The Anacostia River is one of the most historically polluted waterways in the United States, running about 8.7 miles through Washington, D.C., before joining the Potomac River near the National Mall. For more than two centuries, the river has absorbed industrial waste, sewage overflows, and urban stormwater, leaving its sediments loaded with toxic chemicals and its ecosystem badly damaged. A large-scale cleanup has been underway since the early 2000s, combining sediment remediation, green infrastructure, and sewer upgrades, but the river’s recovery is complicated by ongoing contamination, invasive species, and deep inequities in who has borne the costs of living alongside a degraded waterway.
Two Centuries of Chemical Contamination
The Anacostia’s pollution story stretches back roughly 200 years, to a time when the river’s watershed was being rapidly converted from farmland and forest to industrial and residential uses. Sediment core studies show that a wide range of contaminants built up in the riverbed over that period, including polychlorinated biphenyls (PCBs), DDT compounds, chlordane, lead from gasoline, and polycyclic aromatic hydrocarbons (PAHs). Many of these chemicals peaked in concentration during the mid-to-late twentieth century and have been declining since their use was restricted or banned. PCBs, DDT, chlordane, and leaded gasoline additives all show clear drops that track directly to regulatory action. For other pollutants like PAHs and certain metals, the declines are more gradual and seem tied to shifts in industrial activity and waste management rather than outright bans.1PubMed. Historical contamination of the Anacostia River, Washington, D.C.
What makes the Anacostia’s contamination especially persistent is that many of these chemicals bind tightly to sediment particles. They do not simply dissolve and flush away. Instead, they settle into the riverbed, where they can be stirred up by storms, boat traffic, or dredging, re-entering the water column and food web decades after the original source was shut off. The river essentially carries a chemical memory of every factory, fuel spill, and pesticide application that ever touched its watershed.
Stormwater Is the Biggest Ongoing Problem
While historical industrial dumping created the contaminated sediment layer, the dominant ongoing source of pollution today is urban stormwater runoff. When rain hits the paved surfaces of Washington, D.C., it picks up oil, tire residue, heavy metals, and a soup of organic chemicals before draining into the Anacostia’s tributaries. The difference in contamination between dry weather and storms is dramatic. Sampling along six branches of the lower Anacostia found PAH concentrations in stormwater ranging from about 1,500 to 12,500 nanograms per liter, and the vast majority of those chemicals, between 68% and 97%, were bound to particles rather than dissolved in the water.2Environmental Pollution. Characterization of polycyclic aromatic hydrocarbons in urban stormwater runoff flowing into the tidal Anacostia River, Washington, DC, USA
The same pattern holds for PCBs. Stormwater entering the tidal Anacostia contained PCB levels up to 80 times higher than dry-weather base flow, and more than 90% of those PCBs were riding on particles.3Journal of Environmental Science and Health, Part A. Polychlorinated biphenyls in stormwater runoff entering the tidal Anacostia River, Washington, DC, through small urban catchments and combined sewer outfalls This is actually a useful finding for cleanup efforts, because it means that removing particles from stormwater before it reaches the river should substantially reduce the load of both PAHs and PCBs. The challenge is implementing that at a scale large enough to matter across an entire urban watershed.
Adding to the problem, Washington, D.C., still operates a combined sewer system in parts of the city, meaning stormwater and raw sewage flow through the same pipes. During heavy rains, the system overflows directly into the Anacostia, sending untreated sewage, nutrients, and trash into the river. A massive underground tunnel project, the Anacostia River Tunnel System, has been built to capture and store these overflows so they can be treated at the Blue Plains wastewater plant instead. But combined sewer overflows represent just one piece of the puzzle; even separated stormwater, which never mixes with sewage, carries its own heavy chemical load.
What the Fish Tell Us
One of the most striking indicators of the Anacostia’s contamination has come from studying brown bullhead catfish, a bottom-dwelling species that feeds directly on organisms living in contaminated sediments. Researchers examining bullheads from three Anacostia locations found liver tumor rates between 50% and 68% among adult fish, and skin tumor rates between 13% and 23%. Elevated levels of PAH-related metabolites and DNA damage markers were found in bullheads of all sizes, providing strong evidence that the tumors were linked to chemical exposure rather than some other cause.4Environmental Toxicology and Chemistry. Tumor prevalence and biomarkers of exposure and response in brown bullhead (Ameiurus nebulosus) from the Anacostia River, Washington, DC and Tuckahoe River, Maryland, USA
The encouraging side of this story is that follow-up surveys conducted in 2014 through 2016 found liver tumor rates had dropped. The researchers attributed the decrease to falling levels of PAHs, PCBs, and DDT compounds in the sediments, as measured by biomarker and tissue analyses of the fish themselves.5PubMed. Trends in Liver and Skin Tumor Prevalence in Brown Bullhead (Ameiurus nebulosus) from the Anacostia River, Washington, DC, and Nearby Waters Brown bullheads are useful sentinels precisely because they live in close contact with sediment, so changes in their health tend to reflect real shifts in the chemical environment. The declining tumor rates suggest that regulatory bans and reduced industrial activity are showing measurable biological effects, even if the river is far from clean.
Nutrient Overload and Summer Oxygen Crashes
Toxic chemicals get most of the headlines, but the Anacostia also has a severe nutrient pollution problem. Excess nitrogen and phosphorus from fertilizer runoff, sewage overflows, and atmospheric deposition feed heavy algal growth, especially during warm months. Water quality monitoring found that nutrient concentrations in the Anacostia are well above the levels that typically trigger excessive algae growth under all flow conditions. The consequences are seasonal but severe: summer chlorophyll a concentrations averaged about 27 micrograms per liter, nearly double the spring average, and the summer algal community was dominated by cyanobacteria rather than the diatoms that make up more of the spring community.6Environmental Monitoring and Assessment. Chesapeake Bay’s “forgotten” Anacostia River: eutrophication and nutrient reduction measures
When those dense summer blooms die and decompose, bacteria consume dissolved oxygen, creating hypoxic conditions that can suffocate fish and other aquatic life. The Anacostia’s shallow depth, slow tidal flow, and high nutrient loads make it especially prone to these oxygen crashes. In a river already stressed by chemical contamination, summer hypoxia adds another layer of pressure on species trying to survive and reproduce. This is why many ecological assessments describe the Anacostia as one of the most degraded urban rivers in the Chesapeake Bay watershed.
Cleanup Strategies on Multiple Fronts
Restoring the Anacostia requires attacking the problem from several directions at once: capping or removing contaminated sediments, reducing stormwater pollutant loads, controlling sewer overflows, and rebuilding habitat. Each approach targets a different part of the contamination cycle.
On the sediment side, a demonstration project tested “active capping,” which involves placing engineered materials over contaminated riverbed to physically isolate pollutants and chemically bind them in place. The Anacostia capping trial successfully placed three types of materials: a low-permeability clay composite to seal the sediment surface, apatite (a calcium phosphate mineral) to absorb metals, and coke (a carbon-rich material) to absorb organic pollutants like PAHs.7Remediation. Active Capping Demonstration in the Anacostia River, Washington, D.C. The idea is not just to cover the contamination but to create a reactive barrier that keeps chemicals from migrating upward into the water. Active capping is less disruptive than dredging, which can actually resuspend contaminants during the removal process, but it requires the cap to remain intact over time, which is not guaranteed in a tidal urban river subject to flooding and erosion.
On the stormwater side, the District of Columbia has invested heavily in green infrastructure, which uses natural systems to absorb and filter runoff before it reaches the river. The District Department of Energy and Environment identified four sub-watersheds within the Anacostia basin for retrofitting with more than 40 individual green infrastructure installations, including bioretention cells, permeable pavement parking lanes, permeable-pavement alleys, and expanded green spaces. The design philosophy uses a “treatment train” approach, chaining multiple practices together in series and combining them with reductions in paved surface area to maximize pollutant removal.8Access Water. Innovative Methods to Select and Implement Green Infrastructure Improvements within Large Watershed Areas Because both PAHs and PCBs travel primarily on particles in stormwater, filtering out suspended solids upstream of the river should meaningfully cut the delivery of these chemicals.9Journal of Environmental Science and Health, Part A. Polychlorinated biphenyls in stormwater runoff entering the tidal Anacostia River, Washington, DC, through small urban catchments and combined sewer outfalls
The tunnel system designed to capture combined sewer overflows represents the city’s largest single infrastructure investment in the river. When fully operational, it should dramatically reduce the volume of raw sewage reaching the Anacostia during storms. But tunnels alone cannot solve the nutrient problem, because much of the nitrogen and phosphorus load arrives through separated stormwater and atmospheric deposition rather than through sewer overflows.
Environmental Justice and the Divided River
The Anacostia is not just an environmental problem; it is a case study in who bears the burden of urban pollution. Washington, D.C., has long been a city with a stark geographic divide, and the Anacostia River sits at the center of it. Neighborhoods east of the river are predominantly Black, lower-income communities that have historically received less public investment, worse infrastructure, and more exposure to industrial pollution than areas west of the river. The river’s degradation and the decades of neglect that allowed it are inseparable from this history of racialized disinvestment.
