Science and Technology Daily, Beijing, April 27 (Intern reporter Zhang Jiaxin) Microplastics can bring pathogens from land into the ocean, potentially affecting the health of humans and wildlife, according to a study by the University of California, Davis. The study, published on the 26th in the journal Scientific Reports, is the first to link microplastics in the ocean to pathogens on land. The study found that microplastics can make it easier for disease-causing pathogens to concentrate in plastic-contaminated areas of the ocean.

The pathogens studied this time included Toxoplasma gondii, cryptosporidium and Giardia, which can infect both humans and animals.

"It's easy for people to dismiss plastic as something that doesn't matter to them, like 'I'm not a turtle in the ocean, I'm not going to choke on this stuff.'" "But microplastics can actually spread bacteria around, and those bacteria end up in our water and food," said corresponding author Karen Shapiro, an infectious disease specialist and associate professor at the University of California, Davis, School of Veterinary Medicine.

Microplastics are tiny plastic particles smaller than 5 millimeters. Smaller than a grain of rice, they pollute waters as far away as Antarctica. The study shows that by hitching a "free ride" on microplastics, pathogens can spread throughout the ocean, reaching places where terrestrial parasites would normally never be found.

Toxoplasma, a parasite found only in cat feces, has infected many Marine species and even killed critically endangered wildlife, including humpback dolphins and Hawaiian monk seals. In humans, toxoplasmosis can cause lifelong illness, as well as developmental and reproductive disorders.

Cryptosporidium and Giardia cause gastrointestinal disorders that can be fatal in young children and immunocompromised people.

In this study, the authors conducted laboratory experiments to test whether the selected pathogens were associated with plastics in seawater. They used two different types of microplastics: polyethylene microbeads and polyester microfibers. Microbeads are often found in cosmetics, such as exfoliating oils and cleaners, while microfibers are found in clothing and fishing nets.

Scientists have found that both types of plastic can carry terrestrial pathogens, and that more parasites cling to the microfibers than to the microbeads. The tiny microfiber particles, which are common in California waters, have also been found in shellfish.

Plastic makes it easier for pathogens to enter Marine life in a number of ways, depending on whether the plastic particles sink or float, the authors say. Floating on water, microplastics can travel long distances, spreading pathogens far from their terrestrial sources. Plastics that sink to the ocean floor may accumulate pathogens in benthic environments near the ocean floor. That's where filter-feeders like zooplankton, clams, mussels, oysters, abalone, and other shellfish live, increasing their likelihood of ingesting plastic and pathogens.

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