Water pollution in the United States

Water pollution in the United States is a growing problem that became critical in the 19th century with the development of mechanized agriculture, mining, and industry, although laws and regulations introduced in the late 20th century have improved water quality in many water bodies.[1] Extensive industrialization and rapid urban growth exacerbated water pollution as a lack of regulation allowed for discharges of sewage, toxic chemicals, nutrients and other pollutants into surface water.[2][3]

Topsoil runoff from farm, central Iowa, USA (2011).

In the early 20th century, communities began to install drinking water treatment systems, but control of the principal pollution sources—domestic sewage, industry, and agriculture—was not effectively addressed in the US until the later 20th century. These pollution sources can affect both groundwater and surface water. Multiple pollution incidents such as the Kingston Fossil Plant coal fly ash slurry spill (2008) and the Deepwater Horizon oil spill (2010) have left lasting impacts on water quality, ecosystems, and public health in the United States.[4][5]

Many solutions to water pollution in the United States can be implemented to curtail water pollution. This includes municipal wastewater treatment, agricultural and industrial wastewater treatment, erosion and sediment control, and the control of urban runoff. The continued implementation of pollution prevention, control and treatment measures are used to pursue the goal of maintaining water quality within levels specified in federal and state regulations. However, many water bodies across the country continue to violate water quality standards in the 21st century.[6]

Overview
Dead zone in the Gulf of Mexico.

Water pollution was identified as a growing problem in the US by scientists, government officials and the public in the 19th century. Many cities and towns piped their untreated domestic sewage into nearby waterways. Wastewater discharged by factories, mines and other businesses increased as the economy expanded. Large cities, and later smaller communities, began to install drinking water treatment systems in the early 20th century,[7] but sewage treatment plants were limited at that time and not very effective.[2] Effective control of sewage and industrial pollution was not comprehensively addressed until later in the century. Agricultural pollution emerged as a growing problem in the 20th century with the increased mechanization of agriculture[8] and increasing use of chemicals.[9]

Following the passage of the 1972 Clean Water Act (CWA), the levels of water pollution in US waterways generally have experienced a dramatic decrease with respect to sewage treatment and many types of industrial wastewater.[1] However, more than half of U.S. stream and river miles continue to violate federal water quality standards in the 21st century. Surveys of lakes, ponds and reservoirs indicated that about 70 percent were impaired (measured on a surface area basis), and a little more than 70 percent of the nation’s coastlines, and 90 percent of the surveyed ocean and near coastal areas were also impaired.[6]

Agriculture, industry, urban runoff, and other sources continue to discharge waste into surface waters nationwide. This poses huge environmental and health risks given that these water sources are used as drinking water and for agricultural use.

While the CWA has made positive contributions to the state of surface water in the United States, the law does not fully address all aspects of pollution. Many think that Congress should revise or expand the law to address these problems and gaps in regulation.[10] Although the CWA has been effective in controlling point source pollution (where the discharge is typically via a pipe or ditch and assigning responsibility for mitigation is straightforward), it has not been as effective with nonpoint sources (where discharges are diffuse, and treatment or prevention may be technically difficult or very expensive).[11]

Despite the negative health and ecosystem impacts of water pollution, solutions exist that are able to treat and decrease pollution levels in water bodies.

Types

Surface water pollution

Surface water consists of all forms of visible water sources, such as oceans, lakes, and rivers. Currently, a significant percentage of surface freshwater sources are polluted in the United States. This poses a huge threat to American water sources because over 60% of water used in the United States is from these freshwater sources. A majority of freshwater contamination cases are a result of nutrient pollution, which is the result of farm waste and fertilizer entering the water source and resulting in toxic zones with depleted oxygen levels.[12]

Groundwater pollution

Groundwater is rainfall that collects in porous spaces deep underground, which are called aquifers.[12] Humans can access the water that collects in an aquifer by building wells to pump the water to the surface for use. About 40% of drinking water in America comes from groundwater sources.[12] When contaminants enter aquifers, the pollution spreads, eliminating the potential to use the aquifer for drinking water. Groundwater contamination is often the result of chemicals that seep through the soil and into the water supply, such as pesticides and fertilizers. Other causes of contamination in groundwater includes gasoline, oil, road salts, septic tank waste, or leakage from landfills.[13]

