The purpose of the bathing water classification is to represent ‘the relative risk to the average bather on an average bathing-season day’, using a nationally consistent description which corresponds to a specific ‘probability of contracting a gastrointestinal illness’ during a typical bathing visit.
An excellent classification corresponds to a probability of less than 3%. The regulations describe unacceptable water quality as poor, representing a risk that is greater than 8.4%.
The classification applies for the duration of current bathing season and is re-calculated before the next season, based on water quality monitoring undertaken over the previous four seasons.
The bathing water classification is designed to represent the risks to bathers. It does not represent the risk to visitors engaging in watersports or other recreational activities, and these users might expect a higher degree of risk.
Only risks arising from specific faecal bacteria that cause gastroenteritis, or similar conditions are considered. Classification does not account for other forms of pollution (viruses or chemicals etc), nor does it consider the risk of contracting other forms of illness that may arise from faecal or other bacteria (for example, the infection of wounds or ‘swimmers-ear’).
Bacteria are always present in all coastal waters, originating from agricultural & urban landuses, sewage systems, and natural sources (such as wildlife).
Because bacteria is always present, the risk posed to the health of bathers is never entirely nil. Even at beaches with the very best water quality, a handful of visitors each season will be expected to suffer some negative health effects as a result of their bathing visit.
The risk to bathers on a specific day might exceed that represented by the current bathin water classification, for example, when conditions are poor or when water is affected by faecal pollutants at concentrations lower than is regarded to be pollution.
Where there is pollution, the council would take steps to prevent bathers encountering it – usually by closing the beach.
More information on bathing water classification and bacterial standards can be found via the Environment Agency website.