1. Water Quality Problems Related To Nutrient Pollution

Nutrients like nitrogen (N) and phosphorus (P), whether from farms, city streets, or sewage treatment plants, are responsible for many water quality problems across the United States. In the National Water Quality Inventory: 1998 Report to Congress, the Environmental Protection Agency estimated that more than 3.5 million acres of U.S. lakes, 84,000 miles of U.S. rivers, and 2900 miles of estuaries are significantly affected by nutrient pollution. Some of the most important water quality problems associated with nutrient pollution include:

• Fertilizing Surface Waters. Eutrophication is the over-fertilization of lakes, estuaries, and coastal waters by too much N and P. In lakes, eutrophication causes algae blooms, excessive growth of aquatic weeds, and drastic changes in the populations of fish and other aquatic animals. These changes often interfere with use of the water for recreation, fishing, or water supply. In water supply reservoirs, for example, algae blooms can cause taste and odor problems that are very costly to control. High algae levels in unfiltered drinking water sources can increase the need to chlorinate, raising the risk of the production of carcinogenic chlorination by-products. Accelerated eutrophication has impaired water quality for human use and aquatic life support in the Great Lakes, Lake Champlain, Lake Okeechobee, and numerous smaller lakes and reservoirs across North America.
  
  
• Loss of Oxygen. Hypoxia, a loss of oxygen in estuaries and coastal waters due to excess plant growth, is devastating to marine life. Episodes of hypoxia occur regularly in U.S. estuaries and coastal waters such as the Gulf of Mexico and Long Island Sound. The largest hypoxic zone in the United States forms every spring and summer in the Gulf of Mexico just west of the mouth of the Mississippi River. In 1999, the hypoxic zone was the biggest ever measured at 7,700 square miles, or roughly the size of the state of New Jersey. In North Carolina, two separate hypoxic events in the Neuse River Estuary in 1995 killed millions of fish. In the Chesapeake Bay, low oxygen levels have killed many blue crabs, one of the most popular local menu items.
  
  
  
  
  
  
• Obnoxious Algae Blooms. Blue-green algae (Cyanobacteria) and Pfiesteria are potentially dangerous microorganisms promoted by excessive nutrient supplies in lakes or coastal waters. Blooms of toxic blue-green algae associated with eutrophication have been reported in Lake Champlain (VT), in Lake Erie's western basin (OH), Lake Sammamish (King Co., WA), and elsewhere, threatening children, pets, and livestock. Pfiesteria piscicida has been implicated as a cause of major fish kills at many sites along the U.S. Atlantic coast, including North Carolina's New River and the Albemarle-Pamlico estuaries and Eastern Shore tributaries of the Chesapeake Bay.
  
  
  
  
  
  
• Health Problems. A potentially fatal condition known as Methemoglobinemia ("blue-baby syndrome") can result from high nitrate (NO₃) levels in drinking water from excess nitrogen leaching into ground water. Cases of infant methemoglobinemia associated with contaminated drinking water have been reported in several areas of the U.S., including Nebraska, South Dakota, Colorado, and elsewhere. In 1991 and 1992, a total of 1825 exposures to nitrates—including 542 among children less than 6 years of age—from environmental and other sources were reported to the Association of Poison Control Centers. Nitrates can also be harmful for livestock health.
  
  
  

Last Updated: December 11, 2003 15:09