The most polluted rivers in the United States are the ones that receive the largest volumes of industrial toxic discharge, nutrient runoff and untreated sewage — and by the federal government’s own accounting the Ohio River leads the list, taking in roughly 41 million pounds of toxic chemicals in 2020, more than any other watershed in the country. Nationally, the U.S. Environmental Protection Agency’s most recent National Rivers and Streams Assessment found 47% of river and stream miles in poor biological condition.
Rivers are one of the most important water sources for drinking water and other natural resources for us like fish. And it plays a big part in maintaining biodiversity. It serves as a natural habitat for hundreds of freshwater species like salmon, mussels, crabs, frogs, turtles, freshwater snails, and many more. However, for several decades, the human population has been affecting rivers because of improper and irresponsible disposal of different kinds of waste, causing these rivers to get polluted.
Too much pollution can be detrimental to the ecosystem because it kills fish and other wildlife dependent on the river. Pollution such as garbage, sewage, oil spills leads to land erosion and many others faster than usual.
Sometimes we could see the remains of this pollution remaining in the river like styrofoam, plastics, and other wastes that we throw away.
What makes a river polluted?
A polluted river can be defined as a water body that contains components that result in contaminated water quality, which is not suitable for drinking or other natural resource utilization due to the presence of pollutant substances like hydrocarbons, solvents, sedimentation.
Unfortunately, most rivers and oceans are already suffering from different kinds of pollution caused by a variety of wastes, mostly through industrial operations and incorrect garbage disposals.
Causing poison and loss of oxygen to these rivers, resulting in the destruction of natural inhabitants and the loss of natural resources for us humans.
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How the most polluted U.S. rivers are actually ranked
There is no single official “dirtiest river” league table. Three separate federal and non-profit datasets are what serious rankings are built from, and they measure different things.
EPA Toxics Release Inventory (industrial discharge by weight)
Industrial facilities must report what they release to water under the EPA’s Toxics Release Inventory. Environment America’s Wasting Our Waterways analyses of that data are the reason the Ohio River is repeatedly named the most polluted river in America by discharge volume: roughly 41 million pounds of toxic chemicals entered the Ohio River Basin in 2020, more than any other U.S. watershed. The Ohio also receives the greatest volume of cancer-causing chemical discharges of any American river.
Clean Water Act impaired-waters lists (legal status)
Under section 303(d) of the Clean Water Act of 1972, states must list water bodies too polluted to meet their designated uses — swimming, fishing or drinking-water supply. A river appearing on a state’s 303(d) list is legally “impaired,” which is a far more precise statement than calling it dirty.
America’s Most Endangered Rivers (threat, not filth)
The conservation group American Rivers publishes America’s Most Endangered Rivers every spring. It ranks rivers facing a decision point in the year ahead rather than the ones already worst polluted. The 2026 report, its 41st, named the Potomac River number one, citing a historic sewage spill and the water demands of rapid data-centre growth across the watershed; the San Joaquin River in California placed second.
Most Polluted Rivers in the United States
Most countries on the planet have their rivers, and most of them are now polluted. In the United States alone, the EPA’s National Rivers and Streams Assessment (2018–19) rated 47% of river and stream miles in poor biological condition, based on the health of their bottom-dwelling invertebrate communities — nitrogen and phosphorus pollution and degraded streamside habitat are the most widespread causes.
The following are some of the Most Polluted Rivers in the United States:
1. Calcasieu River
It is a river on the Gulf Coast in southwestern Louisiana. It is approximately 200 miles long. It runs through one of the densest concentrations of petrochemical plants and oil refineries in the United States. The EPA began investigating the Calcasieu Estuary in 1999 and found high levels of metals and hazardous chemicals in its sediments; in 2011 the agency reached a cleanup agreement with Phillips 66 and Sasol North America covering a two-mile stretch of Bayou Verdine, where contaminated sediment was dredged, sealed into a containment cell and capped.
Petroleum chemicals are being present in the waters poisoning the fishes, crabs, and other inhabitants. Recently chemical companies and oil refineries have agreed to pay the federal government for the contamination of this river.
Until today there are still health warnings in consuming fisheries from most of this river because these fishes are contaminated due to these illegal dumps of poisonous petroleum chemicals and other toxic chemicals, which makes this river one of the most polluted rivers in America.
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2. Ohio River
It is a river located at the Midwestern and Southern United States boundary, and it flows from Pennsylvania up to Illinois. It is approximately 981 Miles. The Ohio River supports about 160 species of fish and drains a basin of more than 25 million people, which is exactly why what enters it matters so much.
It also supports dozens of native freshwater mussel species, several types of turtles, six types of frogs, and four types of salamander.
