Environmental contamination of chrysotile asbestos and its toxic effects on antioxidative system of Lemna gibba

Our plain-English summary of Environmental contamination of chrysotile asbestos and its toxic effects on antioxidative system of Lemna gibba, by A.K. Trivedi, I. Ahmad, M.S. Musthapa, et al (Archives of Environmental Contamination and Toxicology, 2007).

The study

• Authors: A.K. Trivedi, I. Ahmad, M.S. Musthapa, F.A. Ansari
• Journal: Archives of Environmental Contamination and Toxicology
• Published: 2007;52(3):355-62
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Asbestos was monitored in various plant samples around an asbestos cement factory. Asbestos residue was found on the surface of all plant samples monitored. Based on asbestos concentration found in different plant samples during monitoring and on the property of asbestos to cause reactive oxygen species-mediated oxidative stress in animal models, laboratory experiments were conducted to assess the toxicity of chrysotile asbestos on an aquatic macrophyte, duckweed (Lemna gibba.). L. gibba plants were exposed to four concentrations (0.5, 1.0, 2.0, and 5.0 microg/mL) of chrysotile asbestos under laboratory conditions, and alterations in the glutathione and ascorbate antioxidative system were estimated at postexposure days 7, 14, 21, and 28 in order to assess changes in their level as suitable biomarkers of chrysotile contamination. Chrysotile exposure caused a decrease in total and reduced glutathione and an enhancement in the oxidized glutathione as well as the reduced/oxidized glutathione ratio. An increase in ascorbate pool size, and reduced as well as oxidized ascorbate was found to be accompanied by a decrease in the ratio of reduced/oxidized ascorbate. Alteration in the glutathione and ascorbate level might be considered as a biomarker of exposure to an unsafe environment because these are essential compounds of the general antioxidative strategy to overcome oxidative stress due to environmental constraints. Because an increase in the oxidation rate of antioxidants weakens cellular defenses and indicates a precarious state, they could constitute indicators of toxicity.

In plain English

This study from India had two parts, and both dealt with plants, not people. First, the authors collected leaves from 21 kinds of land plants around an asbestos cement factory about 25 km from Lucknow. They counted the asbestos fibers washed off the leaves, averaging three years of sampling. Asbestos fibers were found on all plant samples, and most were longer than 20 micrometres. Second, in the laboratory, the authors exposed duckweed (Lemna gibba), a small water plant, to chrysotile asbestos for 28 days. The results describe four doses, 0.5, 1.0, 2.0 and 5.0 micrograms per frond. The authors measured two protective chemicals in the plant, glutathione and ascorbate. At day 28, compared with untreated plants, total glutathione fell by 46.49% to 69.87% and its oxidized form rose by 85.10% to 117.35%. Total ascorbate rose by 29.18% to 79.41%. The ratio of reduced to oxidized ascorbate fell from 3.38 in untreated plants to 2.03 at the highest dose. The authors concluded that these chemicals might serve as markers of asbestos contamination and as an early sign of toxicity, but that field testing is still 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: Field monitoring of asbestos fibers on plant leaves near a factory, plus a laboratory exposure experiment on a plant (duckweed)
• Who was studied: Field part: 21 species of terrestrial plants around an asbestos cement factory at Mohanlalganj, about 25 km from Lucknow, Uttar Pradesh, India. Ten samples of each plant were collected quarterly, and the data are an average of three successive years. Laboratory part: duckweed (Lemna gibba) collected from a natural water body, grown in five replications of five Petri dishes with 20 plants each. Reported data are the mean of three independent experiments.
• Exposure: Field part: asbestos fibers deposited on leaf surfaces near the factory. Laboratory part: chrysotile fibers smaller than 30 micrometres. Suspensions of 0.5, 1.0, 2.0 and 5.0 g of chrysotile per litre of water were applied to the fronds (5 microlitres per frond, twice a week). The growth medium also contained 0.1 g per litre of chrysotile. Control plants were grown without chrysotile, and exposure lasted 28 days. The results report the doses as 0.5, 1.0, 2.0 and 5.0 micrograms per frond.
• Main results:
  • Asbestos fibers were found on the surface of all plant samples monitored around the factory.
  • In Table 1, total fibers per gram dry weight ranged from 57 (Lagenaria siceraria, lauki) to 174 (Cyanodon dactylon, doob grass). Fibers longer than 20 micrometres made up 59.09% to 80.0% of fibers, depending on the plant.
  • In exposed duckweed, total glutathione was 46.49%, 55.63%, 59.30% and 69.87% lower than in controls at day 28, for the 0.5, 1.0, 2.0 and 5.0 microgram-per-frond doses respectively. At day 7, the decreases were 9.92% to 21.31%.
  • Reduced glutathione (GSH) in exposed duckweed decreased by 5.14% to 14.40% at day 7 and by 38.67% to 70.67% at day 28, across the four doses.
  • Oxidized glutathione (GSSG) in exposed duckweed increased by 14.10% to 43.85% at day 7 and by 85.10% to 117.35% at day 28, across the four doses.
  • The ratio of reduced to oxidized glutathione was 19.37 in control plants. In exposed plants it fell to 18.51 to 16.25 at day 7 and to 8.85 to 8.52 at day 28.
  • Total ascorbate in exposed duckweed increased by 8.71% to 21.57% at day 7 and by 29.18% to 79.41% at day 28, across the four doses.
  • Reduced ascorbate (AsA) in exposed duckweed increased up to day 21, by 18.82% to 56.99% across the four doses, then decreased slightly at day 28.
  • Oxidized ascorbate (DAsA) in exposed duckweed increased by 32.73% to 40.27% at day 21 and by 30.36% to 35.54% at day 28, across the four doses.
  • The ratio of reduced to oxidized ascorbate was 3.38 in control plants. In plants given 5.0 micrograms per frond, it fell to 2.03 at day 28.
• The authors' conclusion: The authors concluded that antioxidant content in Lemna gibba might serve as a suitable biomarker of exposure to environmental asbestos contamination and as an early indicator of toxicity.
• Limitations the authors state:
  • The authors stated that further research is needed to validate the use of these markers under field conditions.

Topics

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

Medical terms in this study, explained in our Lexicon: Chrysotile, Asbestos-Cement, Reactive Oxygen Species (ROS), Oxidative Stress, Glutathione (GSH), Biomarker.

Related studies

• Environmental contamination of chrysotile asbestos and its toxic effects on growth and physiological and biochemical parameters of Lemna gibba — A.K. Trivedi, I. Ahmad, et al. (2004)
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• Different cellular responses evoked by natural and stoichiometric synthetic chrysotile asbestos — E. Gazzano, E. Foresti, et al. (2005)
• An environmental survey in chrysotile asbestos milling processes in India — A.K. Mukherjee, H.R. Rajmohan, et al. (1992)
• The wild rat as sentinel animal in the environmental risk assessment of asbestos pollution: a pilot study — M. Ardizzone, C. Vizio, et al. (2014)

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