Approved Abstracts

DNA damage caused by microplastics in the earthworm



Author(s): Ribeiro O; Gaivão I; Peixoto F; Alves M; Sousa J.R.; Natal-da-Luz T.; Carrola J.S.;
Presenter: João Soares Carrola

Plastics are a versatile, inexpensive and resistant material presenting several advantages to society, however, they cause serious environmental problems. Microplastics (MPs) are fragments with less than 5 mm and currently belong to the group of emerging contaminants. These MPs can be fragmented into very small particles, called nanoplastics. Due to their small size, they can be ingested and accumulate along the food chain. Besides, these particles possess a large surface area, and other pollutants (metals, PCBs, PAHs, etc ) may be adsorbed to their surfaces. Earthworms are important animals in the soil food chain and perform several vital functions in terrestrial systems. Furthermore, earthworms are considered sentinel organisms in soils and since the research on the toxic effects of MPs in terrestrial ecosystems is scarce, it is important to assess the effects of MPs in the terrestrial fauna like the earthworms Eisenia fetida. Thus, this work aimed to evaluate the potential genotoxic effects of MPs in E. fetida. For this purpose, a 28-day sub-lethal ecotoxicological test was carried out under controlled temperature, humidity, and light conditions according to OECD protocol nº 222 (OECD, 2016). An artificial soil composed of 70% quartz sand, 20% kaolin clay and 10% peat, with a pH value adjusted to 6.0 ±0.5, by addition of CaCO3 was used in the laboratory biological assay. Ten earthworms were randomly distributed and exposed to different concentrations of MPs (0, 0.001, 0.01 and 0.2 % of the dry weight of artificial soil), for 28 days. After this period, the comet assay technique was performed to assess DNA damage using fluorescence microscopy, and 100 aleatory comets were classified into five classes: 0 to 4 to assess the genetic damage indicator (GDI) in arbitrary units (AU). The data were analysed through a one-way analysis of variance followed by a Kruskal-Wallis post-hoc test to assess the effect of the concentration of MPs on the DNA damage.
It was observed a dose-response effect, i.e., the increases in MPs concentration led to a rise in DNA damage. This difference was statistically different for the higher concentration 0.2 % dry weight of soil. This increase in DNA damage may be related to oxidative damages since oxidative stress can lead to DNA strands breaks. The DNA damage can affect normal cell replicative function, impact rates of apoptosis, impaired cellular function, cell loss, or the transformation of healthy to cancer cells.
Therefore, the data evidenced that the increase in the concentration of MPs in terrestrial ecosystems can lead to genotoxic problems in earthworms and its population which may be an issue for the food chains. The negative impact can also occur in other soil invertebrates and microfauna. More research is needed to better understand the impacts of microplastics in soil invertebrates and, consequently, on soil services, and food contaminations with potential impact in wildlife (ecotoxicology) and even for humans (when ingesting food produced in agricultural soils polluted with plastics and other pollutants).
Funding: This work was supported by National Funds by FCT - Portuguese Foundation for Science and Technology, under the project UIDB/04033/2020 and UIDB/CVT/00772/2020. Acknowledgments: Centro de Química (UTAD), CITAB, CECAV (UTAD).


Keywords: DNA damage; microplastics; Eisenia fetida

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