Estimation of photochemical degradation rates of pesticides in outdoor cosm water : Guidance for inclusion in higher tier exposure assessments of the registration procedure in The Netherlands or at EU level, using the TOXSWA model

Abstract

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Higher-tier degradation rates in water for the regulatory aquatic risk assessment of pesticides

“…Two laboratory-scale water-sediment systems in the dark (OECD Guideline 308, 2002) are required to determine the (overall system) degradation rate of active ingredients for use in exposure models. To estimate more realistic degradation rates for the water layer in small surface waters a methodology was developed in a series of three reports: 'Water only' in Deneer et al (2015), 'Water-sediment' in Adriaanse et al (2017) and 'Photolysis dominant degradation process in water' in Adriaanse et al (2021). The methodology is based upon inverse modelling of the substance behaviour in outdoor cosms by the TOXSWA model, i.e.…”

“…The methodology in Deneer et al (2015) is suitable for outdoor cosm studies in which at least (i) five concentrations in water over time and (ii) the water depth have been measured, while for the methodology in Adriaanse et al (2017) in addition, at least (iii) three concentrations in sediment over time and (iv) the relevant sediment depth should have been measured. For outdoor cosms with substances having indications for susceptibility to photolysis in water, there should ideally be information on the actual incoming UV-VitD 1 radiation, the skyview factor and the coverage of the water surface area by macrophytes (Adriaanse et al, 2021).…”

“…Twee water-sediment studies, uitgevoerd in het donker in het laboratorium (OECD Richtlijn 308, 2002), zijn verplicht om de algehele systeem afbraaksnelheid van actieve stoffen te bepalen voor gebruik in de blootstellingsmodellen. Om meer realistische afbraaksnelheden in de waterlaag van kleine oppervlaktewateren te bepalen, is een methodiek ontwikkeld in een serie van drie rapporten: 'Water only' in Deneer et al (2015), 'Water-sediment' in Adriaanse et al (2017) en 'Photolysis dominant degradation process in water' in Adriaanse et al (2021). De methodiek is gebaseerd op het invers modelleren van het stofgedrag in een cosm in de buitenlucht door het model TOXSWA, terwijl de overeenkomst tussen gemeten en gesimuleerde concentraties wordt geoptimaliseerd door de waarde van de DegT50,water te variëren.…”

Guidance document on the impact of water treatment processes on residues of active substances or their metabolites in water abstracted for the production of drinking water

“…Worst‐case dilution factors to be applied: Central European Regulatory Zone: 2Dilution factors have been published for multiple countries within the Central European Regulatory Zone. For the Netherlands, dilution factors below 5 (De Greef and De Nijs, 1990) and 2 (Adriaanse et al., 2008) have been reported. For Germany, 5 has been reported (Link et al., 2017).…”

“…The Netherlands have been the first to implement emission reduction plans (ERPs), to address exceedance of the WFD thresholds. Another approach is public information, for which a set of 17 information sheets about measures to reduce the emission of pesticides to surface water is freely available online (Adriaanse et al., 2008; Mohaupt et al., 2020).…”