Water pollution in the United States has become a serious problem. It started to grow in the 19th century when industries like farming, mining, and manufacturing began to use machines. Laws created in the late 20th century helped improve water quality in many areas. However, heavy industrial activity and fast-growing cities made water pollution worse. Without strong rules, harmful things like sewage, chemicals, and nutrients were released into rivers, lakes, and other water sources. This has made it clear that more work is needed to protect water quality, as it is still not completely safe.
In the early 1900s, communities began building systems to treat drinking water. But until the 1970s, the main causes of pollution—such as household waste, factories, and farming—were not properly controlled. These pollution sources can harm both groundwater and surface water. Major pollution events, like the Kingston Fossil Plant coal spill in 2008 and the Deepwater Horizon oil spill in 2010, caused long-term damage to water quality, ecosystems, and people’s health. In 2023, the United States Geological Survey (USGS) found that at least 45% of drinking water in the U.S. contains per- and polyfluoroalkyl substances (PFAS), often called "forever chemicals." The Environmental Protection Agency (EPA) has identified about 70,000 water areas that do not meet updated water quality standards because of PFAS.
To reduce water pollution, solutions like treating wastewater from cities, farms, and industries, controlling erosion, and managing rainwater runoff can be used. Ongoing efforts to prevent, control, and treat pollution aim to keep water quality within limits set by federal and state laws. However, many water sources across the country still fail to meet these standards in the 21st century.
Overview
In the 19th century, scientists, government officials, and the public in the United States noted that water pollution was becoming a bigger problem. At that time, many cities and towns sent untreated waste from homes directly into nearby rivers, lakes, and streams. As the economy grew, factories, mines, and other businesses added more polluted water to these waterways. In the early 20th century, large cities and later smaller towns started building systems to clean drinking water, but sewage treatment systems were limited and not very effective. It was not until later in the century that efforts to control sewage and industrial pollution became more complete. In the 20th century, pollution from farms increased because of the use of machines and more chemicals in agriculture.
After the 1972 Clean Water Act (CWA) was passed, pollution levels in U.S. waterways dropped greatly, especially from sewage and many types of industrial waste. However, the 1972 law did not address pollution from farm runoff or runoff from cities. In 1987, federal rules were added to control stormwater runoff from cities and towns, but implementing these rules has been slow and difficult. In the 21st century, about half of U.S. streams and rivers still do not meet federal water quality standards. Surveys showed that about 70% of lakes, ponds, and reservoirs are impaired, and more than 70% of coastlines and 90% of ocean and near-coastal areas studied are also impaired. A 2017 report by the Environmental Protection Agency (EPA) found that 46% of river and stream miles, 21% of lakes, 18% of coastal and Great Lakes waters, and 32% of wetlands are in "poor biological condition." In the 21st century, many water bodies remain polluted due to waste from farms, certain industries, and urban runoff, which can harm the environment and human health.
Although the Clean Water Act has improved water quality in many areas, it does not fully address all pollution issues. Some people believe Congress should update or expand the law to fix these problems and gaps in rules. The CWA has been successful in controlling pollution from specific sources, such as pipes or ditches, where responsibility is clear. However, it has been less effective in controlling pollution from many different sources, which is harder to manage and may be costly to prevent.
Despite the harm caused by water pollution, solutions exist to reduce and treat pollution in water bodies.
Types
Surface water includes all visible water sources, such as oceans, lakes, and rivers. In the United States, many surface freshwater sources are polluted. This is a big problem because more than 60% of the water used in the United States comes from these sources. Most freshwater pollution happens because too much fertilizer and farm waste enter water bodies, which lowers oxygen levels in those areas.
Groundwater is rainwater that collects in underground spaces called aquifers. People can reach this water by drilling wells to bring it to the surface for use. About 40% of the drinking water in the United States comes from groundwater. When harmful substances enter aquifers, the pollution spreads, making the water unsafe to drink. Groundwater pollution often happens when chemicals like pesticides, fertilizers, gasoline, oil, road salt, septic tank waste, or leaked materials from landfills seep through the soil and into the water supply.
Categories of pollution sources
Point source pollution happens when water pollution comes from one specific place. Examples of point sources include broken septic tanks, oil spills, waste dumping, or wastewater treatment plants. To stop this type of pollution, the Clean Water Act sets rules about what can be released into water. It requires each facility to get a permit called a National Pollutant Discharge Elimination System (NPDES) before discharging anything into water.
Nonpoint source pollution happens when water pollution comes from many different places. This type of pollution is hard to control because the exact source may be unclear. It is the most common type of pollution because rainwater flowing over land can pick up pollutants from the environment along the way. These pollutants might come from farming, city streets, or drainage systems. The Clean Water Act does not allow permits like NPDES for nonpoint sources.
