In some cases, substances for which there are no established limit or guideline values are found in drinking water at very low concentrations. The German Environment Agency has developed comprehensive solutions for such cases, and we have collaborated to assess their effectiveness and identify areas for enhancement in their practical implementation.
The presence of a vast array of chemical substances in production and use means that a considerable proportion of them can be detected in nearly all environmental compartments. The existing European and national legal regulations are not yet fully effective in preventing substances that have not yet been assessed from entering the environment. This includes substances that degrade only slowly, are highly water-soluble, and are not or hardly retained by underground passage and drinking water treatment. Furthermore, advancements in instrumental trace analysis are enabling the detection of an increasing number of substances with a high degree of sensitivity. Consequently, substances for which no limit or guideline values exist are found in drinking water in very low concentrations and in a limited way in terms of time and location. In such cases, a timely toxicological assessment is essential.
The German Environment Agency has developed the concept of ‘health-related indication values’ (HRIV, in German: "GOW") for the assessment of substances in drinking water that have not yet been assessed or have only been partially assessed. A GOW is designed to address the discrepancy between the analytical detection of a substance in drinking water above 0.1 μg/L and the presence of a guideline or limit value.
Under the leadership of the IWW, we have collaborated with colleagues from the UBA to assess the HRIV/GOW concept, determining its acceptance and implementation by health authorities. The perspective of the water suppliers, who are directly affected by the official orders and measures when a HRIV/GOW is exceeded, was also included. Extensive surveys of authorities and water supply companies regarding their experiences and subsequent discussions at a workshop at TZW were essential core elements of the project.
It became evident that the regulatory value concepts applied in the drinking water sector are widely accepted and implemented in practice, ensuring a high level of consumer protection. Optimization potential was identified in the areas of a uniform knowledge base, communication, harmonization, availability and access to relevant data, and proactive monitoring. These include an improved range of training courses, timely information events following adjustments, and standardized training formats in which existing assessment concepts, terminology used, and current developments in assessment and enforcement are communicated in a clear and target group-specific manner. New formats, especially digital ones, should be developed to facilitate early dialogue among all involved parties, thereby enhancing cooperation and promoting conflict-free solutions.
The exchange of data from proactive monitoring approaches, which has been limited by data protection so far, can also make a significant contribution to identifying possible risks to water supply at an early stage and at the same time enabling a statement to be made about the extent to which they are affected. In general, proactive monitoring approaches developed thus far hold considerable potential for comprehensive risk assessment, including effect-directed and effect-related analysis.
