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Viruses survive in fresh water by clinging to microplastics, study finds

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The impacts of marine plastics on wildlife are already well known and studied, even revealing unique ecosystems. But little research has been done to understand the human health risks posed by surface-bound pathogens. Microplastics are perfect islands for harboring viruses and bacteria in wastewater. Currently, no degradation method is used to counter this contaminant during wastewater treatment. Moreover, the potential for human viral pathogens to associate with this “plastisphere” has never been quantified. Recently, and for the first time, scientists have proven that viruses can survive and remain infectious for up to 3 days by attaching to plastics in fresh water, raising concerns about the potential health impact human.

Microplastic pollution (i.e. plastic particles < 5 mm) has received particular attention, due to their high concentration and potential for large-scale dissemination in environments. terrestrial, freshwater, marine and atmospheric. Once in the environment, plastics can be quickly colonized by microorganisms. Moreover, studies have been conducted to describe and identify the microbial communities that develop within this “plastisphere”.

Places where high concentrations of microplastics are exposed to high loads of human pathogens (e.g., tributaries and settling ponds of sewage treatment plants) provide an ideal environment for the formation of biofilms on the surface microplastics. The presence of a biofilm on microplastics is also probably the most important factor for viruses to bind to their surface.

The concentration of human pathogenic bacteria colonizing microplastics is reduced in treated effluent, compared to incoming wastewater. However, unlike bacteria, some viruses, especially non-enveloped enteric viruses, are less sensitive to inactivation processes such as UV irradiation, chlorine or ozone, used in wastewater treatment. Their increased persistence in wastewater treatment plants could facilitate their interaction with biofilm components on microplastics and promote the dissemination of dangerous viruses in fresh water, such as those in lakes.

Recently, the team of researchers, led by Dr. Richard Quilliam from Starling University, conducted the world’s first study on the evaluation of the interactions between viruses and microplastics, as well as the stability potential of these viruses. and their dissemination on a larger scale in fresh water. Their surprising and disturbing results are published in the journal Environmental Pollution.

“Hitchhiking” of viruses on plastic, a large study

This study is therefore the first to explore the problem of microplastics in water and its link with pathogens, using water taken from the natural environment. Indeed, previous research has focused only on the spread of these viruses in sterile hospital environments.

Not to mention that this research is part of a larger £1.85m project started in 2018. Working with the universities of Bangor and Warwick, it aims to understand how plastics act as vehicles, with the potential to spread pathogens in coastal areas, even from country to country, and how this affects health. Moreover, this is already the case for certain living beings, other than bacteria and viruses. If these species are transported on plastic debris, they not only survive, they colonize the high seas. GarbagePatch).

Although most WWTPs are very effective at removing microplastics from wastewater influent (e.g. up to 99%) and concentrating them in the sludge, treated effluent continues to be one of the main sources of microplastics entering the environment. The interaction of human viruses with this floating and persistent substrate could be beneficial for their survival and infectivity in the environment.

This recent area of ​​research will likely lead to new environmental guidelines, strategies and management plans designed to reduce the possibility of viruses binding to microplastics and ending up in fresh, treated water. Not to mention that the specific characteristics of each virus can influence their interaction with the biofilm and therefore their persistence.

Dr Quilliam explains in a press release: “ Even if a treatment plant does everything it can to clean the wastewater, the discharged water still contains microplastics, which are then transported along the river, in the estuary, and end up on the beach. We didn’t know how well viruses could survive hitchhiking on plastic in the environment, but they survive and stay infectious ».

Viruses protected by plastic

In this context, the researchers tested two types of viruses, those with a “lipid envelope” around them, like the influenza virus, and those without an envelope, like enteric viruses (rotavirus and norovirus). Rotavirus, which causes diarrhea and upset stomach, survived up to three days in the lake water tested, attaching itself to the surface of microplastics.

Sure enough, they found that in viruses with an envelope, the latter quickly dissolved and the virus was deactivated, while those without an envelope successfully bound to microplastics and survived. Virus particles would be protected against inactivation factors when associated with biofilm on microplastics and when there is a high concentration of particulate matter in the water.

Dr. Quilliam points out: “ Microplastics are so small they could potentially be ingested by someone swimming, and sometimes they wash up on the beach as brightly colored lentil-sized pellets called ‘nurdles’, which children could pick up and put in their mouths. It doesn’t take a lot of virus particles to make you sick. And if the viruses then release themselves from the plastic into the water or sand, their persistence in the environment is increased ».

Although the results suggest that the presence of an envelope can limit the interaction of the virus with the plastisphere, the ability of viruses to remain infectious, via the colonized “nurdles”, highlights a risk of contamination and becomes an issue of public health. Human exposure to microplastics in the environment is a new consequence of disregard for nature. Recently, plastic particles have been found in the blood of living people and even the brain. We pollute ourselves and make ourselves sick by the simple fact of our activities.

Source : Environmental Pollution

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