Recent samples taken at Loch an Duna, Bragar, Isle of Lewis have indicated the presence of blue-green algae, says Comhairle nan Eilean Siar.
Swallowing the water or algal scum can cause stomach upsets or more serious health effects.
Contact with the water or algal scum can cause skin problems.
It is a sensible precaution for you, your children and your animals to avoid contact with the scum and the water close to it.
Dog owners are advised not to let their dogs into the water.
As a precautionary measure, notices will be posted next to the loch warning that contact with the algal scum should be avoided.
Adjoining landowners and fishing interests have been advised of the situation as have NHS Western Isles and Comhairle nan Eilean Siar's Consumer & Environmental Services Section
Blue-green algae exist in fresh waters in Great Britain and throughout the world; they are noticed when their concentrations increase to form “blooms” and when they form scums – looking like blue-green paint – or when they collect on the shore line.
Some blue-green algae may give rise to adverse medical effects – but not always. Effects on people coming into contact with toxic scums include skin rashes, eye irritations, vomiting and diarrhoea, fever and pains in muscles and joints. Toxic algae have caused deaths of livestock and dogs. The treatment of water supplies removes blue-green algae and additional treatment may be applied to destroy or remove toxins should they arise. The actions currently taken are precautionary. The behaviour of algae is erratic and the level of toxicity can fluctuate; it can appear one day, be dispersed by the wind and mixing and reaccumulate at any time.
For further information, contact the Environmental Health Team of Comhairle Nan Eilean Siar on 01851 822 694 (please leave a voicemail)