;Total phosphorus and phosphate, 
Phosphates enter surface waters through both nonpoint sources and point sources. Nonpoint source (NPS) pollution refers to water pollution from diffuse sources. Nonpoint source pollution can be contrasted with point source pollution, where discharges occur to a body of water at a single location. The nonpoint sources of phosphates include natural decomposition of rocks and minerals, stormwater runoff, agricultural pollution, erosion and sedimentation, atmospheric deposition, and direct input by animals/wildlife. Point sources of phosphorus may include municipal sewage treatment plants and industrial dischargers. In general, the nonpoint source pollution typically is significantly higher than the point sources of pollution. Therefore, the key to sound management is to limit the input from both point and nonpoint sources of phosphate. High concentration of phosphate in water bodies is an indication of pollution and largely responsible for eutrophication.
Phosphates are not toxic to people or animals unless they are present in very high levels. Digestive problems could occur from extremely high levels of phosphate.
The following criteria for total phosphorus were recommended by the U.S. Environmental Protection Agency.
# No more than 0.1 mg/L for streams which do not empty into reservoirs,
# No more than 0.05 mg/L for streams discharging into reservoirs, and
# No more than 0.025 mg/L for reservoirs.
Phosphorus is normally low (< 1 mg/L) in clean potable water sources and usually not regulated;