An Efate perspective on the new EFSA Drinking Water Treatment Guidance 

The guidance describes how to test for transformation products that may be formed during the treatment of water abstracted for the production drinking water, either from surface water or groundwater. The assessment is aimed at both agrochemicals and biocides, and concerns active substances, as well as their metabolites, that could occur in raw water. Initially renewal applications will be impacted, however all products will be affected within two years of adoption of the guidance. Indeed, there are indications that even before implementation of the guidance itself, Member States may request that this data is provided following recent rulings by the European Court of Justice.

The guidance lays out a nice stepwise approach for applicants to follow.

Step 1 of the new guidance requires no placing of studies and can be started immediately. Following the FOCUS modelling of active substances and their relevant metabolites (according to 1107/2009), all substances present at ≥0.1 µg/L are considered relevant for assessment under this new guidance. For groundwater, this threshold already exists, so all active substances in this compartment should be unaffected, however metabolites previously deemed non-relevant may now be triggered. In surface water, often few toxicity issues are found for metabolites past FOCUS Step 2, hence predicted environmental concentrations (PECs) can be well above 0.1 µg/L. While dilution factors can be taken into account at this stage, and in surface water it is the 4 day time weighted average PEC that matters, there will still be many metabolites that would trigger the requirement to go to Step 2.

At Step 2 of the new guidance, the next phase is the prediction of potential transformation products (TPs) for each substance (including metabolites). Options available at this step are modelling using QSARs and/or a literature review. However, it is noted in the guidance that no models yet exist that can predict the exact outcome of the chlorination or ozonation of a substance, so realistically Step 2 is only to guide what is needed to be done at Step 3.

Step 3 and Step 4 are your experimental stages, where laboratory studies are required to be carried out at high and then low concentrations. While there are no OECD guidelines yet for these studies, the water treatment guideline does offer outlines for laboratory experiments to be done. If at Step 4 your TP is identified at ≥0.075 µg/L, you will need to go to Step 5 and identify your TP. You will then need to go to Step 6 and do a full assessment of genotoxicity and general toxicity, which can be quite costly.

At Enviresearch, we offer early stage-screening to check your portfolio of active substances and product uses. We will thoroughly explore the available options to stay within the threshold at Step 1 of the assessment. Using Acre (our time and cost-efficient solution for automation of the FOCUS surface water modelling) we can efficiently scan the PEC values for large numbers of actives, metabolites and refinement options. Allowing you to quickly assess how your product portfolio may be affected, and what cost-effective options are available to reduce the impact. We also offer assessments using QSARs at Step 2, as well as literature reviews, and we can assist with the placing and monitoring of studies at Steps 3 to 5. Please do get in touch if you have any questions.