Shortcomings of the European Regulatory Pesticide Risk Assessment for Surface Waters
Anja Knäbel, Sebastian Stehle
Presentation: 28.10.2013, 10:45 am [Video]
Discussion: 28.10.2013, 11:00 am [Discussion]
Pesticides are highly biological active substances that are applied to the environment deliberately. Subsequent to their entry in aquatic environments they pose a substantial threat to the ecological integrity of surface water systems as they exhibit a high toxicity potential towards a wide range of aquatic organisms. Indirect effects and biomagnification can influence higher trophic levels and in consequence also pose a threat to human health. Elaborate regulatory and legally manifested environmental risk assessment procedures have been enforced in the European Union in order to control risks associated with pesticide use. