The Phytopharmaceuticals section of the European Commission (EC) Standing Committee on Plants, Animals, Food and Feed (PAFF), which plays a key role in ensuring that Union measures on food and feed safety, animal health & welfare as well as plant health are practical and effective, noted and endorsed the ‘Guidance document on aged sorption’ at the meeting on 25-26 January under Fate & behaviour. It was further agreed that this guidance will be applicable from 1st April 2021 to dossiers submitted under Regulation (EC) no 1107/2009.
Together with collaborators, Enviresearch/Fera have been working with the Chemicals Regulation Directorate (CRD) for over 10 years developing and revising the new guidance for Aged Sorption. This development has included the design of the appropriate experimental protocol, standardisation of deriving the required parameters from the experimental data and how the parameters are subsequently used during exposure modelling.
Fera and Enviresearch have extensive experience in providing the best regulatory and risk assessment services in Europe for the global chemical industry, with a highly dedicated and experienced group of experts who are at the cutting edge of science underpinned with the power of Fera's experimental excellence.
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Chris is an expert in regulatory environmental risk assessment processes, registration requirements and guidance for pharmaceuticals, veterinary medicines and pesticides. Chris ensures delivery of the regulatory environmental risk assessment processes (quantifying risk for pesticides, veterinary medicines and feed additives) of environmental fate and behaviour of chemicals (e.g. movement of chemicals through soils to surface and ground waters) for our customers
Wendy is an environmental fate consultant at Enviresearch, with more than 15 years’ experience in pesticide fate processes and modelling. Wendy has applied and developed modelling and experimental techniques in a range of areas such as sorption and diffusion in soil and pesticide leaching. Wendy has contributed to the development of the aged sorption guidance and other procedures for regulatory risk assessment on behalf of the UK Chemical Regulations Directorate and EFSA.
Sabine is an Environmental Risk Assessor / Modelling Expert for Enviresearch and her role is to assess the environmental fate and effects of pesticides to support regulatory active substance renewals and product registrations in the EU. Sabine's particular interests include chemical-soil interactions, movement of chemicals into surface water and groundwater via drainage, runoff and leaching, and mathematical modelling, applying this expertise to the development of customised solutions to regulatory problems.
Aged sorption is measured in a laboratory study on a minimum of four soils. The aged sorption parameters (two parameters that describe the increase in sorption) are derived and the mean values are used in the standard FOCUS models (PEARL or PELMO) to refine the groundwater concentrations. The models then describe the increase in sorption strength over the year following application.
This reduces the availability for leaching to groundwater, resulting in reduced Predicted Environmental Concentrations (PEC).
Sorption of chemicals onto soil tends to increase with time, beyond the equilibrium sorption measured in standard OECD106 batch sorption studies. Backed up by good evidence, the effect of aged sorption may be accounted for in the risk assessment for groundwater at the higher tier.
An aged sorption study is performed as an incubation study equivalent to OECD guideline 307, but with an additional extraction step using 0.01 M CaCl2-solution. The data could therefore be obtained during the standard degradation studies with little extra effort. However, the guidance requires that the standard equilibrium sorption studies are also performed on the same soils, so it makes sense to plan ahead.
Aged sorption parameters are derived by fitting the Aged Sorption model, for example in PEARLNEQ. The guidance explains how to combine the aged sorption parameters with sorption and degradation endpoints from Tier 1 for the groundwater assessment.
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