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Groundwater

General guidance on data requirements to assess the fate and behaviour as well as environmental exposure of pesticides in Groundwater can be found on the FOCUS website.  A number of environmental exposure modelling tools and guidance documents for use in the EU have been produced by the FOCUS initiative, (FOrum for the Co-ordination of Pesticide Fate Models and their USe).  There are three main FOCUS models used in evaluations (though a fourth, rarely used model, PRZM, is also available)

The current versions of these models are: FOCUS PEARL 4.4.4, FOCUS PELMO 5.5.3 (first released on 11 April 2011) and MACRO 5.5.4 (released on 4th June 2012) respectively.  Guidance for these models can be found on the FOCUS website groundwater section.  The guidance document: Assessing Potential for Movement of Active Substances and their Metabolites to Ground Water in the EU;Commission Guidance Document SANCO/13144/2010, version 3, 10 October 2014 builds on the original report: 'FOCUS Groundwater Scenarios in the EU review of active substances' (SANCO/321/2000 rev.2).  Additional guidance and information can be found in Appendices A to D which includes specification of the FOCUS scenarios and parameterisation of the models: MACRO, PELMO (ver. 3.3.2) and PRZM, with parameterisation of PEARL (ver. 3.3.3) found in Appendix E.

The latest FOCUS guidance document: Generic Guidance for Tier 1 FOCUS Groundwater Assessments (version 2.2), is based on 'FOCUS Groundwater Scenarios in the EU review of active substances' (SANCO/321/2000 rev.2), SANCO/1344/2010, the Generic Guidance for Estimating Persistence and Degradation Kinetics from Environmental Fate Studies in Pesticides in EU Registration (version 1.1)and Guidance Document for evaluating laboratory and field dissipation studies to obtain DegT50 values of active substances of plant protection products and transformation products of these active substances in soil (Commission Guidance Document SANCO/12117/2014 – final).

Applicants will need to consider all the above reports in conjunction with each other to compile reports on groundwater exposure calculations submitted after 1st May 2015 and must include calculations using the latest versions of the models.  Please note whilst some crop interception values have changed, a geomean Kfoc / Kfom often needs to be used and under some circumstances as described, lab and field DegT50 values need to be amalgamated.  HSE will maintain a pragmatic approach for product authorisation submissions. See Summary of New Guidance.

NOTE HSE will NOT require Applicants to update soil DT50 values in line with the EFSA DegT50 guidance for plant protection product submissions, instead Applicants should continue to use Annex I agreed endpoints.  The same approach will apply to Koc values – Applicants should continue to use the Annex I agreed mean value, and not routinely use the geometric mean as proposed in the new guidance.

The other major change in this guidance is related to crop interception values for certain crops and growth stages; as the crop interception values relate to the use/GAP of the plant protection product and not to the properties of actives substances and/or metabolites, HSE will potentially apply the new crop interception values for submissions made from 1st May 2015. However, as far as possible HSE intends to make use of existing risk envelopes.

Active substance PECGW calculations (for EU, Zonal and UK specific authorisation requests)

The FOCUS groundwater models are run with nine realistic worst case scenarios when assessing potential active substance contamination of groundwater; collectively they represent agriculture across Europe.  However, for UK authorisations, 4 of these have been identified as being relevant to UK conditions: Châteaudun, Hamburg, Kremsmünster and Okehampton.  Other MS may use a selection of the 9 scenarios.  Therefore Applicants should consider which scenarios they model depending on whether the submission is addressing registration only in the UK or in a wider range of MS.

Additionally, for Zonal authorisations, Applicants are required to present simulations using MACRO 5.5.4 where the crops of interest are defined for the Châteaudun scenario.  However, an additional requirement for the UK is Applicants are required to present simulations using MACRO 5.5.4with the Châteaudun scenario to assess potential groundwater contamination for all active substances with a Koc>100 ml/g, using a suitably justified surrogate crop where the crop of interest has not been defined for the Châteaudun scenario.

Metabolite PECGW calculations (for EU, Zonal and UK specific authorisation requests)

Soil metabolites which may leach into groundwater must also be assessed using the FOCUS Groundwater scenarios and models as for the active substance.  Metabolites which are found to occur at significant levels (>0.1 µg/l) must also be considered for toxicological relevance in a stepwise approach according to the approaches in the 'Relevance of metabolites in groundwater, SANCO/221/2000 – rev.10, 25 February 2003', noting the maximum permitted level of relevant metabolites is also 0.1 µg/l.

It should be noted that the models require 'formation fractions' for metabolites when these are being modelled from degradation of the parent substance.  The formation fraction is the amount of substance converted to another substance, eg active substance to metabolite A, metabolite A to metabolite B, etc.  The formation fraction is distinct from the observed maximum amount (or formation percentage) of metabolite measured in a laboratory or field study and used in soil exposure calculations.

An additional requirement for the UK is Applicants are required to present simulations using MACRO 5.5.4with the Châteaudun scenario to assess potential groundwater contamination for all metabolites with a Koc>100 ml/g, using a suitably justified surrogate crop where the crop of interest has not been defined for the Châteaudun scenario, even where the parent Koc is not >100 ml/g.

Updated 2017-01-27