Microplastics are pervasive throughout the Chesapeake Bay watershed, and they could have damaging effects on the health of humans and animals across the region, according to a new study.
The consumer advocacy nonprofit Maryland PIRG released the study Tuesday on behalf of its sister group, Environment Maryland Research & Policy Center. The center tested for the presence of microplastics, which measure less than 5 millimteres long (smaller than a grain of rice), in the Patapsco River and across the multi-state Chesapeake Bay watershed, including samples from Maryland, Pennsylvania, New York, and the District of Columbia.
Researchers collected six water samples each at 15 sites throughout the Chesapeake Bay watershed from April 2024 to October 2026. The study found microplastics at every site.
“[W]hile environmental laws and restoration efforts have reduced some pollution threats to the watershed and restored some of its waterways to health, a range of new threats—from pharmaceuticals and microplastics to pollution from factory farms and the dangers posed by fossil fuel production and transportation—threaten the progress we have made,” the report’s authors write.
Plastic microfibers, such as from clothing and textiles, were the most common type of microplastics, found at all 15 test sites.
Researchers also found fragments, primarily from harder plastics or plastic feedstock, at 14 of the sites; film, including from bags and flexible plastic packaging, at seven sites; and beads, like those used in facial scrubs and other cosmetic products, at four sites.
Five sites in Maryland were part of the study: 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 in Talbot County.
Of the samples taken in Maryland, fibers and fragments were detected at all five sites, though film or beads were found at none.
Advocates are troubled by the widespread presence of microplastics.
Research from the University of Newcastle in Australia estimated the average person could be consuming 5 grams of plastic every week – equivalent to a credit card.
Other studies report microplastics have been found in human kidneys, livers, lungs, blood, brains, and even in fetuses.
Meanwhile, the National Oceanic and Atmospheric Administration has found microplastic particles can attract heavy metals and chemical contaminants that are then consumed by fish, birds, humans, and other organisms.
“Not enough is known about the full effects of microplastics in humans, but chemicals related to plastic can cause endocrine disruption, hormonal effects, and reproductive disorders,” according to the Chesapeake Bay study.
Although microplastics have become practically inescapable, the challenge is not irresolvable.
The report’s authors recommend several policy changes at the local, state, and federal level to curtail the effects of microplastics, such as reducing single-use plastics and plastic packaging; addressing pollution from plastic pellets, or “nurdles”; and reducing textile waste and the use of synthetic plastic fibers.
“Nothing society uses for a few minutes should be able to pollute our environment for hundreds of years,” the authors write.
Other recommendations include opposing plastics incineration; fighting environmental rollbacks; reforming recycling systems; filtering out toxic contaminants and eliminating PFAS, also known as “forever chemicals,” from being added to products in the first place; and having governments and corporations set an example by implementing better policies for procurement.
“Producer responsibility is a mechanism to shift the costs and management of postconsumer waste from local governments and consumers and onto producers themselves, requiring producers of plastic products to design, manage, and finance waste and recycling programs for plastic packaging,” according to the authors.
The researchers advocate for Chesapeake Bay Watershed states to pass “bottle bills,” which would allow consumers to return empty plastic, metal, and glass beverage containers to participating retailers in order to be refunded a small deposit.
So far, efforts to pass such a bill in Maryland, including during this year’s legislative session, have failed.
But the 10 states that have a bottle bill on the books recycle about 60% of their beverage containers, compared to states without one which average about 24%.
Curious about microplastics and other contaminants in your local waterway? You can use the Environment Maryland Research & Policy Center’s guide to conduct your own test.