Categories of pollution sources
Water pollution point sources

Point source

Point source pollution occurs when water pollution contamination comes from a single source. Point sources could include leaking septic tanks, oil spills, dumping of waste, or wastewater treatment facilities.[12] In order to prevent point source pollution from occurring, the Clean Water Act regulates what can be discharged into a water body by requiring each facility to obtain a National Pollutant Discharge Elimination System (NPDES) permit.[14]

Nonpoint source

Nonpoint source pollution occurs when the contamination derives from multiple different sources. This type of pollution is very challenging to manage given that the original source(s) may be difficult to identify.[12] Nonpoint source pollution is the most common type of pollution because as rainfall runs off of land on its path to different water sources, it becomes contaminated by pollutants from the surrounding area. These sources include agriculture related pollutants, urban runoff, or drainage. The CWA does not authorize the issuance of NPDES permits for nonpoint sources,[15]

Trans-boundary sources

Trans-boundary water pollution occurs when pollution in one country’s waters spreads and damages another country’s environment or water supply. Trans-boundary pollution can travel through rivers or ocean currents.[16]

Causes of pollution

Municipal sewage
The Hyperion Water Reclamation Plant serves the Los Angeles metropolitan area

Historically, municipal sewage was a major contributor of water pollution across the United States. The lack of proper treatment of sewage resulted in many contaminated water bodies across the county. Domestic sewage became a widespread problem with the onset of the industrial revolution in the 19th century, population growth and increasing urbanization. Through the early 20th century, most communities had no sewage treatment plants or waste disposal sites. Some cities built sewer pipes which carried their sewage to a nearby river or coastal area, but lacked any treatment of the wastes, instead depositing the sewage directly into the water.[2]:48–50 The first wastewater treatment plants were built in the late 19th and early 20th centuries in the United States and typically did not fully treat the wastes.[17]

The extensive construction of new and upgraded sewage treatment systems following the passage of the 1972 Clean Water Act has greatly reduced municipal discharges. Since the 1980s secondary treatment has been the national standard for municipalities.[18] Some individual systems continue to cause localized water quality problems due to outdated or leaking piping and collection systems, leading to combined sewer overflows and sanitary sewer overflows.[2]:56–57 Poor upkeep of sewer infrastructure results in contamination from leaks, and contributed to a rating from the American Society of Civil Engineers of a "D" grade for America's wastewater infrastructure.[19] While all domestic wastewater is now treated nationwide, leaks and spills of municipal sewage pose a significant problem because wastewater carries diseases like salmonella, hepatitis, and many other infectious diseases that roughly sickens about 3.5 million Americans every year.[20]

Urban runoff
Parking lots, roads and buildings are major sources of urban runoff

Water research during the late 1970s and 1980s indicated that stormwater runoff was a significant cause of water quality impairment in many parts of the US.[21] Increased land development throughout the country—in both cities and suburbs—has led to an increase in impervious surfaces (parking lots, roads, buildings, compacted soil), which generates increased surface runoff during wet weather.

The development of new roads and smooth surfaces have contributed to polluted waters easily flowing into nearby rivers, lakes, and the oceans across the USA.[22] These paved surfaces and roads restrict water from soaking into the ground, and instead allows water to freely flow across pavements while picking up chemicals, fertilizers, pesticides, and many other pollutants that causes water pollution in the bodies of water in the USA.[23]

Industrial pollution

Early indications of pollution from industrial waste in the United States existed since the 1870s, increasing as the industrial revolution expanded throughout the United States and its environmental impacts were observed more frequently.[24][25] Industrial wastes contribute toxic pollutants and chemicals and can have detrimental ecosystem and public health impacts if discharged directly into surface water.[25]

Growth of industrialization and industrial waste
Discharge from a paper mill in Jay, Maine in 1973

Historical accounts of early industrial activity in the US provide a general description of the kinds of waste generated. Mining operations (coal, metals, minerals), iron forges and blast furnaces were some of the early industries in the U.S. that generated waste. In the late 18th and early 19th centuries, wastes from mining operations entered rivers and streams, and iron bloomeries and furnaces used water for cooling.[26]:27, 32–33, 53 These industries were relatively small businesses generating small amounts of product,[27] and the wastes they discharged to rivers and streams were proportionately dilute. However as factories grew in the 19th century, so did the quantity of pollution produced. In the early 19th century, the introduction of steam engines in both the mining and manufacturing sectors (such as textiles) greatly expanded productivity, and increased use of the engines generated larger volumes of heated water (thermal pollution).[26]:52–53 The productivity gains, along with the introduction of railroads in the 1830s and 1840s—which increased the overall demand for coal and minerals—led to additional generation of wastes.[28][3]:68–69

