While we know more than ever about how tiny plastics are moving through the Great Lakes and the atmosphere, there are still questions on how they affect wildlife and people.
That’s according to Dr. Sherri Mason, a professor of chemistry and sustainability coordinator at Penn State Behrend, who gave a virtual plenary talk at the 2021 International Association for Great Lakes Research conference in May.
“Enough plastic has been produced to cover Argentina ankle deep,” Mason said. “Of that, only 11 percent has been recycled, 15 percent has been incinerated and maybe a third of it is still in use. The rest has been lost to the environment.”
Plastic pollution is incredibly abundant in the Great Lakes, with lakes Michigan, Erie and Ontario bearing the brunt. A 2016 study from the Rochester Institute of Technology found that 10,000 metric tons (22 million pounds) of plastic enters the Great Lakes every year.
In 2017, the IJC released a report on microplastics in the Great Lakes with recommendations for actions to reduce the amount of plastics getting into the water.
The report recommended further research on how and where plastics were moving into and around the lakes and an assessment of ecological and human health impacts. It also recommended that Canadian and US governments adopt policies to reduce plastic debris in the aquatic environment, including promoting life-cycle responsibility to producers. Additionally, IJC recommended that the federal governments provide funding and support for local efforts to provide education and outreach to reduce plastic debris in the Great Lakes. Since the report, new laws on both sides of the border have phased out microplastics in consumer goods like soaps and cosmetics, with state governments looking at new policies that make producers responsible for recycling or disposing of their goods.
Mason explained that surveys performed over the past decade found that most of the plastics in the Great Lakes are fragments – made up predominantly of cigarette butts. Plastic fibers, such as those found in synthetic clothing materials, are the predominant type of plastic found in Lake Superior, while lakes Erie and Ontario also contain a substantial number of pre-production pellet fragments produced at chemical plants around Sarnia. In all cases, about 75 percent of these plastic pieces are smaller than 5 millimeters (about 0.2 inches).
The Great Lakes are part of a connected system, which means that rivers, smaller lakes and tributaries also have microplastics within them.
Mason said that working with US Geological Survey, researchers sampled 29 tributaries that accounted for 22 percent of the water flowing into the Great Lakes. These all have different land uses, land cover, water treatment systems and population densities, but they all had microplastics in common. The greatest amount of plastic fragments were found in urban areas with higher-than-average water flows in tributaries.
Researchers found a consistent amount of plastic fibers in all the areas sampled. However, Mason said one of the “knowledge gaps” not studied is where these fibers are originating from or to what degree they’re being carried by water, through the atmosphere or coming from stormwater or wastewater. Mason hypothesized that turbulence in tributary rivers keeps the fibers afloat, but once they enter the Great Lakes they sink to the bottom; a study done in the Milwaukee River basin in 2019 appears to back up this idea, she added.
As these fibers continuously enter the lakes, what impact are they having on fish, birds, and people?
Mason cautioned that the answer is not clear. She referred to a of the Chicago Field Museum that looked at archived fish tissue samples going back to 1900. It found that plastics started appearing and significantly increasing in samples from 1950 up through 2018. Other studies found plastic fragments in mussels and attached to algae.
“When this algae dies seasonally, the microplastics redeposit in the sediment or are resuspended into the water,” Mason said.
Mason was recently involved in two studies regarding plastic sources and how prevalent plastics are in things humans eat and drink. One of these found bottled water, followed by beer, had the highest amounts of plastic, while the other looked specifically at bottled water sourced from around the globe with similar results. A great deal of plastic fibers also are being carried in the atmosphere, before being deposited elsewhere.
A 2019 analysis by the World Wildlife Fund estimates the average person ingests a credit card’s worth of microplastics per week – largely through drinking water and air. A 2020 study found that microplastics are a potential vector for chemical contaminants.
Finally, Mason noted that there are still knowledge gaps on plastic degradation, health impacts from plastics consumption and the breakdown of newer biodegradable plastics. There has been research over the years indicating that microplastics contribute to suffocation, starvation and injuries of animal life, though these have largely taken place in laboratories using higher concentrations than those found in the open lakes. As a result, there are still questions as to the effects of larger pieces of plastics in lesser concentrations, as well as how these may affect the broader, complex ecosystems in the Great Lakes.
Kevin Bunch is a writer-communications specialist at the IJC’s US Section office in Washington, D.C.