most polluted bodies of water

The 7 Most Polluted Bodies of Water in the US 

Steve Russell - November 2, 2022

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Do you know that one reason it’s so challenging to measure the impact of climate change is that it consists of various facets? Ozone depletion is only part of the picture. The nation’s waterways also take a hit. 

Where should you exercise caution before swimming or release anything you catch, lest you dine on contaminated food? Here are the seven most polluted bodies of water in the U.S. Do you live near any of them? 

1. The Mississippi River 

A lot has changed since Mark Twain envisioned Huckleberry Finn floating peacefully down the Mississippi. This once pristine waterway is perhaps the most polluted in the United States. 

Part of the problem stems from agriculture. The Mississippi River traverses much of America’s heartland, drawing no end of runoff from factory farms. Animal waste isn’t the only problem. Chemical fertilizers spill into waterways and pollute nearby groundwater supplies, damaging native wildlife and rendering water unsafe for use. 

A major curse of agricultural runoff is eutrophication. This term refers to how fertilizers like nitrogen and phosphorus increase the nutrient content of water, spurring algae growth. This coating on the water’s surface asphyxiates what lies below the surface, killing native flora and fauna and potentially causing entire species to go extinct. 

2. The Ohio River 

Steel is one of the commodities that helped America reach economic superiority in the early part of the century. Many plants still exist along the Ohio River, and the runoff from these facilities renders this waterway one of the ten most polluted in the United States. 

The toxins found here consist primarily of nitrate compounds. These chemicals are notoriously difficult to remove once they enter waterways. Mercury makes up another common pollutant, making the surrounding area hazardous for little ones who like to put everything in their mouths. 

3. The Pacific Ocean 

For far too many years, people disposed of waste by dumping it into the ocean. However, much of the trash thrown there never disintegrates, at least not for many lifetimes. Approximately 90% of the visible rubbish seen in the Pacific waters consists of plastic. What’s even worse is that this substance never fully biodegrades, breaking down into microplastics that poison marine life. 


Recreational activity also supplies some waste as residents and tourists flood beaches in the summer, often leaving trash behind. Another problem is nuclear waste. Leaks like the Fukushima one contaminate waters. Additionally, the liquid pulls contaminants from the air, adding to the radioactive mess. 

4. The Atlantic Ocean 

If you’ve ever gone down to the Jersey shore, the waters off the coast probably appeared more gray-brown than blue. That’s because of the high levels of industrial and agricultural runoff that continue to pollute this body of water. 

Unfortunately, the reality of climate change makes mighty bodies of water like the Atlantic even harder to clean. More frequent and severe hurricanes lead to agricultural runoff entering the ocean, as in Hurricane Florence when it struck in 2018. The area off the North Carolina coast is home to roughly 2,400 hog farms, all of which produce cesspools of wastes that flow into the ocean and other waterways when floodwaters rise. 

5. New River 

The U.S.-Mexico border sees no end of trouble, and the problems don’t begin and end with immigration woes. Even migrants seeking a better life often emerge from traversing this waterway covered in itchy sores and rashes. If so much as a single splash crosses their lips, they can become violently ill, a severe problem in a climate where water is hard to find. 

Many people who live in the surrounding area have become sick with cancer. Much of the pollution stems from factories in Mexicali. 

6. The Savannah River 

The Savannah River ranks third in the country for toxic discharges. Industrial facilities dumped over 10 million tons of contaminants into this waterway in 2012 alone. 

Much of the problem stems from court cases brought by polluters that stripped many area waterways of protections ensured by the Clean Water Act. The Environment Georgia Research and Policy Center, its allies and the Environmental Protection Agency have proposed closing a loophole and restoring safeguards, but repairing the damage will take considerable time. 

7. Onondaga Lake 

Once upon a time in the 19th century, Onondaga Lake was a popular tourist destination, replete with beaches, resorts and amusement parks. However, industrial pollution combined with agricultural runoff and wastewater rendered the lake unsafe for swimming by 1940 and fishing by 1970. Today, you won’t find any colorful umbrellas lining its shores. 

Recent revitalization efforts have made the lake cleaner than in 100 years. It reopened to fishing in 1986. It was designated as a superfund site in 1994. 

The Most Polluted Bodies of Water in the US

“Don’t drink the water” should only apply to biological organisms, not human-made pollutants. However, contamination levels in America’s waterways have rendered many unsafe for drinking or bathing — mere contact can cause skin problems in some cases. The seven listings above may be the most polluted bodies of water in the U.S., but it is everyone’s responsibility to safeguard nearby shorelines and do what they can to help in cleanup efforts. 


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About the author

Steve Russell

Steve is the Managing Editor of Environment.co and regularly contributes articles related to wildlife, biodiversity, and recycling. His passions include wildlife photography and bird watching.