Active Substance Residues in Drinking Water

Starting April 1, 2026, assessing the impact of water treatment processes on active substances and their metabolites is a new requirement in Europe. Led jointly by the European Chemicals Agency (ECHA) and European Food Safety Authority (EFSA), this initiative applies to new registrations and renewals of active substances in plant protection and biocidal products.

The guidance document on the impact of water treatment processes on residues of active substances or their metabolites in water abstracted for the production of drinking water was published late 2023. Discussions are ongoing between chemical, agrochemical companies, and contract research organizations (CROs) to define and validate clear testing strategies and analytical support to satisfy the new requirements.

Drinking water is gathered from sources including surface water and/or groundwater. The guidance outlines various approaches to measure the impact of water treatment processes on both active substances and their metabolites in the production of drinking water. The guidance covers processes primarily used in the European Union, including filtration, chlorination, pre-oxidation, ozonation and UV disinfection. This will help to address public health concerns around exposure to harmful compounds in drinking water.

What is involved in the testing?

The tiered framework avoids in-life studies where possible and includes the use of weight-of-evidence and new approach methodologies where appropriate.

The exact number of active substances already in use that will need to be assessed is not yet known but is estimated to be somewhere between 100 and 500, with multiple potential metabolites for each of these substances. This is leading to concerns from manufacturers who would be forced to complete testing to ensure ongoing compliance of their products.

How can Charles River help?

Our in-house experts are working closely with existing clients to identify potential testing needs and to ensure capacity is available to support the volume of testing needed to meet the 2026 deadline.

We are ideally placed to support clients and meet their deadlines with our extensive experience in environmental fate and residues. Our in-house analytical teams have expertise in the detection and identification of unknown metabolites and degradants in complex matrices using a variety of platforms and methods, ensuring your samples move seamlessly through your testing and analysis program.

To find out how we can support you in planning and executing the most efficient testing program reach out to our experts.

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