Drinking water resources in Germany are largely ground water and bank filtrate or mostly well protected and less eutrophic reservoirs. Therefore, Germany did not implement a guideline value for microcystins or other cyanotoxins in drinking water. In case of (suspected) cyanotoxin contamination Article 6 of the German drinking water ordinance stating that “drinking water should not contain chemicals in concentrations possible harmful to humans” can be applied with the WHO guideline value of 1 µg/l for microcystin as part of the good technical practice.
In Germany the risk from toxic cyanobacteria is more relevant through bathing. A joint working-group of federal and state government develops recommendations to protect bathers from cyanobacteria and cyanotoxins. The current surveillance scheme is largely based on visual inspection and identification of cyanobacteria supplemented with alert levels for biomass and cyanochlorophyll-a as well as microcystin guideline value of 30 µg/l. Its legal status is not mandatory, but it defines good practice and in a court case would serve as reference for expert opinion.
A decision support tool from Germany link