Plastic and other waste floats on the Marine Lake at New Brighton beach, near Liverpool, Britain, on Feb. 11, 2019.Phil Noble/Reuters
Plastic pollution is more concentrated in some lakes and reservoirs around the world than in the infamous “garbage patches” of the Pacific and Atlantic oceans, according to a study published in the scientific journal Nature on Wednesday.
The study found that plastic waste from items such as clothes, water bottles and car tires has infiltrated every corner of the globe. The research, led by scientists at the University of Milan-Bicocca, involved sampling bodies of water in many different places. Among the lakes and reservoirs tested, some of the highest concentrations of microplastics – small plastic pieces less than five millimetres long – were in some main sources of drinking water, such as Lake Tahoe in the United States and Lake Maggiore in Italy. In these locations, microplastics exceeded concentrations in the subtropical oceanic gyres, such as the one known as the Great Pacific Garbage Patch, a mass of waste twice the size of Texas.
The Canadian lakes included in the study, Ontario’s Plastic Lake (the name is a coincidence) and Dickie Lake, showed lower concentrations of plastic than Tahoe, which is located next to a number of towns and cities. But Plastic Lake, a comparatively remote body of water with no homes nearby and little other human contact, still had plastic debris.
“Microplastics are everywhere,” said Brittany Welsh, a PhD student at Trent University who sampled Plastic and Dickie lakes for the study. “We may not think they’re everywhere, but they’ve reached pretty much every corner of Earth at this point.”
Scientists are hoping this research will begin a new chapter in understanding plastic pollution, the health effects of which on humans and wildlife are still being studied and debated.
Over 400 million tonnes of plastic is produced each year worldwide, half of which is for single-use items. So far, studies have focused on the plastic that ends up in the ocean, forming islands of trash, such as the Pacific garbage patch.
But this study shows that plastic pollution is not just an ocean problem.
Julian Aherne, a professor at Trent University and one of the study’s co-authors, said this was the first globally comparable research on plastic in inland water bodies. “The methods for sample collection and analysis for the Canadian lakes are the same as those for the Italian lakes, so we can directly compare the results,” he said. “More importantly, we can use these data to ask questions such as, ‘What drives the abundance in lakes?’”
Researchers used large, cone-shaped plankton nets that were dragged horizontally through the water by boats. The resulting samples were sent to the University of Milan-Bicocca, where they were analyzed using Raman micro-spectroscopy, a technique that involves shooting lasers at an object to examine its chemical composition.
Microplastics are fragments that come from a variety of sources, such as synthetic clothing, tires and single-use water bottles. The particles evade water filtration systems, entering lakes and oceans. They can also be picked up by wind, which can carry them thousands of kilometres before they fall to the ground when it rains. Because microplastics are so small and so ubiquitous, humans and animals are constantly ingesting them.
Plastics can take anywhere from a decade to thousands of years to decompose. Researchers believe the microplastics found in lakes right now were mostly manufactured in the 1950s, and have taken this long to break down. Plastic production has increased dramatically since then.
“The microplastics we see today are from the breakdown of legacy plastics in the environment,” Dr. Aherne said. “So if all plastic production and use stopped today, we would still see an exponential increase in microplastics in the environment as the current waste plastics break down.”
The high concentrations of plastics in lakes come as no surprise to Jennifer Provencher, a wildlife researcher at Carleton University who focuses on the impacts of contaminants on wildlife. She was not involved in the study.
“We have this general perception that pollution is this offshore, middle-of-the-ocean problem,” Dr. Provencher said. “It’s not just an offshore problem. It is very much a land problem, a lake problem, a freshwater ecosystem problem as well. We just haven’t looked very hard at it.”
She noted that it is hard to accurately compare the different concentrations of plastic in freshwater and saltwater ecosystems. Some parts of the ocean are more polluted than some lakes, and vice-versa.
Dr. Provencher said the next step is gathering more data.
“This is probably the first, broad glimpse at the 30,000-foot level,” she said of the study. “It is indicating that there is pollution. And it sounds like it could be as polluted as some of our oceanic regions.”
She said further studies will be more specific. They could include comparing pollution across latitudes, watersheds and watershed use, and could also look at plastic pollution in different ecosystems, and the impacts of activities such as human water sports.
Dr. Aherne is hoping that this new study will expand thinking on microplastics, and move public conversation on the topic beyond ocean pollution.
“We need to shift our focus from marine, towards a microplastic cycle perspective, looking at all sources, pathways and receptors in the cycle,” he said.