Pollution, bacteria, violent currents… what are the risks of swimming in water not intended for this purpose ?

Pollution, bacteria, violent currents… the risks when swimming are multiple. During the hot weather, it can be tempting to go and cool off in the water, but some precautions should be taken.

For months, the quality of the Seine water has been on everyone's lips, but what are the real risks of swimming in water that is not designed for this purpose? ?

“We are much more demanding for drinking water and swimming pool water than for bathing water”, warns Bernard Legube, professor emeritus at the University of Poitiers, specialist in water physico-chemistry and water treatment, interviewed by Le Monde.

The concentration of bacteria increases considerably during heavy rain. This can cause wastewater to overflow, as in Marseille, at the mouth of the coastal river called "Epluchures Beach" or in the Seine in recent months. Conversely, in cases of extreme heat, algae and microalgae increase and can be harmful.

Gastroenteritis, swimmer's dermatitis, leptospirosis or poisoning

There may be gastroenteritis caused by feces. Swimmer's itch or ​​"duck flea", caused by parasites present in mallards and swans, which creates itching.

There is also leptospirosis, transmitted by rodent urine, which can cause vomiting, fever, headaches and diarrhea. Finally, there is cyanobacterial toxin poisoning, which causes skin irritations, digestive and nervous disorders. This is more common in the south of France in less oxygenated and slow-flowing waters such as the Tarn.

Pollution is a major issue in water contamination. The consequences of human activities can be dramatic and are still poorly monitored at the national level.

It is possible to find out about the quality of bathing water on a website of the Ministry of Health.

Leading cause of accidental death among under-25s

Accidental drownings, particularly in rivers and bodies of water, are responsible for around 1,000 deaths each year. It is the leading cause of death by accident in everyday life among those under 25, according to Public Health France.

The Loire is particularly dangerous for swimming, as are the Rhône and the Saône, in Lyon. At sea, it is on the coasts of the South-West that the baïnes (depressions on the beaches creating strong currents with the tide) are dangerous.

“It is strongly advised not to swim if there is a strong current”, recalls Marc Valmassoni, campaign coordinator of the non-governmental organization (NGO) Surfrider, which monitors recreational waters and campaigns for their better quality.