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Professors Chelsea Rochman (left, Ecology and Evolutionary Biology) and Bob Andrews (right, CivMin) have joined forces to develop new techniques for analyzing microplastics and nanoplastics in drinking water. (Photo: Tyler Irving)

Is there plastic in your drinking water? Professors Bob Andrews (CivMin) and Chelsea Rochman (Ecology and Evolutionary Biology) say there is — but right now, researchers don’t know much more than that.

“If someone asks me how microplastics in drinking water influence human health, I have to say that we have no idea,” says Rochman. “But we should be concerned that the mismanagement of our waste has come back to haunt us.”

Plastic never really goes away. While some waste plastic is recycled or incinerated, most ends up in landfills or worse. A world-leading expert on the fate of plastic waste, Rochman has documented how it ends up in oceans, lakes, rivers, as well as along their shores and even in the bodies of aquatic animals.

“All of the big stuff that you see eventually gets broken down by sunlight into smaller and smaller pieces,” she says. When they become small enough a microscope is required to see them — anywhere from a few millimetres down to a few micrometres — they are referred to as microplastics.

As with larger plastic pieces, microplastics are found widely in the environment. Rochman and her team have even extracted them from the bodies of fish for sale in a commercial market.

Concern over microplastics has been floating just below the surface for some time, but it wasn’t until the fall of 2017 that the issue of microplastics in drinking water hit headlines in a big way.

A non-profit group called Orb Media took samples of tap water from around the world, found microplastics in most of their samples, and released their results to the media. As a member of both the Drinking Water Research Group and the Institute for Water Innovation, Andrews knew that his collaborators would be curious about the story.

“Within hours, I got calls from a couple of the major water providers in southern Ontario that I work with, asking me what we were doing on this topic,” he says.

Despite his long experience collaborating with drinking water providers on treatment and technology, Andrews had not researched the issue of microplastics before. So he sought out advice from Rochman, who at first was similarly skeptical.

“I said, ‘I don’t think they’re going to be there, but sure, let’s filter some water and have a look,’” says Rochman. “We did, and they were there.”

Rochman and Andrews examine tiny plastic particles extracted from Toronto’s harbour. Even smaller particles — micrometres in size — have been found in drinking water from around the world. (Photo: Tyler Irving)
Rochman and Andrews examine tiny plastic particles extracted from Toronto’s harbour. Even smaller particles — micrometres in size — have been found in drinking water from around the world. (Photo: Tyler Irving)

The traditional approach to dealing with drinking water contaminants, such as heavy metals or organic compounds, is for scientists to determine a target threshold below which the risk to human health is considered minimal. Drinking water authorities then invest in treatment technologies designed to keep the levels of these contaminants below the threshold.

But there is no existing threshold for microplastics, and developing one will be complex for several reasons.

First, plastic interacts differently with the body depending on how big the pieces are. “What we’ve seen in animals is that larger pieces usually just get excreted,” says Rochman. “But the smaller particles can actually leave the gut and go into tissues, which is when you can get inflammation and other problems.”

Another challenge is that there are no standardized methods for testing levels of microplastics in drinking water. Different teams employing different techniques could obtain different results, making it hard to compare scientific studies with one another.

Contamination is also an issue — tiny plastic particles shed from clothes, carpets and upholstery can get into the samples and skew the results.

These challenges are further compounded by the fact that microplastics can break down into even smaller particles, known as nanoplastics. Nanoplastics may behave differently from microplastics, but information is scarce because methods for detecting them are not merely non-standardized — they haven’t even been invented.

“Right now, we don’t have good techniques for handling nanoplastic particles,” says Andrews. “One strategy we’re considering is to concentrate them, burn them, and analyze the gas to determine what types of plastic are there. We’d then have to back-calculate to determine their initial concentrations.”

Andrews and his team also have experience testing the toxicity of various compounds on cells grown in the lab. While they may one day go down this route for nanoplastics, for now Andrews and Rochman emphasize the importance of improved analysis as a key step toward developing policies to address the challenge of microplastics.

“California has already passed laws mandating the monitoring of microplastics in drinking water and in the ambient environment,” she says. “I think it’s good that those bills happened, because they are now forcing this global methods development program, which we’re helping lead. We don’t want to throw out numbers until we feel that we have a sound method.”

The collaboration between Rochman and Andrews is funded in part by XSeed, an interdivisional research funding program designed to promote multidisciplinary research. XSeed projects include one principal investigator from U of T Engineering and one from another University of Toronto division, in this case, the Faculty of Arts & Science.

Learn more about the latest cohort of projects funded through XSeed

“Dealing with microplastics is the kind of challenge that truly does require people from different disciplines to work together,” says Andrews. “Neither of us could do this alone.”

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Marit Mitchell
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