Microplastic pollution found in 100% of Delaware River tributaries tested

Fleece fragments in a washer flow into a wastewater treatment plant. A plastic bag blows into a stream. A water bottle washes down a storm drain.

All can end up in the region’s waterways as microplastics smaller than a grain of rice and find their way into drinking water and the stomachs of animals and fish.

This kind of microplastic pollution was detected in 22 stream and river segments across the Delaware River watershed, according to a new survey of waterways by the nonprofit advocacy group PennEnvironment Research & Policy Center.

Researchers analyzed water samples from sites along the Delaware River and its tributaries across Pennsylvania, New Jersey, Delaware, and New York.

The research was conducted in partnership with the nonprofit Environment New Jersey Research & Policy Center. Scientists with the Academy of Natural Sciences at Drexel University and the University of Pennsylvania helped analyze the results, which were released Wednesday during a news conference at Fairmount Water Works.

Contamination was found in the Delaware, Schuylkill, and Lehigh Rivers. It was found in Neshaminy Creek in Bucks County, Brandywine Creek in Chester County, and Cooper River in Camden County. And it was found along the Christina River in Delaware.

Drexel’s lab analysis confirmed microscopic plastic at every sampled site, highlighting what the researchers say is a widespread environmental threat.

“We can look at a waterway, and it might be free of litter, it might be free of visible plastic pollution, but that doesn’t necessarily mean it’s clean,” said Faran Savitz, an advocate for PennEnvironment. “The big takeaway is that we should be concerned. The depth, the breadth of this plastic pollution is staggering.”

Waterways in and around Philadelphia emerged as significant focal points in the survey results.

Samples drawn from the Delaware River in Philadelphia tested positive for multiple categories of microplastics including microfibers, microfragments, and microfilm, as did other waterways. Microbeads, often found in cosmetic products, were also found in the Christina River.

Microplastics are defined as fragments of less than 5 mm in length.

The synthetic microfibers came primarily from clothing and textiles. Rigid microfragments from items such as fishing line were found in 82% of locations. And flexible microfilm from bags and packaging appeared in 77%.

Researchers explained that laundering synthetic garments releases millions of microfibers that wastewater treatment facilities are unable to completely filter out before they are discharged into local streams.

However, because plastic does not biodegrade but continuously fractures into tiny fragments, filters capture only a portion of plastic entering a waterway.

Savitz said PennEnvironment’s study did not release the concentrations of microplastics because it did not want to compare one waterway or state against another.

The findings carry ecological and public health implications, as microplastics can block digestive tracts in wildlife and absorb toxic chemicals like PCBs and PFAS that bioaccumulate up the food chain, the report stated.

On average, humans ingest approximately 5 grams of plastic weekly, which is roughly equivalent to the weight of a credit card. Microplastics have been found in human blood, lung tissue, and organs, the researchers said.

Plastics are also routinely found in wildlife, including sea turtles, birds, and whales. About 60% of all seabirds have ingested plastic, with that number rising.

The environmental advocates are urging state and local leaders to enact policies such as producer responsibility for plastic packaging, bans on single-use foam and plastic bags, strict limits on pre-production plastic pellets, and enhanced drinking water filtration systems.

Microbeads once used in personal care products were phased out under President Barack Obama in 2015. But many of those products still linger on household shelves.

Philadelphians get their drinking water from the Delaware and Schuylkill rivers. Most microplastics are filtered out at PWD’s wastewater treatment plants, but some particles still get through.

In 2025, PWD removed 4.6 tons of plastic litter from the Delaware and Schuylkill rivers, alongside an estimated 1,000 tons of plastic extracted through sewer maintenance, the researchers stated.

PWD said in an online report that it is, “unclear whether microplastics pose a danger to human health,” noting that could depend on the level of exposure, the type of plastic, and the size of the particles.

But it notes that research suggests some are harmful to fish and animals and can build up in the organs or bloodstream over time.

“PWD is always investigating advanced treatment technologies that may eliminate microplastics and other impurities,” the report states.

David Velinsky, a senior scientist at the Academy of Natural Sciences of Drexel University, said, “plastics and microplastics are everywhere, from our clothing to the ubiquitous water bottle.”

When it’s not property disposed of or recycled, he said, it breaks down into ever smaller pieces.

“It can travel great distances through both the air and in the water,” Velinsky noted.

To combat pervasive plastics, advocates are urging federal and state lawmakers to enact targeted reforms, including the federal Plastic Pellet Free Waters Act currently before Congress, and state-level producer responsibility legislation for plastic packaging.

Savitz emphasized that shifting financial and operational burdens back onto manufacturers is critical to curbing waste at its source.

About seven states have passed producer responsibility laws, though not all are in effect, according to the Product Stewardship Institute. Those states include Washington, Oregon, California, Colorado, Minnesota, Maryland, and Maine.

“If we can shift the burden back onto companies that create this waste in the first place,” Savitz said. “We can actually reduce the waste, encourage recycling, and make these broader, more systemic changes.”