If biocides find their way into water, they can have an ecotoxic effect. For a long time, agriculture was considered to be the main cause of water pollution. New investigations have revealed, however, that a proportion of organic pollutants originate in residential areas.
If biocides find their way into water, they can have an ecotoxic effect on algae, aquatic plants and animals from a certain threshold concentration. For instance, they inhibit DNA synthesis or photosynthesis, which is of vital importance to plants. Depending on their fields of application, these organic compounds are called pesticides or biocides, and they are subject to different kinds of regulations. Pesticides are used in agriculture, parks and gardens and are regulated by the Ordinance on Plant Protection Products. The application of biocides includes pest control and material protection and is subject to regulation by the Ordinance on Biocidal Products. There are agents that are used as both pesticides and biocides.
For a long time, agriculture was regarded as the most important source of biocides in the environment. Meanwhile, however, agents have been discovered in the aquatic environment that are no longer permissible in agriculture or whose seasonal occurrence does not correlate with their utilisation on fields. More recent investigations have revealed that some of these substances also originate in residential areas, where they are used, for example, in anti-algal and anti-fungal paints and plasters for modern façades.
Ecotoxic impact on aquatic creatures
As a rule, biocides are leached out of façade materials by rain. In cases of strong precipitation, such rainwater may reach the aquatic environment untreated. Wastewater from façades of newly constructed, heat-insulated buildings carries high concentrations of biocides that frequently exceed the threshold concentrations for an impact on aquatic organisms. Dilution in streams sometimes fails to ensure compliance with admissible benchmarks of the Water Protection Ordinance. Some agents are also known to have an ecotoxic effect even in low concentrations. In addition, the effects caused by interactions between different substances must also be taken into account.
Learning from previous experience
Owing to the improved heat insulation of buildings, it must be expected that the use of biocides in façade coatings will increase further. Moreover eaves, which reduce the leaching-out process, are built less and less frequently, which means that biocides are leached out more quickly. The Ordinance on Biocidal Products has lacunae with regard to material protection agents such as façade paints since a direct movement of such substances from façades to the aquatic environment is not taken into account. The way in which biocides are used in material protection should be based on experience with plant protection products to prevent yesterday’s pesticides from protecting tomorrow’s buildings.
