Standardisation of the combined algae test

Herbicides are used both in agriculture for weed control and in urban areas as biocides to protect building facades, and they pollute watercourses. Within the class of herbicides, so-called photosystem II (PSII) inhibitors constitute an important group. As these substances are toxic to algae and aquatic plants, several PSII inhibitors are listed as priority substances with environmental quality criteria in both the EU and Switzerland. The combined algae test allows for a precise assessment of the effects of mixtures of such PSII inhibitors. We have successfully used the test over many years and within the framework of a wide range of projects; there is also considerable international interest in the test. Several laboratories from Finland, Germany and France have therefore attended training sessions at our facility in Dübendorf. To support the further integration of the method into regulatory frameworks such as the Swiss modular approach or the EU Water Framework Directive, we are now aiming for ISO standardisation of the test.