Water pollution is any physical, biological, or chemical change in water quality that adversely affects living organisms or makes water unsuitable for desired uses.
Among the many environmental problems that offend and concern people, perhaps none is as powerful and dramatic as water pollution. Complicating the problem is the fact that a change that adversely affects one organism can be advantageous to another. For example, damming of rivers or lakes can affect what plant and animal life remains underwater. This, in turn, can cause fish that survive on the organisms to decline in numbers. If birds and other wildlife rely on the fish for their diets, soon they can decline in number. All events can change the makeup and quality of the water, which also can affect people. There are natural sources of water contamination, such as poison springs, oil seeps, and sedimentation from erosion, but most discussions of water pollution focus on human-caused changes that affect water quality or usability.
For developing countries, the situation is more serious. Globally, about 2.3 billion people have no access to sanitation facilities, such as toilets. Conditions are generally worse in remote, rural areas where sewer systems and waste water treatment are ineffective or nonexistent, and purified water is either unavailable or too expensive to obtain. In the 33 poorest countries, 60% of the urban population have access to clean drinking water, but only 20% of people living in rural areas do. Having safely managed sanitation services can lessen water pollution.
A lack of pollution control is reflected in surface and groundwater quality in countries without the resources or political will to enforce pollution control. In Poland, for example, up to 95% of all surface water is unfit to drink. The Vistula River, which winds through the country's most heavily industrialized region, is so badly polluted that more than half the river is utterly devoid of life and unsuited even for industrial use. In Russia, the lower Volga River is reported to be on the brink of disaster due to the 300 million tons (272.2 million metric tons) of solid waste and 5 trillion gallons (20 trillion liters) of liquid effluent dumped into it annually.
The least developed countries of South America, Africa, and Asia have even worse water quality. Sewage treatment is either totally lacking or woefully inadequate. Low technological capabilities and little money for pollution control are made even worse by burgeoning populations, rapid urbanization, and the shift of heavy industry from developed countries where pollution, labor and other laws are strict to less developed countries where regulations are more lenient.
In Malaysia, 42 of 50 major rivers are reported to be ecological disasters as a result of contamination and flooding. Residues from palm oil and rubber manufacturing, along with heavy erosion from logging of tropical rain forests, have destroyed all higher forms of life in most of these rivers. In the Philippines, domestic sewage makes up 60%–70% of the total volume of Manila's Pasig River. Thousands of people use the river not only for bathing and washing clothes, but also as their source of drinking and cooking water. Only 63% of groundwater resources in China can be used for drinking water due to high pollution levels, rendering them unsuitable for human consumption.
Water pollution is not just a problem in other countries, but in the United States as well. In 2016, Flint, Michigan, had a public health crisis when drinking water was contaminated by lead. The city of Flint had switched water supplies in 2014 to save money, reverting to one used in the 1960s. The supply pipes were corroded, causing lead to leach into the water. Despite complaints from residents early after the switch, the city government insisted there was no problem. Several months later, Escherichia coli and coliform bacteria were detected in the water, and residents were told to boil water before use. By February 2015, tests showed high levels (104 parts per billion) of lead in the water of a resident's home. The EPA limit for lead is 15 parts per billion. A state agency notified the EPA that the city had not followed controls to prevent pipe corrosion. Within the year, problems with lead were brought up and then downplayed. By December, the mayor and President Barack Obama had declared a state of emergency. As of 2018, lawsuits had been filed, a criminal investigation started, and residents had reported having high lead levels in their water, including a near doubling of the lead levels in children. Flint switched back to another water supply.
Other problems occur even in ocean waters. Seaside rural towns in developing nations rely on coastal waters for dumping of human wastes. The Great Pacific Garbage Patch is the largest collection of marine debris. Two large areas of debris swirl in the ocean, one off the coast of California, and one closer to Japan. Natural disasters also can create water pollution. When a giant tsunami hit the Fukushima Nuclear Power Plant in Japan in 2011, toxic waste was released. At least 2 million people in Puerto Rico were at risk of disease from waterborne pathogens months after Hurricane Maria struck the island in September 2017, affecting 70% of the island's water treatment and distribution systems.