Trans-boundary water pollution occurs when pollution from one country moves into another country’s water or environment. This pollution can travel through rivers or ocean currents, meaning it is not limited to one nation. Because it uses natural waterways, this type of pollution can spread over long distances.
Causes of pollution
Historically, municipal sewage was a major cause of water pollution in the United States. Without proper treatment, sewage led to many polluted water bodies across the country. Domestic sewage became a widespread problem during the 19th century, as the population grew and more people moved to cities. In the early 20th century, most communities did not have sewage treatment plants or waste disposal systems. Some cities built sewer pipes to carry sewage to rivers or coastal areas, but they did not treat the waste before releasing it into water. The first wastewater treatment plants were built in the late 19th and early 20th centuries, but they often did not fully clean the waste.
After the 1972 Clean Water Act was passed, new and improved sewage treatment systems were built, which greatly reduced pollution from cities. Since the 1980s, secondary treatment has been the national standard for wastewater. Today, the United States processes about 34 billion gallons of wastewater each day. However, some systems still cause water quality issues because of old or broken pipes and collection systems, leading to leaks and overflows. Poor maintenance of sewer systems causes contamination, which led to a "D" grade for the nation’s wastewater infrastructure in 2017. While all domestic wastewater is treated now, leaks and spills still pose a problem because wastewater can carry diseases like salmonella, hepatitis, and others that make about 3.5 million Americans sick each year.
Research in the late 1970s and 1980s showed that stormwater runoff was a major cause of water pollution in many parts of the United States. Stormwater pollution continues to be a problem today. As land in cities and suburbs has developed, more impervious surfaces like roads, parking lots, and buildings have been created. These surfaces increase runoff during rain, which carries pollutants like gasoline, oil, metals, fertilizers, and chemicals into waterways.
Industrial waste pollution in the United States was first observed in the 1870s. As the Industrial Revolution and later the Second Industrial Revolution grew, more waste was produced and released into water. Industrial waste can harm ecosystems and human health if it enters water directly. Early industries like mining, iron forges, and blast furnaces produced waste that was often diluted but still harmful. As factories expanded in the 19th century, more pollution was created. The use of steam engines and railroads increased demand for coal and minerals, leading to more waste.
By the mid-19th century, industrial waste production increased in many sectors, including mining. Mining waste came not only from coal and mineral mines in the east and south but also from gold, silver, and metal mines in the west. The Second Industrial Revolution brought new industries like oil and gas extraction, petroleum refineries, iron and steel manufacturing, and chemical production. These industries created more waste, including toxic chemicals. Industrial growth continued into the 20th century, with paper manufacturing adding more waste.
Today, industrial pollution comes from factories that discharge wastewater into waterways. In 2015, the EPA found that coal-fired power plants were the largest source of industrial water pollution, releasing toxic chemicals like mercury, arsenic, and lead. While many facilities now treat their wastewater to meet regulations, some industries still release significant pollutants.
According to a 2019 report, industrial and commercial facilities in the United States released about 200 million pounds of toxic pollutants, a decrease from 2007. However, not all industries or pollutants are covered by these reports.
Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals used in modern manufacturing. They are hard to break down, which is why they are called "forever chemicals." People and animals are often exposed to PFAS through water and food. A 2023 study found that nearly half of tap water in the United States contains PFAS. Research is ongoing to understand the full health effects of PFAS, which may include higher cholesterol, weakened immune systems, increased cancer risk, and problems with reproduction and development.
Agricultural activities also contribute to water pollution. Rainwater carries fertilizers, animal manure, and chemicals from farms into water bodies. Nutrients like nitrogen and phosphorus from these sources can cause eutrophication, leading to algal blooms. These blooms use up oxygen in water, creating dead zones where aquatic life cannot survive. Overuse or misuse of fertilizers, pesticides, and other chemicals during farming worsens this problem.
Solutions
Municipal wastewater (sewage) is made up of human waste and other waste from homes. In the United States, about 34 billion gallons of wastewater are collected daily and sent to sewage treatment plants. Wastewater is collected through combined sewer systems, which handle both sanitary waste and stormwater, or through separate systems for sanitary waste only. Sewage treatment plants use physical methods, such as screens and settling tanks, and biological processes to remove organic matter and harmful germs from water. These plants must follow strict rules to ensure their wastewater does not harm the environment or public health. Some plants use advanced methods to reduce nutrient pollution before releasing treated water.
Agricultural runoff is a major source of water pollution in the United States. Farmers can use funding from Clean Water Grants to install projects that help control pollution before it reaches water sources. Ways to reduce agricultural pollution include managing watersheds, controlling nutrients, planting cover crops, creating buffers, managing livestock waste, and managing drainage. Buffers are small areas of plants that help remove pollutants like nitrogen, phosphorus, and sediment before water flows into bodies of water. Both buffers and cover crops are used to reduce these pollutants in runoff.
