Meghan Hodges
Despite the Clean Water Act being passed in 1972, promising to end the discharge of pollutants into America's waters by 1985, the country's waterways continue to be contaminated by toxic chemicals. More than half of the country's lakes and rivers are too polluted for swimming, fishing, or drinking, with states like Indiana and Florida ranking among the worst for water pollution. This issue extends to America's watersheds, which encompass 22 hydrologic regions defined by the flow of water. While the specific watersheds vary year to year, the Alaskan and Great Basin regions, which include metal mines, were identified as having the most TRI chemical releases in 2022. The Columbia River, which runs through Washington state, received the most cancer-causing toxic chemical discharges between 1990 and 1994. The Mississippi River, which runs through multiple states, is also heavily polluted, with Louisiana-based fertilizer plants contributing significantly to its contamination.
| Characteristics | Values |
|---|---|
| Number of Hydrologic Regions in the US | 22 |
| Hydrologic Regions with the Most TRI Chemical Releases in 2022 | Alaskan and Great Basin Regions |
| Hydrologic Region with the Most TRI Chemical Releases Per Square Mile in 2022 | Great Basin Region |
| River with the Most Toxic Chemical Discharges between 1990 and 1994 | Columbia River |
| River with the Second Most Toxic Chemical Discharges between 1990 and 1994 | Quinnipiac River |
| River with the Third Most Toxic Chemical Discharges between 1990 and 1994 | Genesee River |
| River with the Fourth Most Toxic Chemical Discharges between 1990 and 1994 | Mississippi River |
| River with the Fifth Most Toxic Chemical Discharges between 1990 and 1994 | Thames River |
| Most Polluted River in the US based on Toxic Releases from the Industrial Sector | Ohio River |
| River Threatened by High Levels of Nitrogen and Phosphate Pollution from Agricultural Runoff | Mississippi River |
| River Filled with Raw Sewage, Industrial Chemicals, and Garbage | New River |
| River with More Than 120 Sewer Systems Linking Toilets and Faucets from New York to Maryland | Susquehanna River |
| Most Polluted Watershed Regions in Terms of Toxic Chemical Discharges | Ohio River, Great Lakes, and Texas-Gulf |
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What You'll Learn
The Mississippi River
Agricultural practices are a leading cause of water pollution in the Mississippi River. The excessive use of fertilizers by farmers has led to nutrient loading and eutrophication. The Clean Water Act (CWA) was enacted in 1972 to address point-source pollution, but non-point source pollution, like that from agriculture, remains challenging to regulate. While the CWA has had some success stories, such as improving water quality in Lake Pontchartrain, Louisiana, the goal of making all U.S. waters "fishable and swimmable" by 1985 has not been met.
Sedimentation, the filling in of the river and its backwaters with silt and sand particles, is another significant issue for the Mississippi River. This process can destroy fish and wildlife habitats, cover spawning grounds, and transport pollutants like PCBs, heavy metals, and phosphorus. While sedimentation has helped bury some pollutants downstream from Lake Pepin, improving water quality, the Upper Mississippi River is particularly vulnerable due to its vast drainage area and the altered natural movement of sediment caused by the lock and dam system.
The pollutants in the Mississippi River contribute to a biological dead zone, or hypoxia, at the river mouth in the Gulf of Mexico. Excess nutrients from the river and seasonal stratification of waters in the Gulf result in very low oxygen levels in the water, impacting aquatic life.
While efforts have been made to reduce pollution, such as increased awareness and the implementation of laws like the Clean Water Act, the Mississippi River remains a highly polluted watershed, facing challenges from agricultural runoff, sedimentation, and toxic chemical contamination.
Legislation and Pollutants: What's the Current Regulatory Scope?
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The Columbia River
Efforts are being made to restore the health of the Columbia River. Releasing more water from the dams in the spring can help improve flows for salmon and other species, and combined with improved dam operations, floodplain and estuary restoration, and the construction of fish passages, the future for the river's ecosystem could be positive.
Trees: Natural Pollution Absorbers or Not?
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The Genesee River
The river's pollution is largely attributed to industrial activity, with companies such as Eastman Kodak, Cytec Industries, and Xerox cited as past major polluters. Between 1990 and 1994, Kodak dumped nearly 879,000 pounds of cancer-causing chemicals into the river, making it the largest polluter of carcinogenic chemicals in the nation during that period. While toxic pollution has decreased in recent years, the river still carries high levels of silt and sediment, as well as pesticides, which have led to health advisories warning against consuming fish from the lower part of the river.
