The DROPLET model is used within the risk assessment to evaluate whether the active substance exceeds the drinking water limit (0.1 μg/L) at the abstraction points of surface water intended for drinking water production.
DROPLET is a pre-registration model, which is used in the assessment of the first product based on an active substance that is new to the Netherlands, and any other substance assessments in the first 3 years from the first authorisation of the active substance in question in the Netherlands. After this period, the assessment will be done on the basis of monitoring data. For more details on the assessment methodology see our Evaluation Manual Chapter 5 Fate and behaviour in water, NL Part, section 2.3.2 and Appendix 3.
Based on model calculations of the FOCUS surface water model (FOCUS D3 ditch scenario using Dutch drift values), downstream concentrations in surface water abstraction points for the production of drinking water are calculated using DROPLET. In DROPLET 1.4.2 an error of version 1.3.2 of April 2023 has been corrected, considering the conversion of the Arrhenius activation energy for transformation in water and sediment; see details.
In addition, DROPLET 1.4.2 now also runs under Windows 11. Since the current version of DROPLET (version 1.3.2) only works on Windows 10, for which support by Microsoft will end soon, it is necessary to have the new version of DROPLET take effect immediately. For ongoing applications for authorisation of plant protection products, the assessment provided by the applicant will be repeated by the Ctgb with the new version of DROPLET; it is expected that this will not change the conclusion regarding the drinking water criterion. We ask applicants to use DROPLET 1.4.2. as soon as possible. It will be obligatory to use this version for dossiers submitted from January 1st 2026; also in dossiers submitted in response to supplementary questions on the assessment of the drinking water criterion. The National addendum template Part B Section 8 Environmental Fate has been adapted to reflect this change.
Ctgb analysed how many decisions were taken in which the previous version of DROPLET was used. This concerned only four dossiers for plant protection products, based on the same active substance. This active substance is now already for more than three years authorised in the Netherlands. Therefore, a pre-registration assessment based on DROPLET 1.4.2. is no longer relevant. The available monitoring data show that the substance does not exceed the drinking water limit.