The volumes and concentrations of industrial wastes increased significantly in the mid-19th century in multiple business sectors, including mining. Mining wastes were increasing, not only from coal and mineral mines in the east and south, but from mining of gold, silver and other metals in the newly-developing west.[3]:92–95 [29]

The onset of the second industrial revolution in the mid-to-late 19th century introduced new heavy industries in the US, generating larger volumes and new kinds of wastes. These industries included:

Industrial expansion continued into the 20th century, including large-scale expansion of paper products manufacturing, which produced additional types and quantities of wastes.[31][32]

Modern day industrial waste

Today, industrial pollution is caused by discharges and emissions from manufacturing plants, which continues to pollute surface waters nationwide.[33] Many manufacturing processes generate wastewater, contributing to the water pollution found in rivers, lakes, and oceans.[34] In 2015 the U.S. Environmental Protection Agency (EPA) found that fossil-fuel power stations, particularly coal-fired plants were the largest contributors of industrial water pollution.[35] EPA found instances where power plants dumped toxic pollutants, such as mercury, arsenic, and lead into surface waters.[4][36] The continuation of chemical dumping by industrial facilities plays a key role in water pollution today in the USA. According to the EPA, water pollution from industrial facilities is responsible for polluting water quality in more than 10,000 miles of rivers and more than 200,000 acres of lakes, ponds and estuaries nationwide.[37]

Agricultural pollution

Discharges and chemicals from agriculture greatly contributes to water pollution in the US, as rainwater flows through fields and into bodies of water.[38] The application of chemical fertilizers, collection of animal manure, and use of chemicals used by farmers results in nitrogen and phosphorus. When washed away from farming fields, nitrogen and phosphorus found in fertilizers can cause eutrophication of water bodies.[39] Eutrophication results in algal blooms which deplete oxygen in bodies of water, resulting in dead zones where life can no longer be sustained. Excessive use or improper use of fertilizers, pesticides, and various types of chemicals during farming contribute to water pollution, and are currently the third largest source for water pollution in lakes, second largest source of water pollution in wetlands, and a major contributor to pollution in estuaries and ground water.[40]

Other causes

Other activities that contribute to water pollution include:

  • Accidental leaks and spills from chemical handling, such as petroleum
  • Household disposal of products and chemicals that enter nearby water bodies
  • Spills of oil used for transportation.[41]

Solutions

Municipal wastewater treatment

Municipal wastewater (sewage) is composed of human waste and other residential waste streams.[42] In the United States, approximately 34 billion gallons of wastewater are collected every day and sent to sewage treatment plants.[43] Wastewater is collected through combined sewers, which are used for sanitary waste and stormwater runoff, or in separate sanitary sewers.[20] Sewage treatment plants include physical removal processes, such as screens and settling tanks, and biological processes to remove organic matter and pathogens from water.[44] Treatment plants have strict permit requirements to ensure that their discharges will not cause harm to the environment or public health.[18][45] Some plants have enhanced treatment processes to control nutrient pollution before discharge.[46]

Agricultural wastewater treatment
Main article: agricultural wastewater treatment

Agricultural run-off is one of the leading causes of water pollution in the United States.[12] Funding from Clean Water Grants are available to farmers to install projects to help control agricultural pollution before it enters water sources.[47] Methods to minimize and contain water pollution from agriculture in the United States include watershed efforts, nutrient management, cover crops, buffers, management of livestock waste, and drainage management.[39] Buffers are small strips of land covered in plants that are able to remove pollutants such as nitrogen, phosphorus, and sediment prior to discharge in a water body. Both buffers and crop covers are used to remove these pollutants from agricultural runoff.[48]

Silt Fence used for sediment control.