Since the early 2000s, the Anacostia Waterfront Initiative (AWI) has worked to revitalize the river and its surrounding neighborhoods. Researchers who examined the initiative through interviews, planning documents, and site visits found that it attempted to address both social and environmental justice, aiming to clean up the river while also improving economic opportunity and housing access in east-of-the-river communities. But the study also found contradictions between these goals: waterfront redevelopment that raises property values and attracts new businesses can also displace the low-income residents who lived with the river’s contamination for decades and who stand to benefit most from its recovery.10Urban Affairs Review. Social and Environmental Justice in Waterfront Redevelopment: The Anacostia River, Washington, D.C.
Gentrification pressure along the Anacostia waterfront is real and growing. New mixed-use developments, parks, and trails make the area more attractive, which is the goal from an environmental standpoint but carries economic consequences for existing residents. Whether the cleanup ultimately serves the people who lived with the pollution or primarily benefits newcomers is one of the sharpest questions hanging over the entire restoration effort.
Subsistence Fishing and Ongoing Health Risks
Despite fish consumption advisories that have been in place for years, people still fish the Anacostia for food. Anthropological fieldwork along the river has documented a community of subsistence fishers who regularly catch and eat fish from its waters. For these individuals, the Anacostia is not an abstraction or a symbol; it is a food source. They set lines and clean their catch in a river where roadway runoff, sewer spillage, trash, and legacy industrial contaminants like PCBs remain embedded in the sediment and can accumulate in fish tissue.11Journal for the Anthropology of North America. Encounters with the Flesh of Fish: Subsistence Fishing along the Anacostia River
This creates a direct human health exposure pathway. Chemicals like PCBs and DDT compounds bioaccumulate, meaning they build up in the tissue of organisms as you move up the food chain. A person regularly eating catfish or other bottom-feeders from the Anacostia could be taking in meaningful doses of contaminants that have been declining in the sediment but have not disappeared. The fish advisory signs posted along the river assume that people will read them, understand them, and have alternative food sources available, which is not always the case for subsistence fishers.
Invasive Blue Catfish as an Ecological Complication
As if legacy contamination, stormwater pollution, and nutrient overload were not enough, the Anacostia and its connected Chesapeake Bay tributaries face a growing invasive species problem. Blue catfish, originally introduced to a few Virginia tributaries in the 1970s and 1980s for sport fishing, have expanded throughout the tidal Chesapeake region. These are large, aggressive, generalist feeders that eat everything from invertebrates to vegetation to other fish.
Their spread has had cascading effects on native species. White catfish populations have declined in areas where blue catfish have established themselves, likely due to direct competition for habitat and food. More concerning from a conservation standpoint, blue catfish prey on alosines, which include American shad, blueback herring, and alewife, species already in trouble due to decades of overharvesting and habitat loss along the Atlantic coast. Blue catfish eat migrating alosines primarily in spring, when shad and herring run upriver to spawn. While alosines appear in only a small fraction of individual blue catfish stomachs, the sheer number of blue catfish in these systems means the total predatory impact could be substantial.12North American Journal of Fisheries Management. Invasive Blue Catfish in the Chesapeake Bay Region: A Case Study of Competing Management Objectives
Managing blue catfish is further complicated by the fact that they have become economically valuable. A commercial fishery has developed around them, and some fisheries managers worry that aggressive removal efforts could conflict with the interests of commercial harvesters who now depend on the species. For the Anacostia specifically, blue catfish represent yet another stressor on a system that is trying to recover from chemical contamination and habitat loss simultaneously. Restoring native fish communities means dealing not just with water quality but with a food web that has been fundamentally altered by a species that was never supposed to be there.
How Far the River Has Come and What Remains
The Anacostia’s trajectory is genuinely mixed. Sediment data show that many of the worst contaminants have been declining for decades, driven by bans on chemicals like PCBs and DDT and by gradual improvements in waste management.13PubMed. Historical contamination of the Anacostia River, Washington, D.C. Fish tumor rates have dropped as those contaminant levels have fallen.14PubMed. Trends in Liver and Skin Tumor Prevalence in Brown Bullhead (Ameiurus nebulosus) from the Anacostia River, Washington, DC, and Nearby Waters Billions of dollars in infrastructure investment are being directed at sewer overflows and stormwater management. Green infrastructure is being installed at meaningful scale across the watershed. These are real, measurable improvements.
But the river still has nutrient levels that fuel toxic algal blooms every summer. Stormwater from one of the most densely paved cities in the country continues to deliver fresh loads of chemicals with every rainstorm. Legacy contaminants in the sediment will take decades more to fully attenuate, even with active capping and natural recovery. The communities most affected by the river’s degradation face the risk of being priced out of the neighborhoods that their presence helped build. And invasive species are reshaping the food web in ways that no amount of chemical remediation can fix on its own. The Anacostia is getting cleaner, but “cleaner” and “clean” are very different things in a river this compromised.