The Ohio’s pollution comes from coal-fired power plants, steel and aluminium mills, and petrochemical works discharging along its length, plus nutrient runoff from farmland across the basin.
This is the most polluted river in the United States by discharge volume, and its size does not neutralise that. Industry released about 41 million pounds of toxic chemicals into the Ohio River Basin in 2020 — more than any other watershed in the country — and the Ohio also receives the largest volume of cancer-causing chemical discharges of any American river. Fish-consumption advisories are in force along much of its course, so it is not a uniformly safe habitat. American Rivers has also named the Ohio one of America’s Most Endangered Rivers.
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3. Mississippi River
The Mississippi River is the second-longest river in the U.S. It flows approximately 2,340 Miles from northern Minnesota up to the Gulf of Mexico. The Mississippi supports at least 260 species of fish — about a quarter of every fish species in North America — along with dozens of native mussel species, paddlefish and two kinds of sturgeon.
Unfortunately, since the Mississippi River flows through a total of 10 states, this river became polluted. The leading causes of pollution in this river are caused by sewage, city waste, and agricultural wastes like arsenic.
Imagine ten states dumping different kinds of wastes in just one river, which causes poisoning and a muddy brown color to the river’s waters.
The brown colour itself is mostly suspended sediment rather than a pollutant — the Mississippi has always carried a heavy silt load. The genuine problem is invisible: nitrogen and phosphorus from farm fertiliser drain down the basin and feed the Gulf of Mexico dead zone, a low-oxygen area that NOAA measured at 4,402 square miles in summer 2025 against a five-year average of 4,755 square miles, and in which most fish and shellfish cannot survive. That downstream consequence, not the water’s colour, is why the Mississippi ranks among the most polluted rivers in America.
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4. Holston River
It is approximately 136 Miles that flows from Kingsport, Tennessee, to Knoxville, Tennessee. It supports native freshwater mussels and a well-known tailwater trout fishery, and is a source of hydroelectric power for the state.
Even just passing through only one state, this river is still endangered and polluted.
The main culprit of pollution in this river is the Holston Army Ammunition Plant at Kingsport, the sole U.S. manufacturer of the military explosives RDX and HMX. Both compounds, and their manufacturing by-products, have been detected in the river downstream of the plant’s outfalls; RDX is classified by the EPA as a possible human carcinogen. These kinds of chemicals are very poisonous, not just for animals but also for human health.
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5. Harpeth River
Is approximately 125 Miles, and is located in Tennessee, Rutherford County. It is one of the most biologically diverse rivers in Middle Tennessee, supporting native freshwater mussels, smallmouth bass and a State Scenic River designation along part of its length.
This river also serves as a home to 4 types of turtles, five kinds of frogs, 32 different kinds of birds, and seven species of salamanders.
The Harpeth’s real problem is nutrient pollution, not smelting. The City of Franklin’s wastewater treatment plant is the single largest discharge on the upper river, permitted for up to 12 million gallons a day, while the city also withdraws up to 20% of the river’s flow during dry spells. In late summer the treated effluent can make up a large share of what is actually flowing. The nitrogen and phosphorus feed algae blooms that strip oxygen out of the water at night, which is what kills fish here. Tennessee lists stretches of the Harpeth as impaired, and a legal settlement brought by the Harpeth Conservancy and the Southern Environmental Law Center now requires tighter discharge management and expanded monitoring.
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6. New River
Is approximately 320 Miles long and flows through the U.S. states of North Carolina, Virginia, and West Virginia. Despite its name it is one of the oldest rivers on the continent, and its gorge supports native mussels and around 40 fish species.
Having lowlands and terrains, this river is quite popular for outdoor activities like hiking and camping.
But this river is already getting polluted. The main cause of pollution here is the increase in population around the area, which led to municipal and industrial wastes discharged into the river, which causes a highly foul odor.
Some chemicals like arsenic and mercury are also present in the river. Arsenic is one of the main causes of cancer in humans, while mercury is very poisonous.
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7. Savannah River
Is located at the borders of South Carolina and Georgia. This river is a source of drinking water and fish for most people of Chatham County, GA. It supports striped bass, American shad and the federally endangered shortnose sturgeon.
The Savannah has repeatedly ranked among the highest U.S. rivers for reported toxic industrial discharge in Environment America’s analyses of EPA Toxics Release Inventory data. Georgia and South Carolina both maintain fish-consumption advisories along it for mercury, which accumulates up the food chain and is a developmental neurotoxin in children. Upstream sits the Savannah River Site, a former nuclear-weapons production complex where the U.S. Department of Energy is still managing legacy radioactive and chemical contamination. That combination — industrial discharge, mercury advisories and a weapons-complex legacy — is why it belongs on this list, and it is a more precise statement than any single percentage figure.