Industrial facilities may produce different types of wastewater:
– Manufacturing waste, which includes pollutants that can be controlled with basic treatment systems, harmful substances like solvents and heavy metals, and other harmful compounds such as nutrients
– Non-manufacturing waste, such as water from boilers and cooling systems, which can cause heat pollution and other issues
– Industrial site drainage from manufacturing, service industries, and energy and mining operations
– Wastewater from energy and mining activities, such as acid mine drainage, water from oil and gas extraction, and radioactive materials
– Wastewater from treatment or cooling processes, such as water used to clean filters or brine
Some industrial wastewater can be treated in municipal sewage plants. However, most industrial facilities, like petroleum refineries and chemical plants, have their own special systems to treat wastewater. These systems are designed to handle high levels of organic materials (like oil and grease), toxic substances (like heavy metals and chemicals), or nutrients like ammonia. Some industries use pre-treatment systems to remove certain pollutants before sending partially treated water into the municipal sewer system.
Erosion and sediment controls are methods used to reduce sediment pollution in waterways. On farms, crop management is a common and effective way to prevent erosion. Practices like planting cover crops, rotating crops, and leaving crop residue in fields help keep soil in place. Without proper soil protection, rain can wash large amounts of sediment into waterways, which can reduce sunlight and visibility. On construction sites, measures like erosion control mats, mulch, and silt fences are used to trap sediment.
Urban areas affect water quality by increasing runoff and pollution. One way to reduce runoff is to use pervious pavers, which allow rainwater to flow into groundwater and lower the amount of runoff. Proper storage and use of household chemicals are also important to prevent spills that can pollute local waterways.
Recent large-scale pollution incidents
The Deepwater Horizon oil spill is the largest marine oil spill in the history of the petroleum industry. The event began on April 20, 2010, when a BP oil rig exploded in the Gulf of Mexico about 41 miles from the coast of Louisiana. The explosion caused oil to leak at a rate of 1,000 to 60,000 barrels per day. It took 87 days for responders to stop the spill, which had released an estimated 3.19 million barrels of oil into the Gulf. Over 1,000 miles of shoreline along the Gulf of Mexico, from Texas to Florida, were affected by the spill.
Eleven crew members died, and 17 were seriously injured during the incident. Hurricanes in the Gulf can carry crude oil toward the shore, increasing the risk of long-term health effects. A study from LSU found that people exposed to crude oil over 10 years may face permanent damage, including higher cancer risks, heart problems, and breathing issues. Another study on Coast Guard workers who helped clean up the spill showed that 54.6% were exposed to crude oil, and 22.0% were exposed to oil dispersants. Of nearly 5,000 workers surveyed, 19.4% reported coughing, 5.5% had trouble breathing, and 3.6% experienced wheezing. Workers exposed to both oil and dispersants had stronger links to these symptoms than those exposed to oil alone.
The northeast Gulf of Mexico shoreline has about 60% of the U.S.’s coastal and freshwater marshes. Marshes often have standing water, making them very vulnerable to oil spills. Oil can coat plants for long periods, harming ecosystems that support many species. The Gulf is home to 22 marine mammal species. Up to 20% of Kemp’s ridley sea turtles and 50% of Louisiana Bottlenose dolphins affected by the spill died. However, because the spill occurred far from land, it caused less damage to coastal ecosystems than other spills. Tar balls still reached shorelines, harming wildlife. The effects of oil on deep-sea ecosystems remain unclear.
In December 2010, the U.S. filed a lawsuit against BP and others involved in the spill. A settlement required BP to pay $5.5 billion in penalties and up to $8.8 billion for environmental damage. By 2015, BP had recovered most of the $40 billion in lost value after the spill. The company expanded its oil operations in the Gulf and invested in projects in Alaska. However, a 2015 NPR article noted that Gulf Coast fishing communities still face challenges from the spill. An Alabama oysterman said, "Business is still struggling…because of the lack of oyster production…I place the blame for that on the oil spill."
Water pollution in Woburn, Massachusetts, became public in 1984 after families of children with leukemia sued the town. They blamed the town’s drinking water, which had been polluted for over 150 years by toxic chemicals from leather factories and food plants. These chemicals, trichloroethylene and perchloroethylene, are linked to cancer and leukemia.
The Martin County coal slurry spill happened on October 11, 2000, when 306 million gallons of slurry entered the Tug Fork River. The spill polluted 200–300 miles of the Big Sandy River and affected the water supply for over 27,000 people.
