On Friday 19 August 2022, Luxembourg's Ministry of Health has issued an alert concerning the presence of cyanobacteria, also known as "blue-green algae", in the Moselle.
Cyanobacteria have been discovered in various places along the Moselle, in particular in places with slow circulation. Such bacteria are normally present in these waters, but, under certain conditions, can grow excessively and form coloured patches (blue-greenish colour or pea-puree colour). Under these conditions, the bacteria can produce toxins that can cause health problems for humans and animals. These problems depend on the amount of toxins absorbed and include skin irritation, headache, nausea, gastroenteritis, cramps, paralysis and liver damage.
The exact cause of this excessive proliferation is not known, but often results from an inadequate supply of nutrients for these bacteria, in the presence of high water temperature.
It is therefore recommended to avoid contact (swimming, water sports) with water in places where these coloured patches are located and to avoid swallowing this water. This recommendation applies to both humans and animals.