Groundwater assessment for pesticide registration in Great Britain and Northern Ireland

When you are applying for pesticide registration in Great Britain or Northern Ireland you need to submit a groundwater assessment (PECgw) for the pesticide active substance and any of its metabolites which are formed in soil.

You can conduct a first tier groundwater assessment using the FOCUS groundwater models and the guidance for using these models available at the FOCUS DG SANTE Groundwater webpages.

• First tier assessment of PECgw
• Higher tier assessment of PECgw

If you are applying to a register a pesticide that will be used on hard surfaces, you need to follow the guidance related to HardSPEC: Surface and Groundwater Exposure Model for pesticide registration in Great Britain and Northern Ireland.

If you want to use any methods that deviate from this guidance please contact HSE.

First tier assessment of PECgw

When preparing your submission for pesticide registration (active substance approval and plant protection product authorisation), you must use the following methodology for the initial assessment of groundwater contamination.

Assessment of groundwater contamination from a pesticide and its metabolites uses the FOCUS groundwater models. The models use 9 different soil and weather scenarios to represent different parts of Europe, but only 4 of these are relevant to the UK. Therefore, submissions for Great Britain and Northern Ireland approval or authorisation should only consider the scenarios:

• Chateaudun
• Hamburg
• Kremsmunster
• Okehampton

Detailed guidance on the FOCUS groundwater models, the scenarios and substance data required is available at the FOCUS DG SANTE Groundwater webpages. The model versions and guidance on first tier assessment used in GB and NI are shown on the Environmental fate models (hse.gov.uk) page.

The models are used to simulate the requested pattern of use and predict concentrations in groundwater (PECgw) for the pesticide active substance and its metabolites. The regulatory output of the models is the 80th percentile annual average concentration of each substance in soil water at 1 metre depth. The predicted concentrations are compared to the legal threshold of 0.1 µg/L. Approval of the active substance or authorisations for plant protection products will not normally be possible if the regulatory output of the models for the pesticide active substance is at or above 0.1 µg/L. If the regulatory output of the models for a metabolite is at or above 0.1 µg/L, approval of the active substance or authorisation of the plant protection product may be possible if the metabolite can be shown to be 'not relevant'. The appropriate guidance on determination of the relevance of metabolites in groundwater is the EU SANCO (2021) Relevance of Metabolites in Groundwater guidance, revision 11. Advice on how to use this guidance for GB assessments is provided in HSE pesticides toxicology advice. For approval of active substances, an acceptable groundwater assessment must be demonstrated for at least one use pattern of the associated pesticide product; this is sometimes referred to as 'one safe use'.

Three groundwater models are normally used. Two of these, FOCUS_PEARL and FOCUS_PELMO, should always be used and the results presented. For submissions for approval or authorisation in Great Britain and Northern Ireland, a third model, FOCUS_MACRO, should also be used for any of the crops in the good agricultural practice (GAP) which are in the range of crops included in the 'Chateaudun' scenario. The previous requirement to use FOCUS_MACRO to specifically assess substances with soil adsorption Koc value of 100 mL/g or greater is no longer required. Modelling using only one of the models (usually FOCUS_PEARL or FOCUS_PELMO) is possible when the concentrations of all the substances in the simulation with one model are less than 0.001 µg/L.

Higher tier assessment of PECgw

If the pesticide active substance or one of its soil metabolites fails the first tier groundwater risk assessment, higher tier approaches may be possible using guidance described in the document 'Assessing Potential for Movement of Active Substances and their Metabolites to Ground Water in the EU'. An additional approach is to generate data on 'aged sorption' of a substance in soil. Further guidance on this approach is given in the guidance Aged sorption in groundwater assessment for pesticide registration in Great Britain and Northern Ireland.

At the highest tier of assessment, groundwater monitoring data can be used. Additional guidance which you could utilise in devising monitoring strategies to address regulatory requirements on groundwater contamination is given in a SETAC publication, 'Conducting groundwater monitoring studies in Europe for pesticide active substances and their metabolites in the context of Regulation (EC) 1107/2009'.

It is that you contact HSE pesticides if you need to take a higher tier approach to groundwater assessment.