The New ECHA/EFSA Water Treatment Guidance
The New ECHA/EFSA Water Treatment Guidance
The European Union has taken an important step forward in protecting drinking water with the publication of the new joint ECHA and EFSA Guidance on the impact of water treatment processes on residues of active substances and their metabolites in water intended for human consumption.
Until now, regulatory evaluations focused mainly on the concentration of active substances in raw groundwater or surface water before treatment. The new Guidance changes this significantly because it requires assessing what happens to these residues during water treatment, including filtration, ozonation, chlorination, activated carbon, UV and other steps. These processes can transform active substances into new transformation products, which may have different and sometimes higher toxicological relevance than the parent compound.
This new assessment framework becomes mandatory from the 1st of April 2026 for applications under both the Plant Protection Products Regulation and the Biocidal Products Regulation. From that point onwards, any active substance or product that could lead to residues above 0.1 micrograms per litre at drinking water abstraction points must undergo a structured assessment. This includes environmental modelling, identification of possible transformation products using literature, QSAR tools or laboratory treatment simulations, toxicological evaluation of those products and, if needed, a full human health risk assessment.
For industry this represents a significant challenge. Some substances that are already approved may require new data packages, dossier preparation will take longer and costs for analytical and transformation product testing will increase. The Guidance changes the workflow by extending the risk assessment beyond the environment to include the chemistry inside water treatment plants.
In short, the new ECHA and EFSA Guidance is a game changer. Companies that prepare early will avoid delays and unexpected data requests in 2026 and in the following years. The sooner applicants integrate these requirements into their regulatory strategy, the smoother their future approvals under EU law will be.
If you need advice or assistance with new guidance for plant protection products, biocides or chemicals in the EU and UK, please do not hesitate to contact the experts at Kerona info@kerona.ie