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According to the National Oceanographic and Atmospheric Administration, 80 percent of marine pollution comes from land-based sources. The issue, however, is not limited to coastal environments; lakes, rivers, and water tables are affected on a large scale by pollution that comes from agriculture, industry, vehicle emissions, and products used at home every day. Runoff from soils and even pollutants in the air can settle in waterways, creating unsafe conditions for people and wildlife. Pollutants have many ways of making it into the water supply. Some of the most common sources and causes of water pollution in the nation are detailed below.

Runoff from Agricultural Operations

Agriculture represents one of the biggest sources of water pollution in the country. Industrial agriculture operations tend to release large amounts of water and waste from crop production and livestock, causing both water shortages and harmful pollution in nearby areas. The major causes of such pollution include:

  • Nutrients: The U.S. Environmental Protection Agency has cited nutrient pollution as one of the most problematic environmental issues. Nitrates are a common ingredient in fertilizer and can be seriously harmful to babies if present in drinking water. A U.S. Geological Survey (USGS) report in 2010 found that 64 percent of shallow wells studied in urban and agricultural areas had high nitrate levels. Excess nutrients can stunt aquatic plant growth and kill off fish. Such algal blooms can create dead zones as those seen in the Gulf of Mexico, which has been attributed to nitrogen fertilizer used in Mississippi River Basin croplands.

  • Animal waste: The waste products of livestock, along with chemicals used for farming, get washed away during rainstorms. Water borne diseases such as cholera, typhoid, and dysentery can end up in rivers and water supplies. About 500 million tons of manure are produced every year from animal feeding operations, which is triple the sewage that humans release into the environment, according to a United States Commission on Ocean Policy report.

  • Antibiotics/hormones: Both are commonly supplied to livestock, and subsequently excreted into the environment. Studies have found hormones remain active for months after excretion, traveling for miles downstream and affecting reproduction in fish. Antibiotics that make it into waterways can contribute to the proliferation of antibiotic-resistant bacteria.

  • Heavy metals: Zinc and copper are often used to boost growth in cattle and poultry. Excreted in their waste, such metals and others including lead, chromium, and arsenic end up in soil fertilizer, which runs off into water sources. Heavy metal exposure can lead to kidney, nervous system, and cardiovascular problems.

  • Salts: Sodium, potassium, calcium, sulfate, bicarbonate, nitrate, and other salts in manure can make it into waterways, increasing salinity, altering ecosystems, and making drinking water unsafe.

Runoff and Nonpoint Source Pollution

Rain and melted snow moving above and through the ground take any pollutants with them. Runoff from farms, cities, suburban and rural homes, parking lots, and forests can contaminate waters far downstream. Chemicals to kill weeds on lawns and even road salt to melt ice on roads can end up in the water. Stormwater-related runoff can increase sediment in navigable waterways and pollute drinking supplies. In fact, according to the Commission on Ocean Policy, an inch of rain over a one-acre paved parking lot can produce 16 times more runoff than the same amount on a natural meadow the same size.

Industrial Activities

Industrial operations often drain waste into fresh water supplies. Toxic chemicals increase the number of minerals in, change the color of, and cause temperature changes in water. Pollutants such as mercury, asbestos, nitrates, and lead may be released. Major processes contributing to the problem include:

  • Mining: Crushing rock, extracting coal and minerals, and other activities release harmful chemicals and toxins, including sulfides from rocks and metal waste that mix with water.

  • Fossil fuel burning: Produces ash (with toxic chemicals) that mixes with water vapor, creating acid rain that eventually makes it to water sources.

  • Foundries: Metals and particulates can be emitted directly into the air and eventually find their way into bodies of water or the ground where they can run off.

  • Wastewater treatment: Industrial, commercial, and residential wastewater treatment is designed to remove most solids, pathogens, and organic materials. The effluent released into local waters isn’t always free of bacteria, viruses, sediment, metals, and other pollutants as it should be.

Leakage from Underground Storage and Piping

Transporting coal and other industrial and petroleum products carries the risk of leaks in underground storage systems and pipes. Heavy use and corrosion can lead to spills. Accidental leakage can also occur during any part of the transportation process, leading to soil and water pollution.

Leaking Sewers

Sewer system overflows are major point sources of water pollution. If a sewer overflows, its contents can enter waters before it is treated. There are 40,000 sewer overflows per year, the EPA has estimated. The discharge can go directly into oceans, rivers, and estuaries, affecting human health, shell fishing, and causing beach closures. Improperly managed septic systems present pollution problems as well for coastal areas.

Vehicle Emissions

Atmospheric emissions from motor vehicles can settle or make their way to surface and ground water through rain. Oil left behind by a parked car can run off. Visible as a colorful sheen in puddles, automotive oil can become a nonpoint source pollutant that drains into streams, lakes, rivers, and oceans.

Landfill Leakage

If a protective bottom layer is missing or damaged, contaminants can leak into groundwater. The Groundwater Foundation reveals landfills as a source of household cleaners, battery acid, and other compounds that can lead to water pollution

Hazardous Waste

There are more than 20,000 uncontrolled hazardous waste sites in the nation, according to the USGS. Barrels and containers may leak as they age. Leaking contaminants can eventually make it into the groundwater through cracks in concrete floors and other barriers.

Radioactive Sources

Leaks from nuclear power plants into water doesn’t only happen in Japan or Russia. Indian Point nuclear power plant on New York’s Hudson River sometimes releases radioactive water that is considered to have permissible levels of contamination, per government regulations ( Over 100 different isotopes are released into the water and air in small amounts, including Iodine-131, Strontium-89, and Strontium-90. These can make it into water and the food chain, as pollutants from agriculture, industry, runoff, vehicles, sewers, and other sources do throughout the U.S.

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