It’s estimated that roughly 10,000 tonnes of plastics enter the Great Lakes every year, with higher concentrations in more populated and industrialized areas.

By Dr. Chelsea Rochman

The world saw the first plastic polymer invented in 1869 and its development was hailed as an environmental success. This polymer could replace material such as ivory, commonly used in household items, saving elephants and other animals from poaching. In 1907, the first fully synthetic plastic was developed, marking a new milestone for the environment – a society free from reliance on natural resources such as wood and metal. Since then, plastic production has became cheaper and easier with a variety of applications leading to the ubiquity of plastics, and plastic pollution, that we see today.

Over the past half-century, we have slowly begun to understand that despite the initial optimism, there is increasing environmental contamination across the globe.

One of the key benefits of plastics in commercial use is that the material doesn’t degrade as quickly as paper or wood. Although degradation may be slow, plastic will fragment into smaller and smaller pieces via sunlight or mechanical stress.

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Due to decades of unsustainable materials management practices and recycling programs that fall far short of 100% recovery, plastic has become prevalent in our environment. Due to slow degradation, we find plastic waste products in their original form in the environment, but also in the form of many small pieces of plastic debris – often referred to as microplastics. This is particularly problematic when these plastics enter our water.

Plastic pollution in the Great Lakes

The Great Lakes represent 20% of the world’s freshwater reserves and provides drinking water to more than 30 million people in Canada and the United States. It’s estimated that roughly 10,000 tonnes of plastics enter the Great Lakes every year, with higher concentrations in more populated and industrialized areas. The average concentration of plastic in the Great Lakes ranges from 43,000 particles/km2 to 6.7 million particles/km2, which are concentrations greater than the ocean’s garbage patches.

Microplastics are defined as smaller than 5 mm in size. Photo credit: 5Gyres

These plastics can range from macroplastics (>5mm) to microplastics (<5mm), each of which may start as pellets used in manufacturing, shopping bags or water bottles. Microplastics can also start out very small such as microbeads in beauty products (the manufacture and importation of which was prohibited by the Government of Canada in July 2018).

What risks does this prevalence of plastics in freshwater pose to the health of ecosystems and humans? Some are obvious such as the risk of choking or entanglement of marine animals and fish. Other risks are less visible. Plastics contain many chemical ingredients such as phthalates, which can leach from the plastic over time and have been shown to interfere with normal hormone production in wildlife. At the same time, the composition of plastics allows for persistent organic pollutants, such as DDT pesticides or PBDE (polybrominated diphenyl ethers) flame retardants, to attach themselves to pieces of plastic that are then consumed by wildlife.

Also troubling is that we humans are consuming plastic through the fish and seafood that we eat and even through the tap water we use in our homes every day.

The long-term effects of plastic consumption in wildlife and humans is not yet known. Laboratory experiments indicate that after exposure to microplastics, the common water flea, which is abundant across the Great Lakes and important prey to a variety of species, has hampered growth and reproductive output. Research has also shown that plastic recovered from nature has higher toxicity due to accumulated chemicals versus virgin plastic which has not accumulated these additional persistent organic pollutants.

Identifying the sources of plastic pollution

We know that plastic is prevalent in our ecosystem and there is mounting evidence that it can to some degree effect the growth and reproductive health of some species. As the ones who have created the problem, how do we fix it? To do so, we must understand the source of these plastics.

Categorizing microplastics. Photo credit: Cole Brookson

We think that three main paths exist for plastic to enter the Great Lakes: through wastewater from water treatment facilities, agricultural runoff and urban runoff after rain, or melting events. The highest concentrations of plastics are thought to be within our wastewater and urban runoff. Wastewater contains fibres found in fleece, or other textile products made from plastics. Urban runoff includes foam, films, plastic fragments from litter such as water bottles, food wrappers and cigarette butts, as well as rubber that comes from the wear and tear of vehicle tires on our roads.

As we continue to develop our understanding of where the plastic is coming from, we must also look at how we stem the tide.

Addressing the issue

Plastic pollution in our watersheds is a complex problem and there is no silver bullet to fix it. However, there are many solutions that do exist throughout the life cycle of our plastic goods that can significantly reduce the amount that ends up in our water.

First and foremost, we as individuals and as businesses can reduce the overall use of plastic where appropriate, particularly in single-use products such as shopping bags, water bottles, straws, etc. There are some important applications of single-use plastics in terms of healthcare, but much of our single-use plastic items are created for convenience, not necessity. The less plastic used in this highly disposable manner, the less that it is likely to end up in our water.

We can also redesign the plastic we do use and its application to improve its recyclability. For example, many material recovery facilities cannot accept black plastic for recycling. So, why not make black plastic products, such as coffee cup lids or take-out containers, white to ensure they are recycled? Similarly, many products are designed where the plastic cannot easily be separated from other non-recyclable materials, meaning that the entire product will likely end up in landfill.

Secondly, we can improve our recycling systems. The Government of Canada estimates that only 11% of plastics are recycled in the country. To increase recycling, we need high recovery from the user – both consumer and industrial – back into the system.

Finally, there are low-cost ways individuals and businesses can reduce plastic going directly into waterways. Filters can be added to washing machines by the individual or the manufacturer to drastically reduce the plastic fibres, literally laundry lint, from entering the wastewater stream. Filters can also be applied to drains at factories to capture plastic particles from entering wastewater. Also, programs such as Operation Clean Sweep help manufacturers improve their processes and systems to prevent the potential introduction of plastic into the marine environment.

Other trash capturing technologies can be deployed in storm drains or at river mouths throughout our cities to reduce plastic entering water through urban runoff.

After decades of exponential growth of plastic use in North America we are just now beginning to understand the scope of the long-term problems that linear management of plastic pollution creates. Fortunately, we already know what many of the solutions are and new ideas and processes for building a circular economy are being developed locally and globally. If we have the will, the work ahead can implement the solutions.

Chelsea Rochman is an Assistant Professor in Ecology at the University of Toronto. To learn more about Dr. Rochman’s research, visit:

Watch Dr. Rochman’s presentation on plastic pollution in the Great Lakes, which was part of Partners in Project Green’s Breakfast Series. Learn more:


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