What Is Water Pollution? A Clear Look at the Causes and Effects

, Staff Writer
Updated April 23, 2021
water pollution green sea turtle entangled in discarded fishing net
    water pollution green sea turtle entangled in discarded fishing net
    Aryfahmed / iStock / Getty Images Plus
    Used under Getty Images license

Water pollution is a serious environmental issue. The presence of pollutants in bodies of water leads to many negative impacts, such as the proliferation of disease, contamination of drinking water and the food chain, and destruction of biodiversity. Learn more about what is water pollution and how it is caused.

What Is Water Pollution?

Water pollution occurs when a body of water is contaminated by harmful substances. Contamination can result from chemicals, microorganisms or other toxic substances being introduced into a body of water. Water pollution can occur in all types of bodies of water, including seas, oceans, rivers, lakes, creeks, and ponds. Water pollution can also occur in the form of groundwater contamination.


Major Causes of Water Pollution

There are many causes of water pollution. Discover several common sources of water pollution.

Agricultural Operations

Industrial agricultural operations are a significant source of water pollution. Waste produced on agricultural sites washes into the groundwater when it rains. When located near the water, this waste can get directly into the drinking water supply. This waste can include nitrates from fertilizer, animal waste that may carry cholera, dysentery and typhoid, or the antibiotics or hormones often used to treat livestock.

Industrial Waste

The waste produced at industrial sites, such as manufacturing or power generation plants, can cause water pollution. Such locations often produce toxic chemicals or other pollutants as a by-product of their operations. While these organizations are heavily regulated, there have been cases where improperly treated industrial waste is dumped into the freshwater supply. Such waste also sometimes gets into the water supply via leakage or spilling, due to compromised containment systems.


Marine Dumping

Marine dumping is deliberately dumping garbage or waste into the oceans, seas or other bodies of water. It involves all kinds of dumping, from recreational boaters who throw trash overboard to the dumping of large quantities of garbage, industrial waste or other substances into the water. A good bit of marine dumping occurs as a result of dredging, which is the procedure to maintain the depth of rivers, canals and harbors.


All "used" water is considered wastewater, such as the water from your sink, shower, dishwasher, or washing machine. Water that contains urine or feces is sewage. Both types of water pass from homes and businesses to sewage and wastewater treatment plants, where pollutants are reduced. However, even after being treated, sewage and wastewater still contain dangerous substances like nitrogen, phosphorus, heavy metals, and various pathogens. According to the United Nations, more than 80% of sewage and wastewater is released back into the environment.


Oil Pollution

Oil accounts for a lot of the pollution in the oceans, seas and other bodies of water. Some is the result of catastrophic oil spills that occur, but it's not only events like this that lead to this type of water pollution. Boats and ships often drip oil as they go about their daily outings. When cars, trucks and motorcycles leak gasoline onto roads, it washes into nearby water supplies via stormwater runoff. No matter how oil gets into the water, it is harmful to marine life and the environment and can also impact people.

Water Pollution: Real-World Examples and Impact

There are far too many real-world examples of water pollution, each leading to devastating effects on people, wildlife and the environment.

  • In 2020, Algoma Central Corporation of Ontario, Canada, pled guilty in a U.S. court for violating the Clean Water Act. While transiting Lake Ontario, the crew of one of its vessels dumped a wash water tank with almost 12,000 gallons of oil-tainted water into the U.S. portion of the lake. Oil discharge into water can kill marine life and introduce toxic substances that get into the food supply.
  • The 2010 Deepwater Horizon Oil spill is the largest oil spill ever. This spill released 210 million gallons of oil into the Gulf of Mexico for 87 consecutive days. Many marine animals and birds died and continue to suffer long-term impacts. Desiccants used in the clean-up are believed to have impacted groundwater in the affected area.
  • In 2010, Cooperative Success Maritime S.A. was fined and put on probation after it was discovered that one of its vessels was deliberately dumping oil-contaminated waste into the ocean. This took place at least ten times within a six-month timeframe. A crew member blew the whistle when the Coast Guard boarded the vessel for inspection.
  • In 2008,1.5 million tons of coal ash, containing arsenic, lead, mercury, and radium, spilled from a power plant in Kingston, Tennessee. It got into two rivers, covered hundreds of acres of land, and flooded a few dozen homes. Clean-up workers and their families are still suffering ill effects from their exposure to coal ash, including heart disease, birth defects, organ damage, and cancer.
  • The movie Erin Brockovich was based on the true story in which Pacific Gas & Electric was held liable for dumping chromium-6, a known carcinogen, into a pond in Hinkley, California. The dumping took place during the 1950s and 60s. It got into the town's water supply, leading to extremely high instances of cancer and other incidents. Town residents won their lawsuit in 1996.
  • Monsanto has been held liable in many lawsuits for polluting water supplies with polychlorinated biphenyl (PCB). One example is Anniston, Alabama, where the company produced and knowingly released harmful PCBs into the environment for more than 40 years. PCBs can accumulate in the body over time and cause cancer, skin lesions and liver damage.
  • In 1989, the Exxon Valdez oil tanker spilled 11 million gallons of oil into the Gulf of Alaska. Since that time, the affected area has experienced a decline in fish and wildlife populations, receding ice and warming water temperatures

Environmental Protection Matters

Water pollution is very harmful. Even though many regulations have been put in place over the years to reduce its occurrence, it is still a serious problem. Now that you are more aware of the causes and effects of water pollution, take the time to educate yourself on other important environmental issues. Start by exploring what land pollution is. Then, explore air pollution.