Erosion and sediment control

Erosion and sediment controls are techniques used to mitigate sediment pollution in waterways.[49] The most common and efficient control method on agricultural land is crop management, which increases soil cover and stabilizes slopes.[49] Without proper soil stabilization techniques, rainfall can cause large quantities of sediment to be washed away into waterways, creating issues with sunlight penetration and visibility. Typical preventive measures for construction sites include erosion control matting and mulching, and installation of silt fences to trap sediment not captured by the erosion controls.[50][51]

Control of urban run-off

Urban areas affect water quality by increasing the volume of run-off and pollutant loads. One solution to decrease run-off is constructing new surfaces with pervious pavers, that allow rainwater to pass through the surface to groundwater aquifers and decrease the quantity of urban run-off. Additionally, proper use and storage of household chemicals are critical to decrease incidences of spills that pollute local waterways.[52]

Recent large-scale pollution incidents

Deepwater Horizon oil spill
Oil from the Deepwater Horizon oil spill approaches the coast of Mobile, Alabama, 6 May 2010

The Deepwater Horizon Oil Spill is considered to be the largest marine oil spill in the history of the petroleum industry. The incident began on April 20, 2010 when a semi-submersible BP oil rig exploded in the Gulf of Mexico about 41 miles off of the coast of Louisiana.[53] The explosion led to discharges between 1,000 to 60,000 barrels of oil per day.[5] It took responders 87 days to stop the spill, at which point the rig had leaked an estimated 3.19 million barrels of oil into the Gulf. Over 1,000 miles of shoreline on the Gulf of Mexico, from Texas to Florida, were impacted by the Deepwater Horizon spill.[54]

Human health impacts

Of the crew members present during the Deepwater Horizon Oil Spill, 11 died and 17 were seriously injured.[55] In addition, the frequency of hurricanes in the Gulf makes the effects of long-term exposure on humans more applicable, as these storms are capable of carrying crude oil over miles of ocean towards the shore. According to a research article from LSU, “damages to those living in the presence of crude oil the past 10 years are likely permanent, as chronic exposure leads to increased cancer risks, cardiovascular issues, and respiratory problems.” Oil exposure and its respiratory effects were also analyzed in a study on the Coast Guard personnel deployed to help clean up the spill. The article has 54.6% of responders stating they were exposed to crude oil, and 22.0% stating they were exposed to oil dispersants. Of the nearly 5,000 personnel who completed the survey, 19.4% experienced coughing, 5.5% experienced shortness of breath, and 3.6% experienced wheezing. The study also found that exposure to both oil and oil dispersants presented associations that were much stronger than oil alone for the different respiratory symptoms.[56]

Environmental impacts

The northeast Gulf of Mexico shoreline contains about 60 percent of the coastal and freshwater marshes in the United States.[57] A marsh environment tends to have standing water, making it among the most sensitive habitats to oil spills. Without the natural cleaning mechanism that flowing water provides, oil is able to coat marsh vegetation for longer periods of time, ruining nurseries that then impact a host of interconnected species.[58] The Gulf of Mexico is also home to 22 species of marine mammals. Of these, up to 20 percent of all Kemp’s Ridley sea turtles present during the spill ended up dying, and the Louisiana Bottlenose dolphin ended up facing a 50 percent decline in population.[59] However, because the BP oil spill occurred miles from any land, it wasn’t as damaging to ecosystems along the shore as other oil spills. However, habitats along the shore were still exposed through balls of tar that would clump together and wash up on beaches, impacting local wildlife. Also, the consequences that drifting plumes of oil had on the deep-sea ecosystem is relatively unknown.[60]

Economic impacts

In December 2010, the U.S. filed a complaint in District Court against BP and several other defendants associated with the spill. The complaint resulted in a record-setting settlement, enforcing a $5.5 billion Clean Water Act penalty on BP Exploration & Production and up to $8.8 billion in natural resource damages.[61] However, by 2015, BP had successfully recuperated most of the $40 billion lost in market value after the spill. This recovery was attributed to the company’s inclination to continue exploring new oil resources despite the accident. Between 2011 and 2013, BP’s Gulf of Mexico oil rigs doubled, and they began investing $1 billion towards opportunities in Alaska in 2015.[62] On the other hand, a 2015 article from NPR exhibited how fishing cities along the Gulf Coast are still feeling harmful effects of the oil spill. In an interview with an oysterman from Alabama, he states, “business is still struggling...because of the lack of oyster production...I place the blame for that on the oil spill.” The fisherman goes on to describe how the oyster reefs off of Louisiana have not been producing like they should since the spill.[63]

