolite was found. In the 11 positive pools, the mean concentration was 0.301 × 10^5 fibers per gram of dry lung tissue. Two nearby sampling points, F2_3 and F2_1, had unusually high levels, and the authors suggested the area around them as a possible hot-spot. Asbestosis was diagnosed in 2 rats and suspected in 9 others. The authors concluded that the approach could help public health campaigns target asbestos removal. They reported catching fewer rats than expected.

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 biomonitoring study using captured wild rats as sentinel animals, with lung fiber analysis by scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and histopathology
• Who was studied: 40 wild rats (37 R. norvegicus, 3 R. rattus) obtained from 15 sampling points in the city of Casale Monferrato (old town and the 1960s–70s area) plus one suburban control location 2.5 km away, mid-April 2013 to end-June 2015. Thirty were caught in multiple-capture traps, 8 in snap traps and 2 by a cat. Of these, 38 were available for histopathology and 36 for SEM-EDS, analyzed in 19 pools.
• Exposure: Non-occupational environmental exposure to asbestos in an urban area with a history of asbestos-cement manufacturing. Lung fibers were classified as chrysotile, actinolite, amosite, anthophyllite, crocidolite or tremolite.
• Main results:
  • Of 19 lung pools, 11 contained asbestos fibers. Eight of these were pools from heavier rats weighing 100 g or more.
  • Across the 11 asbestos-positive pools, the mean asbestos fiber concentration was 0.301 × 10^5 fibers per gram of dry lung tissue (sd 0.271 × 10^5).
  • Tremolite/actinolite was the most common asbestos type (43 fibers in 9 pools, 16 rats; mean 0.244 × 10^5 per gram of dry tissue). It was followed by amosite (9 fibers in 2 pools, 7 rats; 0.230 × 10^5) and by chrysotile/asbestiform antigorite (9 fibers in 6 pools, 12 rats; 0.111 × 10^5).
  • No crocidolite fibers were detected.
  • Outlier (unusually high) concentrations were found at sampling point F2_3 (MAD-score 4.38; 0.816 × 10^5 per gram of dry tissue) and at F2_1 (pool of heavier rats, MAD-score 3.71). Their 100 m buffer areas overlapped, which the authors described as consistent with a hypothesized asbestos hot-spot.
  • A histopathological diagnosis of asbestosis was made in 2 rats from one sampling point (F1_1), where both corpuscles and severe and moderate fibrosis were found.
  • In 9 further rats from 7 sampling points, asbestosis was hypothesized because Perls staining was positive together with fibrosis, but no ferruginous bodies were seen.
• The authors' conclusion: The authors concluded that wild rats are a helpful sentinel of latent asbestos sources and that at least one location in Casale Monferrato could be a hot-spot. They also concluded that the approach can be used in public health campaigns to address asbestos removal.
• Limitations the authors state:
  • Fewer rats were captured than expected, despite large bait consumption.
  • SEM-EDS could not always distinguish chrysotile from asbestiform antigorite. Such fibers were conservatively counted as chrysotile.
  • Tremolite and actinolite cannot be distinguished by SEM-EDS, so they were grouped together.
  • The authors stated that the method needs confirmation by comparing fibers in rat lungs with fibers found in air and soil in the same area.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos, Non-Occupational Exposure, Casale Monferrato, Asbestos-Cement, Scanning Electron Microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Tremolite, Actinolite.

Related studies

• The wild rat as sentinel animal in the environmental risk assessment of asbestos pollution: a pilot study — M. Ardizzone, C. Vizio, et al. (2014)
• The use of wild animal models to detect evidence of environmental contamination by asbestos-like substance — R. Puleio, M.R. Schiavo, et al. (2013)
• Fenton reaction induced cancer in wild type rats recapitulates genomic alterations observed in human cancer — S. Akatsuka, Y. Yamashita, et al. (2012)
• Respirable inorganic fibers dispersed in air and settled in human lung samples: Assessment of their nature, source, and concentration in a NW Italy large city — S. Capella, D. Bellis, et al. (2020)
• Malignant peritoneal mesothelioma in a boar who lived in Calabria (Italy): Wild animal as sentinel system of human health — E. Colombino, S. Capella, et al. (2019)
• The latent form of TGFbeta(1) is induced by TNFalpha through an ERK specific pathway and is activated by asbestos-derived reactive oxygen species in vitro and in vivo — D.E. Sullivan, M. Ferris, et al. (2008)

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