Blue-green algae or cyanobacteria

Water with blue-green algae.

Even good quality bathing water may become contaminated, sometimes as the result of the actions of beach users. Norovirus-induced diarrhoea and vomiting may be the result of swallowing bathing water contaminated by a swimmer’s intestinal microbes during bathing. Noroviruses may spread in a beach environment also through poor hand hygiene due to not washing one’s hands properly after going to the toilet.

Bathing water may become temporarily contaminated for the following reasons:

  • Microbes from the faeces of bathers
  • Wastewater leakage drifting to the beach
  • Faeces of wild animals or livestock on a pasture located close to the beach
  • Stormwater from built-up areas
  • Impurities leached from the soil by heavy rain or floods
  • Chemical pollution, such as an oil spill

Blue-green algae can become abundant if conditions in bathing water are favorable.

Do not use water with blue-green algae

The use of water should always be restricted if blue-green algae is visibly perceptible in the water. Some species of blue-green algae produce toxin. In addition to toxin, blue-green algae are also capable of producing skin irritants. If you suspect that you have been bathing in water containing blue-green algae, wash yourself with clean water after bathing.

If the water contain blue-green algae:

  • The water must not be used as drinking water by humans or animals even after boiling
  • Do not use blue-green algae water in the tub
  • Do not use for washing dishes
  • Do not use for washing
  • Do not use in the sauna
  • Do not use in the irrigation of edible plants
  • Bathing in water containing algae should be avoided, and children and pets must not be allowed in the water.

Blue-green algae may cause red or itchy skin, oral or nasal symptoms, vomiting and diarrhoea. The symptoms usually manifest within a few hours of exposure to blue-green algae. If symptoms of exposure to blue-green algae are detected, the skin and eyes must be washed thoroughly with plenty of clean water. If necessary, the Poison Information Centre provides further instructions, tel. +358 800 147 111.