Bathing is risk-free in supervised areas where the water complies with regulatory standards. During the bathing season, the local health authorities inspect all bathing areas. The results of the resulting bathing water analysis are posted near the beaches. Don’t go uninformed!
In contrast, when water quality has deteriorated, it can affect human health, most often mildly, via skin contact or water that is inhaled or ingested. ? link to Risks resulting from related activities)
The chemical quality of bathing water is generally stable. Barring exceptional circumstances (pollution by accidental spill, for instance), it is therefore not a bathing hazard.
Microbiological pollution in bathing water is most often of faecal origin. Household wastewater, animal excrement and livestock effluents discharged into the environment, polluting bathing sites, can be the cause for poor quality.
Rain can also cause overflowing from collection or treatment facilities intended for wastewater or significant surface runoff.
Health disorders due to microbiological water quality is generally benign (i.e., stomach flu, eye/throat/nose infections), unless pathogens are involved.
In freshwater bathing, wild (mainly rodents) or domestic mammals (livestock, dogs, etc.) are a special risk when infected by one bacteria: leptospira, a bacteria that can lead to leptospirose, the outcome of which is generally positive, provided appropriate treatment, applied to water or humans.
In rivers, downstream from industrial hot water disposal facilities, the high temperatures are conducive to the development of amoeba, some of which can cause brain disease. This occurs only in very rare cases, however, and as of this day, no such cases have been reported in France.
In artificial water bodies, parasites can be found, borne by water fowl (in particular ducks) and develop when the water temperature is high enough (from 25°C). The micro-organisms cause dermatitis, which can lead to severe itching, but are generally benign.
In both saltwater and freshwater, sunlight, temperature and water composition can all foster microscopic algae blooms (phytoplankton or plankton algae), responsible for “coloured water” phenomena, in which the water appears green, red or brown. Some of the algae generate toxins that can lead, in certain concentrations, to impaired health, with varying degrees of seriousness, depending on the types of algae present.