VANCOUVER—Researchers have discovered that sediment off the B.C. coast — Canada’s top oyster growing region — is widely polluted with microplastics, and are now calling for further study to examine how this contamination is affecting shellfish sold in restaurants and grocery stores across the country.

The study, conducted by Leah Bendell, a professor of marine ecology and ecotoxicology at Simon Fraser University, and two colleagues, was published by the scientific journal PLOS ONE on Tuesday. It outlines the results of sampling at 16 sites off the coasts of Vancouver and Denman islands in B.C.’s Baynes Sound and Lambert Channel.

The research findings suggest the microplastics, plastic particles that are less than 5mm in diameter, in the study area stems from two sources: the shellfish industry itself and urban pollution.

While microplastics were found at all sites, “extremely high concentrations” of microbeads were found at three of them, Bendell said in an interview, calling the discovery “very alarming.”

Microbeads have been found to accumulate trace metals, she said, so the high quantity found in sediments on the B.C. coast raises serious questions about whether microbead pollution will also increase the concentration of metals. And if it does, how those toxic metals will cycle through food webs.

“The ultimate question is — is it going to have an impact on human health for us that ingest them,” she said.

There are two bodies of thought, Bendell said, one that says microbeads don’t absorb metals and one that says they do.

Previous research has found oysters and other shellfish do ingest microplastics and the pollutants have a negative effect on shellfish health and reproduction, Bendell’s study notes.

“It would just be really prudent to find out are they taking up the microbeads and if so, are they carrying contaminants, and if so is the organism itself affected and are there implications for human health?” she said.

Chris Pearce, a research scientist with Fisheries and Oceans Canada, said the federal department is also concerned about the impact of microplastics on shellfish. They’ve been studying the issue for the past two years with government and industry funding, he said.

That research has revealed microplastics in the water, sediments and in shellfish. Unlike Bendell’s study, Pearce said Fisheries and Oceans researcher have found mostly microfibres, which they believe stem from municipal sewage and textiles, not the aquaculture industry.

Overall, they’re finding relatively low numbers of plastic particles in the shellfish themselves, though it’s still unknown exactly how that affects their health. In lab tests, shellfish do show some stress when they’re fed microplastics, he said.

“We really have no idea the health implications of microplastic particles for humans,” he added.

More research is needed on the health impacts of microplastics on shellfish and the people and animals that eat them, he said.

While Pearce noted that the risks from microplastics in shellfish have to be considered within the context that there are microplastics in everything we eat and even in the air we breathe.

“It’s not an aquaculture problem, it’s a worldwide problem and it impacts every food industry,” he said.

But Bendell said the results of further research investigating the environmental health impacts of microplastics could be particularly important for the shellfish industry. It’s the “canary in the mine” because it depends on the natural processes that could be negatively affected by microplastic pollution, she said.

Shellfish farmers are “very hardworking people and they just get nailed from all directions. They’re dealing with issues like ocean acidification, increased incidences of shell born disease, different types of viruses coming through and now we’re dealing with plastics,” Bendell said.

“They’re the first casualty of what we’ve done to our oceans, they are the ones that are experiencing absolutely full-force the consequences of our activities over the past 50 to 70 years,” she said.

There are broader environmental consequences too.

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“If this is happening to the farmed shellfish you can bet it’s happening to all the wild shellfish, so it’s not just an industry issue,” she said.

According to the United Nations Environment Program, at least eight million tonnes of plastics wind up in the ocean every year. Microplastics make their way into the environment through different means. They can be found in things such as toothpaste or skincare products and may flake off synthetic clothing during machine washing.

Typically, sewage treatment doesn’t filter out these microplastics, which are then released into the ocean, lakes or rivers. Microplastics can also be found in industrial products or can be created as larger plastic debris disintegrates.

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