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8. Cuyahoga River
Is located in Northeast Ohio, which divides the city of Cleveland. Fish had all but vanished from the lower river by the mid-20th century; more than 60 species have since returned. Cleveland is known as a major manufacturing city that caused the industrial pollution to this river.
Oil and other flammable industrial waste floated on the water in such quantity that the river repeatedly caught fire. The first documented Cuyahoga fire was in 1868, not the 1930s, and at least 13 fires are on record — in 1868, 1883, 1887, 1912, 1922, 1936, 1941, 1948, 1952 and 1969 among them. The 1912 fire killed five people; the 1952 fire was the most destructive, causing about $1.3 million in damage.
The last fire, on 22 June 1969, was small and out within half an hour, but the coverage it drew helped build the political momentum behind the creation of the EPA in 1970 and the Clean Water Act of 1972. The Cuyahoga is now the standard example of how far a river can recover once discharge is regulated.
This river was once the most polluted in the U.S., but it now has improved after some renovation projects were launched to improve this river’s condition.
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9. Buffalo National River
Is located in northern Arkansas. It is a popular destination for camping, hiking, and fishing.
It supports about 60 fish species and is the first river in the United States to be designated a National River, in 1972. Its pollution problem had a single dominant source: C&H Hog Farms, a 6,500-head operation opened in 2012 on Big Creek, a major tributary. State studies afterwards recorded rising levels of E. coli that by 2018 breached Arkansas water-quality criteria.
That source is gone. In June 2019 Arkansas bought the operation out for $6.2 million and imposed a permanent moratorium on new industrial-scale hog farms anywhere in the Buffalo River watershed. Nutrient legacy in the soil means recovery is not instant, and the moratorium has faced repeated legislative challenges — but the Buffalo is the one river on this list whose largest pollution source was actually removed.
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10. Tennessee River
Is approximately 652 Miles and is located in Tennessee Valley. The Tennessee is one of the most biologically diverse river systems in North America, with more than 200 fish species and around 100 freshwater mussel species.
But the population of these freshwater inhabitants is diminishing because of pollution like industrial chemicals, raw sewage, micro-plastics, and agricultural runoff like fertilizers.
Also urban and household wastes like bottles, plastics, tissue papers are already contributing to making this river to be one of the dirtiest rivers in America and a significant source of water pollution.
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11. Willamette River
Is approximately 187 Miles long and lies mostly in northwestern Oregon. The river hosts some marine inhabitants like Chinook Salmon, Steelhead Trout, Lampreys, and Coho Salmon. But this river also shares its habitat with other marine life like Crayfish, Mollusks, and Worms.
But the water pollution is already killing this habitat resulting in dead fish and toxic algal blooms. Having these kinds of fish at this river means it’s a very important natural resource for food.
But the construction of several dams in this river destroyed most of the breeding grounds of these fishes. It is causing the migration and depletion in the population of these fishes. But the main cause of pollution in this river is sewage waste.
The lower ten miles of the Willamette through Portland carry PCBs, dioxins, PAHs, DDT and heavy metals in their sediments, left by a century of shipbuilding, wood treatment and manufacturing. The EPA added Portland Harbor to the Superfund National Priorities List in 2000 and issued its final cleanup plan — the Record of Decision — in 2017. That plan calls for removing roughly 3 million cubic yards of contaminated sediment and remediating about 4.4 miles of riverbank, at an estimated cost of $1.05 billion over about 30 years, with more than 100 responsible parties involved. The contamination poses the greatest risk to subsistence and tribal fishers who eat resident fish.
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12. Delaware River
Is 419 miles long and passes through four states — Delaware, New Jersey, New York and Pennsylvania — before entering the Atlantic. None of its signature fish are extinct. American shad and striped bass are both still present and still fished, and Atlantic sturgeon survives, though the Delaware population is in serious trouble: fewer than 250 spawning adults are thought to remain. Atlantic sturgeon was listed under the Endangered Species Act in 2012 and that listing was reaffirmed after a five-year review in 2022.
The core water-quality problem is low dissolved oxygen in the urban stretch between Philadelphia and Wilmington, where treated sewage and industrial discharge depress oxygen below what young sturgeon need to survive. In 2025 the EPA finalised stricter dissolved-oxygen standards for that reach — the first update in roughly 50 years — explicitly to support the reproduction and growth of sturgeon, striped bass and shad. Plastic waste and combined sewer overflows during heavy rain add to the load — and as we have argued elsewhere, recycling alone will not solve the plastic problem reaching rivers like this one.
This is one of the causes that’s why many marine inhabitants and fishes are seen swallowing these plastic wastes and resulting in dead fish.
