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10th European Modelling Workshop Highlights

At the end of August, Sabine Beulke and Emma Tilston were invited to attend the 10th European Modelling Workshop at York. The workshop provides a unique forum for representatives of pesticide producing companies, competent authorities and environmental fate risk assessors to learn about forthcoming improvements to the existing regulatory framework, work in progress and to propose where further improvement is needed.

EFSA activities

Gabriella Fait, from the EFSA Chemistry and Environmental Exposure team had much to report. In the coming months we can expect the following:

  • Guidance on soil photodegradates in groundwater (October 2022)
  • Finalisation of the revised guidance and on-line calculator tool on the risk assessment for birds and mammals, which includes a proposal for surrogate crops for crop interception, tier 1 secondary poisoning assessments and pore water PEC in the top 1 cm of soil as surrogate for PECpuddle (December 2022)
  • A statement on the design and conduct of groundwater monitoring studies supporting groundwater exposure assessments of pesticides (March 2023)
  • Guidance on the impact of drinking water treatment processes on residues of substances in water abstracted for use as drinking water (June 2023)
  • Consultation regarding the temporal exposure assessment goal (percentile year) to be used in the aquatic risk assessment now that PECsw is based on 20 assessment years not 16 months as a result of FOCUS surface water ‘repair’ (pending).
  • The adoption of the new PECsoil software tools PERSAM, PEARL and PELMO and EFSA (2017) PECsoil guidance (also pending)

Testing of the new suite of FOCUS tools for PECsw assessments released in February 2022 was paused in June 2022, so until those issues are resolved further development of a new modelling package for the calculation of PECsw under FOCUSsw ‘repair’ is on hold.

UBA guidance on pH dependency of pesticide sorption or degradation

Representatives of UBA, the German Environment Agency presented an update on their progress with developing guidance on how to identify possible pH-dependency of degradation and/or adsorption in soil and how to select suitable endpoints for active substances and metabolites when calculating PECgw. Their work aims to integrate EFSA guidance with Dutch and German national guidance and common approaches used on an individual basis during EU approval. Draft guidance and a software tool for a standardised step-wise procedure for EU approval and zonal registration are currently being revised. A second stakeholder consultation is planned for 2023 and will include extension of the guidance for PECsw/PECsed and PECsoil. After discussion in a PPR meeting organised by EFSA, the plan is to publish the guidance as an EFSA technical report. Based on their progress so far, their efforts are anticipated to make assessing the environmental risk of substances with pH dependencies much easier.

Revision of the Dutch leaching assessment

The Netherlands Environmental Assessment Agency gave a presentation about using GeoPEARL v4.4.4 for national assessments of leaching risk. GeoPEARL is a spatially distributed model used at Tier 2 for the explicit evaluation of the leaching potential in the area in which a plant protection product is planned to be used in the Netherlands. In 2010, it was noted that the crop area data were many years out of date and soil profile information from both arable and grassland soils had been used to generate the values for soil organic matter in the GeoPEARL database. Thus, the soil organic matter content of arable soils was over-estimated by GeoPEARL with the result that leaching to groundwater was being underestimated. Although the release of GeoPEARL v4.4.4 in 2018 addressed the database deficiencies of v3.3.3, there was a 2- to 10-fold increase in predicted leaching concentrations between the old and new model versions. This difference confounded the tiered approach of the Dutch decision tree on leaching with Tier 2 GeoPEARL simulations predicting larger concentrations than the Tier 1 simulations for the Kremsmünster scenario in the FOCUSPEARL model. To avoid this inconsistency, a calibration factor of 5 to 10 at Tier 1 has been proposed.


At a time when the environmental risk assessment framework has arguably fallen out of step with scientific knowledge and new policy directions concerning the environment, agriculture and the use of chemicals both inside and outside the EU, issues like those affecting GeoPEARL v3.3.3. are likely to emerge for other calculator tools. The challenge for coming years will be to address pre-existing issues, and to develop frameworks and tools that enable greater linkage of environmental exposure with ecotoxicology. With increasingly diverse agricultural and horticultural sectors and the current rate of technological and policy change, it is evident that it is becoming increasingly difficult to define what is an acceptable level of protection and what a relevant regulatory framework should look like. The next workshop is only 2-years away, but already the programme is likely to be very full and to provoke just as much discussion.


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