Water pollution is one of the most serious environmental threats of the 21st century. The U.S. Geological Survey estimates that Americans use 408 billion gallons per day of both fresh and salt water, with fresh water being the majority. Freshwater is used in irrigation, for livestock and for other uses that can affect humans. According to AmericanRivers.org, nearly 40 percent of American waterways are too polluted to support recreational activities such as fishing and swimming.
Pharmaceutical Waste
One of the primary concerns over pollutants are their effects on drinking water. Surface water, such as lakes and streams, is a significant source of drinking water. The New York Department of Health, for example, estimates that more than 50 percent of its state residents depend upon surface water sources. As assessment of U.S. waterways by the U.S. Geological Survey found that 80 percent of the streams sampled contained some pharmaceutical waste. These findings present a risk of human health effects, depending upon what drugs a person is already taking and their possible interactions.
Agricultural Runoff
Water pollution can have many sources, which complicates the reduction of chemical pollutants entering the waterways. According to the U.S. Environmental Protection Agency, agricultural runoff is the primary source of water pollution in the United States.The main types of pollutants include pesticides, fertilizers and animal waste. Pesticides are agents meant to kill a particular pest. The chemical mixture can include toxins that can potentially harm any organism that comes in contact with them. Fertilizers pollute water by disrupting the chemical balance of waterways through introduction of nitrogen, phosphorus or phosphate. Animal waste contaminates water with bacteria, which can sometimes cause human health problems.
Urban Runoff
The effects vary with the nature of the pollutant. Another source of chemical contaminants is urban runoff. The high amount of impervious urban surfaces, such as roads and parking lots, allows water to travel quickly over these surfaces, introducing road contaminants such as gasoline, engine oil and salt into the waterways.
Industrial Contaminants
Some chemical pollutants enter water resources through the air. Chemicals such as sulfur dioxide and nitrogen oxide from industrial emissions combine with moisture in the air to create acid rain. Acid rain chemically alters the pH of surface water to levels too acidic for plants and animals to live. Other pollutants, such as mercury, pose long-term health risks because these toxins do not break down in the environment. Rather, they accumulate in animal tissues, compounding the dangers of water pollution.
Heavy Metals
Other industrial activities such as mining introduce heavy metals into the water resources. Like other industrial waste, heavy metals such as cadmium persist in the environment, requiring removal or mitigation of their effects. If action is not taken, they can accumulate over time, which will increase their toxicity levels. Affected surface water may become an ecological dead zone, unable to support any life. Complicating cleanup is the fact that removal may stir up heavy metals buried in the sediment, causing further environmental issues.
References
- USGS: Surface Water Use in the United States
- American Rivers: River Facts
- New York State Department of Health: Drinking Water Program: Facts and Figures
- U.S. Environmental Protection Agency: Protecting Water Quality from Agricultural Runoff
- U.S. Geological Survey: Pharmaceuticals, Hormones, and Other Organic Wastewater Contaminants in U.S. Streams
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