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13. Thames River
This is the Thames River in Connecticut, not the English one. It is short — about 15 miles from Norwich down to Long Island Sound — and is really a tidal estuary rather than a freshwater river, which is why it supports blue crabs, striped bass and grass shrimp. Its shortness is exactly why it is vulnerable: there is very little dilution between what enters it and the Sound.
A very obvious sign of pollution in this river is its green color due to algal blooms; these algal blooms cause low oxygen in the water, affecting or even killing fishes, crabs, and other inhabitants. The pollution is caused by a mixture of city wastewater and septic water.
With the city having an old sewage system, during heavy rainfalls, the system overflows and pushes these contaminants straight onto the river resulting in contaminated drinking water. Another contributor to the water pollution of this river is a Pharmaceutical company which is located within the area.
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14. Rock River
Is approximately 299 Miles long and is located in Illinois and Wisconsin. The Rock supports smallmouth bass, walleye, channel catfish, bluegill and black crappie, along with native turtles and freshwater mussels.
But pollution like nitrogen, phosphorus, and sediment, mainly caused by construction sites and urban areas, has already destroyed most of the river’s ecosystem. Blue-green algae are already present in the river’s waters which causes oxygen depletion, which kills most of its inhabitants.
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15. Mobile River
Is located in southern Alabama and is 45 miles long. It drains the Mobile-Tensaw Delta, the second-largest river delta in the United States and one of the most species-rich freshwater systems in North America — crayfish, freshwater snails and an exceptional diversity of native mussels and turtles.
These snails are very important in the balance of the river’s ecosystem; snails eat algae and maintain the quality of water in the river; they also serve as a food source for fish. But due to pollution, these snails are starting to diminish. Sediment washing off construction sites clouds the water and smothers the gravel beds those snails and mussels need.
Chemicals that are contaminating the river are mainly nitrogen and mercury. These kinds of chemicals are very poisonous to these snails and other marine inhabitants. Agricultural runoffs are also contributing to the pollution of this river.
So, these are the 15 Most Polluted Rivers in the United States: Calcasieu River, Ohio River, Mississippi River, Holston River, Harpeth River, New River, Savannah River, Cuyahoga River, Buffalo National River, Tennessee River, Willamette River, Delaware River, Thames River, Rock River, and Mobile River.
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Final Thoughts
Common pollutants come from industrial wastes and toxic chemicals like arsenic, mercury, lead, oil, pesticides, uranium, phosphates. And nitrogen. Also, common pollutants come from urban wastes, like sewage waste, plastic waste, manure, and other household wastes like tissue paper, plastic bottles, etc.
All of these contribute to destroying the water’s ecosystems and destroying the natural habitat for different kinds of marine species. Polluted rivers can also become health hazards to humans by breeding ground for diseases from microorganisms present in the contaminated water.
Remember, these kinds of pollution in rivers affect our natural resources and biodiversity and impose dangers on our health.
Swimming in contaminated water, washing your hands in it or drinking it can cause mild to serious health issues. Contaminated water can transmit illnesses such as cholera, salmonellosis, cryptosporidiosis, giardiasis and hepatitis A. (Malaria is spread by mosquitoes that breed in standing water, not by drinking or swimming in polluted water.) We can also acquire skin diseases like dermatitis, rashes, and allergies.
River pollution is not a uniquely American problem. The Yangtze in China and the Ganges in India carry some of the heaviest pollution loads of any large rivers on earth — the Ganges is also the last stronghold of the endangered South Asian river dolphin — but the Mississippi is North American, and the fixes that work are the same everywhere: regulate what industry discharges, treat sewage properly, and keep fertiliser on the field instead of in the water.
As governments ease regulations to promote economic development, the list is expected to expand. Unless steps are taken to clean up the rivers and stop future pollution dispersion, the ecosystem will deteriorate in these river areas. The cleaning of these rivers is the responsibility of the government and everyone around the world.
Secondly, self-discipline and responsibility within ourselves in proper garbage or waste disposal is also important to prevent further pollution on our environment. Recycling wastes is also a good help. Reduction of usage of plastics will also lessen the pollution.
Pollution control also calls for community participation from different sectors of our society. Industries should have more strict regulations in their waste disposal, and the government should provide the proper equipment and facilities to collect wastes from homes and streets.
Also, through public awareness campaigns on certain campaigns that help protect the environment, we can prevent further river pollution.
There are numerous methods we may use to decrease pollution in our waterways.
In conclusion, the polluted rivers in the United States require more from us to preserve them from further deterioration. They are meaningless without their natural habitat and life-support systems, which we are slowly destroying every day. We should not wait until it’s too late to take action.
Hopefully, this article has helped you to gain knowledge on the most polluted rivers in the United States. So, keep your environment clean and be aware that what you throw in the river can end up in our drinking water.
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