Study sheds light on human consumption of microplastics

A study from the University of Victoria has for the first time compiled research on microplastics to try to estimate just how much people are consuming.

Microplastics are pieces of plastic that are just under five millimetres in diameter — or smaller than the size of a sesame seed — that come from the degradation of larger plastic products or the shedding of particles from water bottles, plastic packaging and synthetic clothes. 

Garth Covernton, a PhD candidate at University of Victoria's department of biology, said his team looked at 26 papers assessing the amount of microplastics found in individual food items.

The study found that a person's average microplastic consumption — based on those food items previously analyzed — would likely be somewhere between 70,000 and 121,000 particles per year. While younger girls were at the lower end of the spectrum, adult men were at the high end.

People who consume a lot of bottled water could see that number jump by up to 100,000 particles per year. 

The study analyzed the amount of microplastics found in fish, shellfish, sugars, salts, alcohol, water and air, which account for 15 per cent of Americans' caloric intake.

But the other 85 per cent of what people consume, like beef, poultry, dairy and grains, has still not been examined.

Covernton compared the study to early understandings of cigarettes and tobacco: While the numbers they came up with did seem large, they don't yet know exactly what level of consumption is dangerous.

"We're at the point where we know microplastics at some dose could be harmful, but we're not at the point where we can say whether what the average person is encountering is the equivalent of one cigarette in a lifetime, or that chronic exposure, like a pack a day."

Covernton said the findings demonstrate more work needs to be done to understand how the tiny particles might affect human health.

'An early warning'

The health consequences of microplastics entering the human body are still largely unknown, but Rolf Halden, a professor at Arizona State University who has studied the effects of toxic chemicals on the human body, said the study should serve as an "early warning."

Halden said research shows that human-made objects that end up in the body can trigger inflammation, "and inflammation is a precursor of cancer. This doesn't necessarily mean that we get cancer from these particles, but there is a potential and we don't know enough about this today." 

Microplastics can range from small pieces of plastic visible to the human eye, to tiny particles the size of cells. Past research has suggested that smaller particles may be far more dangerous, as they can be absorbed into the body's tissue, where they'll remain forever.

"We know that some particles can make it through the gut into the bloodstream. We've made observations that some of the microplastics are in tissues that are diseased, but we don't know how much it takes, and what fraction of the population will get sick from exposure to microplastic," said Halden.

Even clothing made out of synthetic fabrics, like nylon, polyester, and acrylic spandex, can shed synthetic fibres that end up in our bodies.

"Just the fact that we put these numbers together and you get such a high estimate of particular exposure — what would that look like if we were to fill in those gaps and get the whole story?" said Covernton.

Long-lasting plastics

Most studies of plastics have focused on the oceans.

Peter Ross, president of Research Ocean Wise, said there are two main effects that have been observed in sea life: structural toxicity, when plastic literally blocks the gills or the stomach of a fish, convincing the animal that it's full and causing it to starve to death; and exposure to endocrine-disrupting chemicals that can have other effects on the body.

"A lot of plastics have hardening agents like BPA or they have phthalates, or they have flame retardants in them," he said.

"So if humans or other species are exposed to these, that's cause for concern, from a toxicological standpoint."

Covernton said his team is now calling for more research to understand just how much a lifetime of exposure to microplastics will affect human health.

"The biggest issue with these particles is they don't seem to really go away. If anything, they'll probably just increase in concentration over time, because plastic unfortunately doesn't break down in the environment over a human lifetime," he said.

"It may seem overwhelming, but I think there are solutions if we deem it to be a problem. We just need to come together to get there," said Covernton.