Trifluoroacetate leaching potential from fluorinated pesticides: an emission estimation and FOCUS modelling approach

Abstract Background Trifluoroacetate (TFA) is a substance of rising concern, because TFA is widespread and high TFA levels have been detected in groundwater, causing an imminent threat, e.g. to organisms in groundwater. Potential precursors of TFA contain at least one carbon-bound trifluoromethyl moiety, which includes several pesticides. However, only for few pesticides empirical evidence for TFA formation is available. This paper aims to provide an estimation of TFA emissions from pesticides used in the EU by applying two approaches. The estimation approach was based on application and crop cultivation data and was used to calculate (a) the theoretical TFA formation in g/ha for typical pesticidal uses in the EU and (b) TFA formation in t by considering crop cultivation areas in the EU. In addition, a worst-case groundwater modelling approach was developed to assume the TFA leaching potential from particular pesticide applications with the model commonly used in pesticide regulation. For the FOCUS modelling approach, we used harmonised EU endpoints for physico-chemical parameters of pesticide active substances and added TFA as metabolite, considering a worst-case formation of 100% from precursors. Results The lowest TFA formation potential in g/ha was determined for insecticides, while fungicides showed a strong variation. Taking crop production areas into account, five herbicides were identified as the most important TFA sources. The modelled TFA concentrations in groundwater were above 10 µg/L for most substances except for insecticides which predominately range from 0.1 µg/L to 10 µg/L. This is far above the legal limit of 0.1 µg/L for relevant pesticide metabolites in groundwater. Considering the results of both approaches, we prioritised nine out of 24 active substances as the most crucial ones regarding TFA leaching in the EU: diflufenican, flonicamid, fluazifop-P-butyl, fluazinam, flufenacet, fluopyram, flutolanil, picolinafen and trifloxystrobin. Conclusions Our estimated TFA emissions indicated potentially unacceptable leaching of TFA into groundwater. The most important active substances identified here can be used as priority substances to address this topic. Overall, it becomes clear that improved regulatory assessment of TFA is necessary in pesticide risk assessment.