On December 22, 2008, a dike at the Kingston Fossil Plant in Tennessee broke, releasing 1.1 billion gallons of coal fly ash slurry into the Emory River. This was the largest coal ash disaster in U.S. history. Nearly 30 workers died, and over 100 were sick years later. Many other coal ash incidents have harmed rivers, lakes, and ecosystems.
On August 5, 2015, workers at the Gold King Mine in Colorado released 3 million gallons of toxic wastewater into a river. The water had unsafe levels of heavy metals, with some areas testing hundreds of times above limits.
On January 19, 2026, a sewer pipe collapsed, releasing over 300 million gallons of raw sewage into the Potomac River. DC Water used a bypass system to divert wastewater into a dry section of the Chesapeake and Ohio Canal. The bypass was improved with pumps and completed on March 14, 2026. DC Water then began long-term repairs to strengthen the pipe.
Regulations
During the late 1800s, the federal government did not pay much attention to environmental and health problems that were seen as local issues. Some states, like Massachusetts, New Jersey, Connecticut, and Rhode Island, studied pollution in certain rivers within their borders but did not create rules for the industries causing the pollution. The only federal law addressing water pollution during this time was the Rivers and Harbors Act of 1899. This law banned the dumping of "refuse," which included materials that blocked waterways, but it did not cover other types of pollution, such as sewage, food waste, chemical waste, or oil spills. In 1924, Congress passed the Oil Pollution Act to address oil spills in harbors. This law set penalties for oil spills, but only for ships in coastal waters.
In the early 1900s, the United States Public Health Service (PHS) began studying waterborne diseases and drinking water contamination. In 1914, the PHS published drinking water standards that applied only to railroads moving goods between states. The PHS could not create broad pollution rules, but it shared suggested standards for city water systems. These standards later influenced the Safe Drinking Water Act of the 1970s. In 1922, the American Water Works Association released a report identifying industries that caused pollution, such as mining, food processing, and chemical manufacturing. However, these industries were not studied in detail at the time, and most public health workers focused on pollution from untreated sewage.
In the 1920s, water scientists agreed that pollution from acid mine drainage and coke manufacturing (which produces harmful chemicals called phenols) was a major problem. In 1924, a voluntary agreement was made between the U.S. Surgeon General, state agencies, and manufacturers in the Ohio River valley to reduce phenol pollution from coke plants. However, the PHS reported that acid from mining had a germ-killing effect and did not recommend controlling this pollution. The PHS also studied pollution in major rivers and the Great Lakes. These studies helped create the Streeter–Phelps equation, a tool used to predict how pollution affects oxygen levels in water.
Starting in 1917, some states formed water commissions or boards to monitor water quality and share findings with health agencies. These groups studied pollution but did not create rules, relying instead on industry cooperation.
In 1948, Congress passed the Federal Water Pollution Control Act, which created a wide range of water quality programs and provided funding for states and local governments. Enforcement was limited to waters that crossed state lines. The PHS offered financial and technical support.
The Clean Water Act is the main federal law in the U.S. that controls water pollution in rivers, lakes, and other surface waters. The 1972 amendments to the law created a system for controlling pollution and setting standards for water quality. The law allows the Environmental Protection Agency (EPA) to regulate surface water pollution, working with state agencies. Before 1972, it was legal to release wastewater into surface waters without testing for or removing pollutants. The Clean Water Act was updated in 1981 and 1987 to adjust funding for local governments, regulate stormwater from cities, and create the Clean Water State Revolving Fund. This fund provides low-cost loans to improve sewage treatment systems and other water quality projects.
Under the Clean Water Act, the National Pollution Discharge Elimination System (NPDES) requires permits for wastewater discharges into water bodies. Facilities must apply for permits and treat their wastewater. Permits also include rules for monitoring and reporting pollution, which help the EPA and states enforce limits. However, more than half of U.S. rivers still fail to meet state pollution standards. Some states have stricter rules for protected water areas, and additional rules may target pollution from farming and other nonpoint sources. The EPA and states use a tool called Total Maximum Daily Load (TMDL) to set strict pollution limits for both point sources (like factories) and nonpoint sources. In 2010, the EPA and states created detailed TMDL rules for the Chesapeake Bay. State agencies are now developing similar rules for other water bodies across the U.S.
Some economists questioned whether the 1972 law achieved its goal of cleaner water and whether the benefits outweighed the costs. The U.S. government has spent over one trillion dollars to reduce water pollution. The law aimed to make all water clean by 1983, but this goal was not met. Overall, water quality has improved since 1972, but not all pollution has been removed. Between 1972 and 2001, the number of waterways safe for fishing increased by 12 percent. However, data on this improvement is limited, as only 19 percent of U.S. waterways had been tested for contamination.
Groundwater protection is covered by the Safe Drinking Water Act, the Resource Conservation and Recovery Act, and the Superfund Act.