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Beach closings are complex environmental issues with both public health and economic consequences. When bacteria levels at public beaches are found to be “unsafe” for human exposure, local municipal health departments may issue a “no swimming advisory”.
In Ontario, when the provincial standard of 100 colony-forming units (cfu) of e-coli per 100 ml is exceeded, the provincial health officer must close the beach. In Québec, beaches are closed when e-coli counts exceed 200 cfu per 100 ml.
E-coli are an “indicator” bacteria used to assess the potential public health risk of the water. Their presence in surface waters is an indication of fecal pollution. Indicator bacteria do not necessarily pose a direct health risk to humans but do suggest the likely presence of harmful pathogens, such as salmonella, shigella, noraviruses, enteroviruses, cryptosporidium, and giardia, that are found in both human and non-human sources of fecal pollution and are considered health threats.
Exposure to water-borne bacteria increases the risk of adverse health effects such as gastroenteritis, ear, eye and skin infections, and acute respiratory illness. The likelihood of contracting these symptoms increases with the concentration of pollution and length of exposure to polluted water.
High e-coli counts may be caused by stormwater runoff after heavy rain, overflows from combined sewers that carry untreated sewage and stormwater, sewage spills or leaking sewage pipes. Large bird populations have also been blamed for high e-coli counts. Consequently, beach closure signs during the summer are not unusual at the urban beaches in the Ottawa River watershed.
Beach closures are only one result of waterborne pathogens in our waters. These pathogens can also pose threats to our drinking water as well as to aquatic ecosystems and biodiversity.
The cities of Ottawa and Gatineau post their monitoring data from official municipal beach sites.