DAVIS, Calif. — Disease-causing parasites could be pouring into the ocean after hitching a ride on microplastics, warns a new study. The tiny pieces of plastic could spread dangerous diseases to humans — some of which can prove fatal for kids, say scientists.
Plastic particles, no bigger than a grain of rice, known as microplastics, have contaminated the four corners of the ocean, even the most remote waters in Antarctica. The amount of plastic trash that flows into the oceans every year is expected to nearly triple by 2040.
Now scientists at the University of California, Davis are showing plastic pollution could be harmful in more ways than one.
“It’s easy for people to dismiss plastic problems as something that doesn’t matter for them, like, ‘I’m not a turtle in the ocean; I won’t choke on this thing,” says study corresponding author Karen Shapiro, an infectious disease expert and associate professor in the UC Davis School of Veterinary Medicine, in a statement. “But once you start talking about disease and health, there’s more power to implement change. Microplastics can actually move germs around, and these germs end up in our water and our food.”
Three disease-causing pathogens were included in the study which can infect both humans and animals. Toxoplasma gondii, a parasite found in cat feces, which infects many sea creatures and causes a disease called toxoplasmosis. The illness has been linked with deaths among sea otters and critically endangered wildlife like Hector’s dolphins and Hawaiian monk seals. In humans, the condition can cause life-long illnesses, as well as developmental and reproductive disorders.
Cryptosporidium (Crypto) and Giardia, two pathogens which can be deadly in young children and people with underlying health conditions, were also examined by the researchers.
“This is very much a problem that affects both humans and animals,” says first author Emma Zhang, a fourth-year veterinary student at the school. “It highlights the importance of a One Health approach that requires collaboration across human, wildlife and environmental disciplines. “We all depend on the ocean environment.”
Experiments were carried out to see whether these harmful parasites could piggyback off of microplastics in seawater. Two different types of plastic were tested, including polyethylene microbeads, which are found in many cosmetics, including exfoliants and cleansers.
They also looked at polyester microfibers, commonly used to make clothing and fishing nets. More parasites stuck to the fibers than the breads, although both were suitable, the researchers say.
“Plastic makes it easier for pathogens to reach sea life in several ways, depending on whether the plastic particles sink or float,” says Shapiro.
Pieces of plastic on the surface can travel long distances and spread diseases far from their original source on land. But those which sink could concentrate pathogens near the ocean floor, known as the benthos environment. This is where filter-feeding animals like plankton, clams, mussels, oysters and other shellfish live.
“When plastics are thrown in, it fools invertebrates,” adds Shapiro. “We’re altering natural food webs by introducing this human-made material that can also introduce deadly parasites.”
A single load of laundry in the wash can shed up to 700,000 microplastic fibers which reach waterways through waste systems. But there are several ways that people can reduce their microplastic footprint, the researchers say. Choosing clothes made from natural fibers and avoiding cosmetic products made with plastic beads is one example.
“This work demonstrates the importance of preventing sources of microplastics to our oceans,” says co-author Chelsea Rochman a plastic-pollution expert and assistant professor of ecology at the University of Toronto. “Mitigation strategies include filters on washing machines, filters on dryers, bioretention cells or other technologies to treat stormwater, and best management practices to prevent microplastic release from plastic industries and construction sites.”
The findings are published in the journal Scientific Reports.
Report by South West News Service writer Tom Campbell.