Researchers testing water across the Chesapeake Bay watershed found microplastic pollution at every single site they sampled, including five Maryland waterways stretching from Baltimore’s Patapsco River to the Chesapeake Bay itself in Talbot County. The researchers, who led the study for PennEnvironment Research and Policy Center, described the results as “jarring.”
According to CBS Baltimore, the study examined areas throughout the Chesapeake Bay watershed, which spans Maryland, Delaware, New York, Pennsylvania, Virginia and West Virginia and also receives flows from Washington, D.C. Researchers aimed to assess current microplastic levels in the watershed and their possible effects on the environment and on the people the bay serves. Microplastics, which measure less than 5 millimeters in length, form when larger plastic objects break down into smaller pieces in the environment, and researchers say their expansion is causing major pollution across oceans and waterways worldwide.
The research team collected and tested samples from the watershed for four types of plastic debris: fibers, fragments, film and beads. Per Baltimore Fishbowl, researchers collected six water samples each at 15 sites throughout the watershed between April 2024 and October 2026, and microplastics turned up at every one of them.
Fibers Topped the List at Every Site
Plastic microfibers, the kind shed from clothing and textiles, were the most common type of microplastic found, present at all 15 test sites, the Baltimore Fishbowl report notes. Researchers also found fragments, mostly from harder plastics or plastic feedstock, at 14 of the sites; film from bags and flexible packaging at seven sites; and beads, the kind used in facial scrubs and other cosmetic products, at four sites. CBS Baltimore’s figures frame the same pattern slightly differently, reporting microfibers in 100% of sampled waterways, microfragment material in 93% of areas, microfilm in about 47% of sampled areas, and microbeads in 27% of surveyed sites.
Five of the 15 sites were in Maryland: the Patapsco River in Baltimore, the Choptank and Nanticoke rivers in Dorchester County, the mouth of the Susquehanna River in Harford County, and the Chesapeake Bay itself in Talbot County, the same Baltimore Fishbowl account states. At all five Maryland sites, researchers detected both fibers and fragments, though film and beads turned up at none of them.
A Known but Poorly Measured Problem
The new findings build on years of incomplete data about plastic pollution in the bay. A 2019 workshop report from the Chesapeake Bay Program Scientific and Technical Advisory Committee acknowledged that researchers still had little idea of the magnitude and distribution of microplastics within the watershed. Earlier research cited by the Chesapeake Bay Program found microplastics in 59 of 60 samples collected from four tidal tributaries to the upper bay back in 2014, with concentrations highly correlated with urban or suburban land use.
A July 2024 monitoring framework addressed microplastics in the Chesapeake Bay watershed.
Why Most of the Plastic Never Leaves the Bay
Separate research adds an unsettling wrinkle to the bay’s plastic problem: much of what enters the watershed stays there. A 2021 Penn State modeling exercise, described by the Bay Journal, found that about 94% of microplastics running into the Chesapeake Bay and its tributaries never reach the ocean. The same outlet reported that tidal marsh sediment samples from the Darby Creek watershed showed microplastic presence increasing exponentially over the decades from the 1950s through the 2010s, except from 2000 to 2010, when there was no increase.
Scientists involved in the broader body of research have written that microplastics threaten environmental and public health, pose suffocation and starvation hazards to wildlife, and have been found in air, food and human bodies. The new study said more research is still needed to close gaps in understanding the full scope of human health effects tied to microplastic exposure.
Researchers Point to Policy Fixes
Americans generate an estimated 35 million tons of plastic waste annually, researchers said, yet only about 6% of plastic waste gets recycled. The study pointed to one policy lever already showing results elsewhere: states with bottle bills recycle about 60% of their beverage containers, compared with an average of about 24% in states without such laws, the Baltimore Fishbowl report notes.
The study urged federal, state and local leaders to reduce microplastic pollution by curbing single-use plastics and plastic packaging. Researchers specifically called on watershed states and their municipalities to phase out unnecessary single-use plastics, including polystyrene food-service products, plastic bags and utensils, in places where such policies don’t already exist. The study also proposed that states adopt producer responsibility laws shifting the burden of hard-to-recycle waste onto the companies that produce it, and urged Chesapeake Bay watershed states to approve bottle bills offering financial incentives for companies and consumers to recycle plastics. Researchers additionally urged Congress to expand producer responsibility for packaging and bottle deposit programs nationally, shifting pollution burdens onto polluters.
Not Just a Chesapeake Problem
The watershed’s plastic woes mirror what another PennEnvironment Research and Policy Center survey found just across the region. That study, reported by The Philadelphia Inquirer, found microplastic pollution in all 22 sampled stream and river segments across the Delaware River watershed spanning Pennsylvania, New Jersey, Delaware and New York. Drexel’s lab analysis confirmed microscopic plastic at every sampled site in that survey, with rigid microfragments from items such as fishing line found in 82% of locations and flexible microfilm from bags and packaging appearing in 77%.