Woburn, Massachusetts source water pollution

Water pollution in the city of Woburn, Massachusetts gained public recognition in the 1984 lawsuit filed by the families of children in Woburn who had died from leukemia in unusually high numbers.[64] The families attributed the leukemia to the town’s polluted drinking water which had been contaminated over 150 years of industry, most notably the toxic compounds used by leather factories in the area.[64]

Martin County coal slurry spill

The Martin County coal slurry spill occurred on October 11, 2000, when a coal slurry broke into an abandoned mine and sent an estimated 306 million gallons of slurry into the Tug Fork River. The spill polluted 200–300 miles of the Big Sandy River and a water supply for over 27,000 residents.

Kingston Fossil Plant coal ash spill

On December 22, 2008, a dike ruptured on the Kingston Fossil Plant in Roane County, Tennessee and released 1.1 billion gallons of coal fly ash slurry into the Emory River. It was the largest fly ash release and worst coal ash-related disaster in U.S. history.[4]

2015 Gold King Mine spill
Emergency tailing ponds constructed in response to the 2015 Gold King Mine Spill, pictured on August 7

On August 5, 2015 workers on the Gold King Mine in Silverton, Colorado released 3 million gallons of toxic wastewater when attempting to add a tap to the tailing pond for the mine. The wastewater carried unsafe levels of heavy metals, with some parts of the river testing for hundreds of times over their limits.[65]

Regulations

Historical

During the late 19th century, there was little federal government attention paid to what were considered to be local environmental and health problems. The only federal legislation to address water pollution during this era was the Rivers and Harbors Act of 1899.[66] In the 1899 law, Congress prohibited the dumping of "refuse"—debris that interfered with navigation—but other forms of pollution (e.g. sewage, food waste, chemical waste, oil spills) were not addressed.[67] In 1924, to address oil spills in harbors, Congress passed the Oil Pollution Act. The law provided for penalties in the event of oil spills, but they were applicable only to vessels in coastal waters.[68] In the 1930s and 40s, state water boards were created to monitor some aspects of water quality.

Current

The Clean Water Act of 1972 (CWA) was the first act of its kind to establish a broad regulatory framework for improving water quality in the United States. The CWA defines procedures for pollution control and developing criteria and standards for pollutants in surface water.[69] The law authorizes the Environmental Protection Agency to regulate surface water pollution in the United States, in partnership with state agencies. Prior to 1972 it was legal to discharge wastewater to surface waters without testing for or removing water pollutants. The CWA was amended in 1981 and 1987 to address municipal water treatment construction, regulate municipal storm sewer discharges and to later establish the Clean Water State Revolving Fund, which provides grants to states to improve municipal sewage treatment systems and finance other water quality improvements.[70]

Under the CWA, the National Pollution Discharge Elimination System (NPDES) regulates permits for discharges into bodies of water. This system requires each polluter to apply for a specific permit for their wastewater discharges, which led to the need for industrial wastewater treatment processes, as discharge water could no longer be released without treatment.[69] The permit also includes monitoring and reporting requirements, which allows the EPA to assess total pollutant volumes entering a waterway.[14] However, over fifty percent of the rivers in the United States still violate pollution standards set by the CWA.[71] CWA and NPDES form the backbone of regulation for controlling surface water pollution in the United States. Additional regulation exists on a state-by-state basis, allowing for more stringent regulation for protected bodies of water.[72] Additional regulation may be enacted to limit pollution that comes from non-point sources, such as agriculture. These non-point sources are the reason for the delayed results from the CWA.[73]

Some economists questioned whether the 1972 law was delivering the promised results of cleaner rivers and lakes, and whether benefits exceeded the costs to society. The United States government has spent over one trillion dollars trying to combat water pollution. In the CWA Congress had declared that the nation's waters were to be free of pollutants by 1983, only eleven years after enactment.[71] In general, water quality has improved nationwide since 1972, but not all pollution has been eliminated. Between 1972 and 2001 there was a 12 percent increase in the number of waterways that are safe for fishing.[71] Data supporting this finding is limited; only 19 percent of the United States’ waterways had been tested for contamination.[73]

See also
Summary information
Clean Water Act programs
Specific topics
General

References
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