Desert soils often contain high salt concentrations that can be moved around by irrigation and concentrated by evaporation, reaching levels that are toxic for plants and animals. Salt levels in the San Joaquin River in central California rose about 50% from 1930 to 1970 as a result of agricultural runoff. Salinity levels in the Colorado River and surrounding farm fields had become so high that millions of acres of previously valuable cropland were abandoned. The United States constructed a huge desalination plant at Yuma, Arizona, to reduce salinity in the river. In northern states, millions of tons of sodium chloride (NaCl) and calcium chloride (CaCl2) are used to melt road ice in the winter. The corrosive effect on highways and automobiles and the toxic effects on vegetation are enormous. Leaching of road salts into surface waters has a similarly devastating effect on aquatic ecosystems.
Acids are released by mining and as by-products of industrial processes, such as leather tanning, metal smelting and plating, petroleum distillation, and organic chemical synthesis. Coal mining is an especially important source of acid water pollution. Sulfides (S2-) in coal are solubilized to make sulfuric acid. Thousands of miles of streams in the United States have been poisoned by acids and metals, some so severely that they are essentially lifeless.
Thousands of different natural and synthetic organic chemicals are used in the chemical industry to make pesticides, plastics, pharmaceuticals, pigments, and other products that people use in everyday life. Many of these chemicals are highly toxic. Exposure to very low concentrations can cause birth defects, genetic disorders, cancer, and can affect reproductive development. Some synthetic chemicals are resistant to degradation, allowing them to persist in the environment for many years. Contamination of surface waters and groundwater by these chemicals is a serious threat to human health.
Hundreds of millions of tons of hazardous organic wastes are thought to be stored in dumps, landfills, lagoons, and underground tanks in the United States. Many, perhaps most, of these sites are leaking toxic chemicals into surface waters, groundwater, or both. The Environmental Protection Agency (EPA) estimates that as of 2018, about 26,000 hazardous waste sites require cleanup because they pose an imminent threat to public health, mostly through water pollution.
In addition to pollution from natural sources and industrial runoff, the possible intentional pollution of water supplies and resources is a recognized vulnerability and an area of concern for scientists and security specialists.
Although the oceans are vast, unmistakable signs of human abuse can be seen even in the most remote places. Garbage and human wastes from coastal cities are dumped into the ocean. Silt, fertilizers, and pesticides from farm fields smother coral reefs, coastal spawning beds, and result in eutrophication (excess nutrient deposition into bodies of water altering water quality) of estuaries. Every year millions of tons of plastic litter and discarded fishing nets entangle aquatic organisms, dooming them to a slow death. Generally coastal areas, where the highest concentrations of sea life are found and human activities take place, are most critically affected. Solid wastes and toxic substances derived from discarded computers and other types of electronics (e-waste) are also a growing concerns.
The Federal Water Pollution Control Act was passed in 1972 to “restore and maintain the physical, chemical, and biological integrity of the nation's waters by preventing point and nonpoint pollution sources, providing assistance to publicly owned treatment works for the improvement of wastewater treatment, and maintaining the integrity of wetlands.” This act, more commonly referred to as the Clean Water Act (CWA), regulates both direct and indirect discharges of the 126 priority pollutants, conventional pollutants (e.g., total suspended soils, oils), and non-conventional pollutants, which are any pollutants not included in the two former categories. The National Pollutant Discharge Elimination System (NPDES) regulates direct (or point source) discharges of pollutants. A permit must be obtained to discharge pollutants into navigable waters after review of analytical data provided by the applicant detailing the pollutant content of the effluent (treated water).
In spite of the enormous bad news about water quality, some encouraging pollution control stories were emerging. The United Nations led efforts in 2014 toward Sustainable Development Goals (SDGs). The SDGs are part of the 2030 Agenda for Sustainable Development, a plan adopted by world leaders to end poverty and inequality around the world, improve health, and address climate change and pollution. The SDGs are not laws but serve as a framework for governments to use in setting their own goals and plans. A total of 17 goals address these global issues. Goal 6 focuses on ensuring access to water and sanitation for all by 2030.
See also Clean Water Act (1972, 1977, 1987) ; Hazardous waste ; Ocean waste .
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Environmental Protection Agency, 1200 Pennsylvania Ave. NW, Washington, DC, 20460, https://www.epa.gov .
William P. Cunningham
Alison C. Heimer, MA
Revised by Teresa G. Odle, BA, ELS