Typically, water monitoring assesses levels of coliform bacteria (bacteria found in several environments, including feces) and sometimes more specifically Escherichiacoli, a type of bacteria found exclusively in feces, as a means of detecting the presence of feces in recreational waters. Since coliforms and E.coli do not survive for very long outside of the intestinal tract, their detection in water is an indication of recent fecal contamination. As a result, local authorities restrict use of water for recreational activities when the bacteria level exceeds standards for safe use.
The bacteria that are tested for are indicators of fecal pollution. They are used for testing because they can be detected quickly and inexpensively. Their presence in the water does not necessarily pose a health danger, since the coliforms may not be disease-causing. However, other bacteria in feces (such as species of Salmonella, Vibrio, and Shigella) can be dangerous. As well, disease-causing viruses can be present in feces.
A beach may be closed when the level of water contamination poses a definite health risk. Mildly polluted water can cause conditions such as a headache, sore throat, or vomiting. Highly polluted water can cause hepatitis, cholera, and typhoid fever.
See also Cholera ; Typhoid fever ; Viruses .
United States Environmental Protection Agency (EPA). “Human Health: Advisories: Swimming Advisories.” http://www.epa.gov/ebtpages/humaadvisoriesswimmingadvisories.html (accessed October 16, 2010).