The non-profit organization Genesee RiverWatch has been working to improve the river's health and reduce pollution from agriculture. They have been grading the river's water quality, and in 2019, it received a "C". Despite this, there has been an acknowledgment that the water quality of the Genesee River is better than it used to be, and efforts to develop the area around the river, considered the lifeblood of Rochester, are underway.
The river's fast-flowing nature helps to flush out bacteria, and the algae blooms that plague Lake Ontario are often swept away by the Genesee's current. While swimming in the river is not recommended, especially downstream of Rochester due to urban runoff and legacy toxic pollution, it is believed that the health risks are not as high as they once were.
Pollution vs Drought: Understanding the Key Differences
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The Ohio River
The river is also affected by nutrient pollution, with high levels of nitrogen and phosphorus contributing to toxic algae blooms. This pollution comes from both urban and rural sources, including runoff from farms, suburban and urban properties, and municipal sewers. The Ohio River Valley has a history of fossil fuel extraction, and many communities in the area continue to struggle with water pollution and other public health challenges.
Efforts are being made to clean up the river and protect its water quality. The Ohio River Valley Water Sanitation Commission (ORSANCO) was founded in 1948 by states throughout the watershed to establish multi-state environmental standards. Environmental organizations like the Environmental Law & Policy Center (ELPC) and the Ohio River Foundation (ORF) are working to ensure that polluting industries are held accountable and that science-based water quality standards are adopted and enforced.
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The Great Lakes
Despite their enormous importance, the Great Lakes have been degraded for over a century as industry and development expanded around them. By the 1960s, Lake Erie was predominantly polluted, largely due to the heavy industrial presence along its shores. The river in Detroit, for example, carried acids, iron and oil wastes into the lake. Runoffs from farms also carried wastes into the lake. Other rivers running into Lake Erie, including the Cuyahoga, were so polluted that they were catching fire. In 1965, Maclean's magazine described Lake Erie as "an odorous, slime-covered graveyard".
Lake Ontario was also heavily polluted by the 1960s. The lakes were used as waste disposal sites and became heavily polluted with chemicals, toxic pollutants, pesticides, and heavy metals. These toxins are capable of causing cancer, birth defects, and damage to the nervous and immune systems.
In 1978, the US and Canada updated the Great Lakes Water Quality Agreement to cover all five lakes and focus on chemicals and toxic substances. This agreement set common targets for controlling a variety of pollutants in Lake Erie, Lake Ontario, and the upper St. Lawrence River. While many hazardous sites have been slowly cleaned up, toxic pollution remains a problem.
Today, plastic pollution is a serious problem for the Great Lakes. More than 22 million pounds of plastic end up in the Great Lakes every year, breaking down into microplastics that are ingested by humans and wildlife.
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Frequently asked questions
The US Geological Survey divides the country into 22 hydrologic regions or watersheds. The Environmental Working Group estimates that the total load of toxic pollution in most rivers, streams, lakes, and bays may be 20 times greater than the amounts reported. More than 700 million pounds of toxic chemicals were dumped into the Mississippi River between 1990 and 1994, and it is considered one of the most polluted rivers in the US. Other polluted watersheds include the Pacific Ocean, the Ohio and Tennessee Rivers, the Houston Ship Channel, and Ward Cove in Alaska.
Water pollution is caused by a variety of factors, including industrial discharges, agricultural runoff, and sewage spills. In the case of the Mississippi River, 90% of the pollution came from three fertilizer plants in Louisiana.
Polluted watersheds pose significant risks to both human health and the environment. According to a 1998 study, water pollution was blamed for one-third of all reported gastroenteritis cases and two-thirds of ear infections. Untreated sewage in water can spread infectious diseases such as salmonella, hepatitis, dysentery, and cryptosporidium.
The Clean Water Act, passed in 1972, was a landmark legislative achievement aimed at ensuring "fishable, swimmable" water across the US. However, it has fallen short of its goals due to insufficient funding, weak enforcement, and a lack of control over agricultural runoff. Efforts to improve water quality include targeting major polluters, updating industry-specific technology-based limits for water pollution control systems, and improving sewage treatment processes.
