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What causes nutrient pollution?

Nutrient Pollution Infographic

Nutrient pollution from humans can make HABs much worse. Nitrogen and phosphorus are commonly used in agriculture, lawns, and other human activities. These nutrients can then flow into bays, rivers, and the sea, leading to a buildup that stimulates algal growth (Credit: U.S. Environmental Protection Agency). View and print this infographic and see the description below.

Nitrogen and phosphorus are essential for the growth of algae and aquatic plants, which provide food and habitat for fish, shellfish, and smaller animals that live in water. When too much nitrogen and phosphorus enter the water it causes algae to grow faster than ecosystems can handle. This growth leads to harmful algal blooms, or HABs. Very large increases in algae harm water quality, the food resources, and habitats. HABs can also decrease the oxygen that fish and other aquatic life need to survive.

Many human activities produce excess nitrogen and phosphorus and cause nutrient pollution. Here are a few examples:

  • Agriculture: Animal manure and chemical fertilizers used to grow crops contain nitrogen and phosphorus. However, when farms use too much fertilizer or mis-manage manure, rain events can wash them into waterways.

  • In and Around the Home: Fertilizers, yard and pet waste, and certain soaps and detergents contain nitrogen and phosphorus. These can contribute to nutrient pollution if not properly used or disposed of. The amount of hard surfaces and type of landscaping can also increase the runoff of nitrogen and phosphorus from homes and yards during wet weather.

  • Stormwater: When precipitation falls on our cities and towns, it runs across hard surfaces like rooftops, sidewalks, and roads. That runoff carries pollutants, including nitrogen and phosphorus, into local waterways.

  • Wastewater: Our sewer and septic systems are responsible for treating large quantities of human waste. These systems do not always operate properly or remove enough nitrogen and phosphorus before discharging into waterways.

  • Fossil Fuels: Nitrogen is a byproduct of burning fossil fuels like oil and coal. The combustion of fossil fuels by power plants, large industries, and automobiles is a major source of nutrients in the atmosphere.

Excess nitrogen and phosphorus can travel thousands of miles from inland to coastal areas like the Gulf of Mexico and Chesapeake Bay. Waterways across the U.S. have poor water quality because of nutrient pollution, including:

  • More than 100,000 miles of rivers and streams.

  • Close to 2.5 million acres of lakes, reservoirs, and ponds.

  • More than 800 square miles of bays and estuaries.

River deltas

River deltas like this one in Kachemak Bay, Alaska, can be locations of “dead zones” as a result of algal blooms from nutrient pollution. Other factors—such as the geography of the coast, amounts of runoff, tides and currents, water temperatures, and even other organisms in the water—can all change the scope and severity of HABs and their impacts. (Credit: NOAA).

Infographic Description

Nutrient pollution occurs when there is an excess of nitrogen and phosphorus

  • 50 out of 50 states are impacted by nutrient pollution.
  • States have identified about 15,000 waterbodies in the United States with nutrient-related problems.
  • Reported drinking water violations for nitrates have nearly doubled in the last decade.

Nutrient pollution is widespread

  • Did you know the Mississippi River Basin spans 31 states and ultimately drains into the Gulf of Mexico?
  • The Mississippi River is the largest in the United States and creates the third largest river basin in the world.
  • Nutrient pollution from the Mississippi River Basin is causing a large “dead zone” in the Gulf of Mexico that cannot support aquatic life.

Where does nutrient pollution come from?

Fossil fuels

  • 250 million cars and trucks in the United States release more than 7 million tons of nitrogen oxides into the atmosphere, contributing to pollution in the air and water.


  • Animal manure, excess fertilizer applied to crops and fields, and soil erosion make agriculture a large source of nutrient pollution.
  • Livestock production generates close to 1 billion tons of manure.
  • From 1964 to 2008, agricultural fertilizer use increased by 25%.

Urban sources

  • About 10% of the nutrients flowing from the Gulf of Mexico come from urban stormwater and wastewater/sewage treatment plants.


  • In 2012, 592 industrial facilities released 100,000 tons of nitrate compounds, equal to 3,000 full railroad cars.

Impacts on the nation

Nutrient pollution is one of America’s most serious water pollution issues today. Limiting nutrient pollution will protect people’s health, support the economy, and keep America’s waters safe for swimming and fishing.