How Toronto’s combined sewers release flushed plastic wet wipes directly into aquatic ecosystems
When I started working as a research assistant in the Rochman Lab, I never could have imagined what my first job would be: managing used, littered plastic items pulled directly from the Don River. I worked on a project called “Plastics Spiraling in River Networks” (pSIREN), and every day I was measuring, counting, and testing many kinds of littered items, from plastic bags and food wrappers to menstrual products and clothing. But the most surprising item, to me, were the wet wipes. These hard, stringy, dirt covered balls fished directly from the Don River hardly resembled wet wipes at all. It made me curious about why and how they ended up in the Don River, so as a Pollution Prevention Project Fellow I proposed to lead a new U of T Trash Team Pollution Prevention Project on this prevalent source of plastic pollution, which we dubbed “Wipes vs Pipes”.
Wipes vs. Pipes aims to understand and quantify the fate of plastic wet wipes in the Don River to inform possible solutions to wet wipe pollution. Using data from pSIREN, I found that wet wipes made up 25% of all plastic litter in the Don River! Furthermore, I tested these wet wipes using infrared spectroscopy to determine what material (e.g., plastic, cotton) they were made of.
I found that 99% of the littered wet wipes in the Don River were plastic: either polyester or polypropylene. I also discovered that most of the wet wipe pollution was found at sites downstream of combined sewage overflow. In Toronto, during periods of heavy precipitation, the contents of sewage pipes are diverted (away from wastewater treatment plants) to nearby rivers and streams. This is to prevent wastewater treatment plants from hitting capacity and backing up. This means that all untreated flushed material, like sewage waste and plastic hygiene products, are released into aquatic environments. Wipes vs. Pipes estimates that there are at least 64,000 wet wipes in the Don River at any time.
So, we knew how plastic wet wipes were entering the environment and to what scale. But the next question was, why?
Why were so many plastic wet wipes being flushed down the toilet when they should be placed in the waste bin?
To answer this question, I visited supermarkets to see how clearly wet wipe packages mentioned anything about how to throw away used wet wipes. I also checked packages for information regarding wet wipe material – since not many people think about what wet wipes are made of (prior to my work on pSIREN, I didn’t!). I checked every section I thought I might find a wet wipe package: home cleaning, cooking, makeup, pet care, babies, kids, and more. In one store, some “flushable” wet wipes were actually advertised in the toilet paper section!
Unsurprisingly, only 7 of 72 wet wipe packages mentioned what the wipes were made of, and 33% of wet wipe packages lacked any kind of disposal information at all. Of the 67% of packages that did contain disposal instructions, the information was not always highly visible. That means a “do not flush” logo or the written “Do not flush” instructions would often be on the back of the package, in small font, in a low-contrast colour to the background, or anything else that hindered visibility to the consumer. Because some wet wipes are “secretly” plastic, consumers might not know that they shouldn’t be flushed.
Now we knew how wetwipes were entering the Don River, and why they were flushed in the first place. My last question concerned the fate of those flushed wet wipes.
What happens to a wet wipe after it enters the environment?
During a mostly crisp and sunny October, we set up an experiment on the greenhouse roof of the Earth Sciences building at the University of Toronto St. George Campus to see how different kinds of wet wipes break down over time. It was a little funny to see this greenhouse roof filled with beautiful, diverse plants and pollinators, with my wet wipe experiment nestled in a corner. We prepared jars of three different wet wipe polymer types, two plastic (polyester and polypropylene) and one flushable material (cellulose), and exposed them to conditions that would mimic those in the Don River. Some jars were kept in the dark to mimic shade, some always in the sun; some jars had water in them and some were dry (e.g., mimicking whether the wet wipes were littered on the dry banks or in the water); and some of the jars with water were mixed on a shaker table to emulate the moving river.
After two and six weeks, we counted microfiber shedding and weighed the wet wipes, and found that some material types shed more microfibers than others. As expected, the flushable material broke down much more readily than either of the plastic wet wipes, although they did still shed microfibers. Between the two plastic polymers, polypropylene wipes shed more microfibers than ones containing polyester. So, there’s a difference in microplastic generation within wet wipe types! Additionally, we saw all wet wipes shed microfibers more readily when exposed to water than when they were dry. Ultimately, we found that all wet wipes (both plastic and non-plastic) can break down into microfibers when flushed down the toilet. And, that these microfibers may be created in sewage pipes, or when wet wipes are released in nearby rivers and streams.
How can we solve plastic wet wipe pollution?
Luckily, there are many ways to tackle plastic wet wipe pollution. The simplest way is to always throw used wet wipes in the garbage!
For solutions at a larger scale, I was able to interview wet wipe experts across industry, policy, and wastewater plants to ask them what they thought Canada should do. Three policy suggestions were the most popular. The first is to mandate clear “do not flush” labelling on all non-flushable wet wipe packages. The second is to enforce the testing of all “flushable” wet wipes through the International Water Services Flushability Group (IWSFG), to ensure that they are really flushable. The final policy suggestion is to ban plastic wet wipes, which meet the criteria under Canada’s Single Use Plastics Ban.
Tackling plastic pollution can be daunting. Which is why, in addition to engaging stakeholders, I focused on engaging my local community! I designed visual aids, like social media campaigns, an infographic, and postcards and stickers to make my findings more accessible to the public. Summaries of my project findings are also available through our policy brief and public webinar. When we all work to raise awareness through science, stakeholder engagement and community outreach, we can tackle plastic pollution together.
Blog written by Simran Hansra, a master’s student in the Department of Ecology & Evolutionary Biology at the University of Toronto, and a Pollution Prevention Fellow with the U of T Trash Team.