Scientific Opinion about the Guidance of the Chemical Regulation Directorate (UK) on how aged sorption studies for pesticides should be conducted, analysed and used in regulatory assessments

Aged sorption is the tendency of pesticides to adsorp more strongly with increasing time. As a results, it reduces the leaching of pesticides into groundwater. This opinion reviewes how aged sorption experiments can be included in the groundwater risk assessment.

The EFSA Panel on Plant Protection Products and their Residues reviewed the guidance on how aged sorption studies for pesticides should be conducted, analysed and used in regulatory assessment. The inclusion of aged sorption is a higher tier in the groundwater leaching assessment. The Panel based its review on a test with three substances taken from a data set provided by the European Crop Protection Association. Particular points of attention were the quality of the data provided, the proposed fitting procedure of aged sorption experiments and the proposed method for combining results obtained from aged sorption studies and lower‐tier studies on degradation and adsorption. Aged sorption was a relevant process in all cases studied. The test revealed that the guidance could generally be well applied and resulted in robust and plausible results. The Panel considers the guidance suitable for use in the groundwater leaching assessment after the recommendations in this Scientific Opinion have been implemented, with the exception of the use of field data to derive aged sorption parameters. The Panel noted that the draft guidance could only be used by experienced users because there is no software tool that fully supports the work flow in the guidance document. It is therefore recommended that a user‐friendly software tool be developed. Aged sorption lowered the predicted concentration in groundwater. However, because aged sorption experiments may be conducted in different soils than lower‐tier degradation and adsorption experiments, it cannot be guaranteed that the higher tier predicts lower concentrations than the lower tier, while lower tiers should be more conservative than higher tiers. To mitigate this problem, the Panel recommends using all available higher‐ and lower‐tier data in the leaching assessment. The Panel further recommends that aged sorption parameters for metabolites be derived only from metabolite‐dosed studies. The formation fraction can be derived from parent‐dosed degradation studies, provided that the parent and metabolite are fitted with the best‐fit model, which is the double first‐order in parallel model in the case of aged sorption.

Authors

PBL Authors
Aaldrik Tiktak
Other authors
Colin Ockleford
Antonio F Hernandez‐Jerez
Susanne Hougaard Bennekou
Michael Klein
Paulien Adriaanse
Philippe Berny
Theodorus Brock
Sabine Duquesne
Sandro Grilli
Thomas Kuhl
Ryszard Laskowski
Kyriaki Macherai
Olavi Pelkonen
Silvia Pieper
Michael Stemmer
Ingvar Sundh
Ivana Teodorovic
Chris J Topping
Gerrit Wolterink
Robert H Smith
Anne Louise Gimsing
Roy Kasteel
Arnaud Boivin
Ton van der Linden
Jose Oriol Magrans
Mark Egsmose

Specifications

Publication title
Scientific Opinion about the Guidance of the Chemical Regulation Directorate (UK) on how aged sorption studies for pesticides should be conducted, analysed and used in regulatory assessments
Publication date
27 August 2018
Publication type
Article
Page count
86
Publication language
English
Magazine
EFSA Journal
ISSN
1831-4732
Issue
16 (8)
Product number
4632