Microplastics Heath Risk Discovered in Hitchhiking Vomiting Viruses

Viruses that cause vomiting and diarrhea can remain infectious in water by attaching to microplastics, according to research published in the journal Environmental Pollution.

Microplastics, which are defined as being less than 5mm long, are commonly found in both freshwater and seawater thanks to the widespread occurrence of plastic pollution. Eleven million metric tons of plastic waste are estimated to enter the ocean every year. Larger chunks of plastic are mechanically broken down into microplastic particles.

These microplastics then make their way into our food, tap water, bottled water, beer, and even the air we breathe. One German study even found that between 2014 and 2017, plastic byproducts were found in the blood and urine of 97 percent of children tested, Deutsche Welle reported.

Microplastics are swiftly occupied by bacteria and viruses, which have long been hypothesized to last longer and travel further than free-floating microorganisms. The latest paper is the first formal quantification of human pathogens residing on microplastics.

"We found that viruses can attach to microplastics and that allows them to survive in the water for three days, possibly longer," Richard Quilliam, lead researcher on the project at the U.K.'s Stirling University, told The Guardian.

"We weren't sure how well viruses could survive by 'hitchhiking' on plastic in the environment, but they do survive and they do remain infectious," he said.

In the latest study, researchers used two species of model viruses and measured how they bound to microplastic pellets in three different types of water: filtered and unfiltered surface water, and surface water with added nutrients. The two model species were rotavirus (RV) SA11—a human gastrointestinal virus—and the bacteriophage virus Phi6.

Rotavirus does not have a protein and lipid casing called an envelope, while the bacteriophage does. These envelopes allow a virus to multiply within a cell without destroying it.

Researchers found viruses hitchhiking on the microplastic pellets were more stable compared to those residing in the water, being able to survive up to three days. By binding to the microplastic surface, virus particles were protected against factors like ultraviolet light that would normally kill them, especially if there was a high concentration of microplastics present.

"The ability to recover both enveloped and non-enveloped infectious viruses from colonized microplastic pellets highlights an additional potential public health risk of surface waters becoming contaminated with microplastics, and subsequent human exposure to microplastics in the environment," the researchers wrote.

The rotavirus, which is a human pathogen, fared better than the bacteriophage virus, with more retrovirus particles being present on the microplastics at the end of the testing period. This indicates that having a protein and lipid envelope may limit the virus' ability to interact with the microplastics.

Non-enveloped viruses, including norovirus, enterovirus, adenovirus, and rhinovirus, are typically more virulent, as to leave the cell they must destroy it. Pathogens found in sewage, including E. coli bacteria, have previously been found by the same research group on small pieces of plastic litter washed up on Scottish beaches.

These two discoveries could have far-reaching implications for human health worldwide, with harmful viruses and bacteria being able to travel across oceans without human carriers.

"The recovery of both virus models used in this study emphasizes the potential for plastic pollution to act as a novel pathway for viral dissemination and persistence in the environment," the study said.