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Information Session on the EFSA Guidance on Predicting Environmental Concentrations in Soil: Issues Arising

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Information Session on the EFSA Guidance on Predicting Environmental Concentrations in Soil: Issues Arising

The European Food Safety Authority (EFSA) recently held an information session on the Guidance for predicting environmental concentrations (PECSOIL) of active substances of plant protection products and transformation products of these active substances in soil (EFSA, 2017) in Parma on 4 – 5 June, 2019. The session was aimed at providing stakeholders with an overview of the proposed new procedures for exposure assessment of in-field soil organisms in accordance with Regulation (EC) No. 1107/2009.

It is interesting to note that development of the current exposure assessment procedures for in-field soil organisms and guidance document dates back nearly ten years when EFSA published the first Scientific Opinion on outline proposals for the assessment of exposure of organisms to substances in soil (EFSA, 2010). Whilst the scientific approach appears to have been finalised, the computer based modelling tools required for implementation of the procedures in regulatory practice have yet to be made publicly available – partly because of the challenges of integrating the complexities of the new procedures in user-friendly software tools. Presenters at the information session specifically noted issues with the PERSAM transfer files, as well as the handling of row treatments by the numerical models PEARL and PELMO. PERSAM is expected to be finalised and made publicly available this September. Moreover, new updated versions of PEARL and PELMO are expected to be submitted to FOCUS Version Control in June-July, and it is anticipated that final versions of the numerical models will be made publicly available by the end of 2019.

Once the modelling tools for implementation of the new procedures in regulatory practice are publicly available, EFSA will notify the Commission and implementation of the exposure assessment framework for in-field soil organisms in accordance with the guidance document is expected to commence in about a year and half from now after a 6 months transitional period i.e. anticipated around the end of 2020.

Some important features of the new procedure as well as modelling tools which have not been explicitly addressed in the EFSA guidance document, but which were noted at the information session, and would no doubt be critical for Applicants planning for regulatory approval or renewal of their active substances and plant protection products in the coming years, include:

(i) The exposure assessment endpoint currently focuses on concentration in total soil at a depth of 5 cm, and will remain so until guidance on risk assessment of plant protection products for in-soil organisms have been finalised by EFSA. The calculated concentrations in pore water may, however, in the future find use as a surrogate for puddle concentration in the exposure assessment of birds, mammals and bees.

(ii) A new feature with PERSAM is the possibility to select and perform assessments for individual EU Member States at Tier 2 of the new procedures, and subsequently with PEARL and PELMO at Tier 3A. Additional features in PERSAM include: input tabs for time since last application (tpost-app) and RAC. PERSAM provides results in the form of numerical tables, PEC/RAC ratios and spatially distributed PEC values, RAC exceedance maps, and probability density functions for each regulatory zone or individual Member State assessment. This feature underlines the critical importance of spatially explicit datasets at lower tiers of the exposure assessment, and EU Member States are likely to ask for country-specific exposure assessments as part of the national addendum to the core dossier.

(iii) User defined crop maps can also be imported into PERSAM and used for the exposure assessments, subject of course to regulatory acceptance. Country-specific crop maps could be useful in this regard.

(iv) Product application rates can be based on: (a) the entire field, or (b) the area treated e.g. in-row or between-row treatment. But this information should be specified in the GAP by the Applicant. For non-standard application to annual crops e.g. row treatment or crops grown on ridges, a default value for the fraction of the treated field (ftreated) is only available for potatoes. For other crops, including permanent crops, Applicants would need to secure agreement with the Regulatory Authorities for an appropriate value of ftreated to use in their exposure assessments. And different Regulatory Authorities may suggest different values of ftreated, thus potentially complicating or duplicating assessments, especially at Zonal and Member State levels.

(v) Aged sorption can be considered at Tier 3A or 3B of the exposure assessment procedures. However, it is not certain what effect, if any, aged sorption would have on the endpoint concentration in total soil. On the other hand, aged sorption would be expected to be a significant factor for concentrations in pore water for substances that exhibit this behaviour. This may be an important higher tier refinement option for the future, when the pore water concentrations are used in regulatory risk assessment of in-field soil organisms.

(vi) For substances with pH-dependent properties, a pH-dependent relationship must be defined in the PERSAM model. The implication of this is that Applicants must have sufficient dataset which, for many active substances and transformation products, is not the case. The current approach for groundwater (i.e. two simulations, one each at acidic and alkaline Koc or DegT50) is not applicable for in-field soil exposure assessment because of the process for selection of scenario locations in PERSAM. So there is likely to be additional cost implications for Applicants in order to generate required endpoints for those active substances and transformation products that exhibit pH-dependent properties.         

The EFSA information session did not address several other aspects of the new procedures and guidance critical for exposure assessment of in-field soil organisms. For example, there is some uncertainty as to the approach Member State Competent Authorities would apply in evaluating non-uniform applications in annual and perennial crops, besides crops grown on ridges e.g. potatoes. More information or clarity is needed on uses of the rapidly dissipating fraction derived from field dissipation studies (fFIELD) in the refinement of exposure concentrations at higher tiers. Lastly, there appears to be no immediate use for Tier 3B of the procedures or spatially distributed modelling with numerical models – as other modelling tools and databases are not supported by EFSA for EU regulatory purposes – only PERSAM, PEARL, PELMO and the EFSA spatial datasets are currently supported.

You can find the new EFSA soil guidance document here: https://www.efsa.europa.eu/en/efsajournal/pub/4982

You can view the presentations that were made at the EFSA information session here: https://www.efsa.europa.eu/en/events/event/190604

If you would like to discuss any of the issues raised in this article further, please contact Abdul Abu (Abdul.abu@cea-res.co.uk). 

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