Microplastics Lurk in Freshwater Environments Across Pennsylvania

March 24, 2025

By Kiley Bense, Inside Climate News

This article originally appeared on Inside Climate News, a nonprofit, non-partisan news organization that covers climate, energy and the environment. Sign up for their newsletter here.

PHILADELPHIA—At the John Heinz National Wildlife Refuge visitors center, a sculpture of a great blue heron made from recycled plastic bottles greets guests. Standing 12 feet tall, the bird draws attention to the problem of plastic pollution in the refuge and surrounding city.

In a recent study, scientists at Penn State University revealed the more insidious side of plastic pollution at the 1,000-acre refuge, an urban oasis known as a birders’ haven. After analyzing sediment samples taken at Heinz and three other watersheds across Pennsylvania, the study found increasing levels of microplastics from the 1950s to the 21st century, consistent with the boom in worldwide plastic production that continues today.

The data shows that freshwater sediment acts as a “sink” for microplastics to accumulate over time. Microplastics are small plastic particles, less than 5 millimeters across, that are manufactured for specific products or created when larger plastic products break down.

Lisa Emili, an associate professor of environmental studies at Penn State Altoona and a co-author of the study, said the results were surprising. Emili said she was not expecting to find microplastics in the samples taken from a reservoir in rural central Pennsylvania.

“On one hand it was like, ‘Yes, we’ve got the procedures right, and we have results. We found microplastics.’ And then on the other hand, it was like, ‘Oh no, we found microplastics where we thought there would be no contamination, this is horrible,’” Emili said. “I still feel that way every time I look in my microscope and see these things. They’re everywhere.”

Emili said microplastics can contain toxic chemicals themselves, and they can also serve as vehicles for other pollutants. “You can have hitchhiker pollutants that attach themselves to the microplastics,” she said, which are then consumed by fish and other aquatic wildlife and can travel up the food chain.

“At the most basic level, fish will ingest microplastics, and they will feel full,” Emili said. “So there have been examples of fish starving, essentially because they think they’ve eaten.”

This has negative implications for animals that depend on the fish as a food source. Research shows microplastics can interrupt animals’ life cycles, disrupting reproduction and affecting cellular functioning, she said. Scientists are currently studying the impacts of accumulating microplastics in humans, and recent research has found microplastics in people’s brains, blood, lungs and kidneys, but this is an emerging field of study and much remains unknown.

Emili said the research team had to be vigilant about warding off cross-contamination—using glass and steel equipment, and wearing cotton lab coats—because of the ubiquity of microplastics in the environment. When one student assisting her in the lab wore a sweatshirt instead of a lab coat, bright fibers from the synthetic material ended up in the samples.

This is why it’s so difficult to get rid of microplastics: So many of the products we use daily are constantly shedding them.

The John Heinz refuge regularly hosts plastic litter cleanup events, and since 2020, it has supported a plastics committee formed to raise awareness about the issue.

“Doing cleanups at the refuge has really opened my eyes,” said Carol Armstrong, the founder of the plastics committee and a board member for Friends of Heinz Refuge, a nonprofit that collaborates with the U.S. Fish & Wildlife Service to care for the refuge. “The first time you do this, it’s so shocking.”

Once, she said, she went to an island in the refuge that hadn’t been cleaned before. “There were layers of plastic objects, at least six to eight inches thick, embedded in the reeds and the roots.”

Despite these efforts and some visible signs of progress, volunteers at the refuge worry about the long-term effects of microplastics on the plants and animals and the site’s ability to cope with such a tiny and persistent form of pollution.

Jaclyn Rhoads, another board member who has been involved in cleanups for years, said collecting and disposing of plastic bottles and bags is different than trying to clean up seven decades’ worth of microplastics. “It just seems impossible. It lingers for a long, long time,” she said.

Rhoads fears microplastics could become a “new DDT,” the notorious pesticide that Rachel Carson wrote about in “Silent Spring.” In addition to 122 species of birds, the refuge is home to a nesting pair of bald eagles, a popular draw for birding groups. Bald eagle populations were devastated by exposure to DDT in the 20th century and have only recently begun to recover.

“With the number of species that have started to come back at the refuge, this is a really critical time for us to pay attention to plastic pollution,” Rhoads said. “Although the refuge can obviously do cleanups and we can provide education, at the end of the day, this really has to come from a higher level.”

Given the expense and uncertainty associated with removing microplastics from any environment, the most effective remedy, experts say, is to stop dumping so much of them into our waterways in the first place. That would include decreasing single-use plastic production and better regulating the treatment and discharge of wastewater. Plastics manufacturing companies oppose policies that would reduce production, and the amount of plastic waste generated in the United States has risen from 390,000 tons in 1960 to more than 35 million tons in 2018.

The Penn State researchers were not expecting the samples from the John Heinz refuge to have lower concentrations of microplastics than the other samples, because the refuge is in an urban and densely populated area. Emili said the finding may be attributable to the fact that Darby Creek is a tidal estuary, and some of the microplastics passing through the creek are being carried out to the ocean rather than settling there.

Emili said the researchers are now working on determining what kinds of plastic they found to better pinpoint the sources of pollution, building on the work they’ve already done to date the samples using radioactive decay.

The one “uplifting” result from the study was a slight decrease in the concentrations of microplastics in the samples after 2010. Emili said this could be due to an increase in recycling in this period. “That obviously requires more study,” she said. “But it’s also somewhat heartening to understand that we can make changes that will make a difference.”