All have been found in ground water and municipal drinking water supplies. In the United States, waste from farm animals is estimated to be 20 times that produced by humans. Fertilizer and nutrients from farmland, household detergents and sewage stimulate excess algae growth in waterways. The algae die, respire and decay. If water has too much organic waste, such as dead algae, bacteria use more dissolved oxygen than usual.
Most aquatic life does well in water with oxygen concentrations of nine parts per million.
Concentrations less than five parts per million will asphyxiate some species. Some industries, such as steel mills, require good water quality for production. Others, such as tourism and commercial fisheries, suffer because of polluted water. Because water pollution can curtail economic growth, lower worker health standards and income can result.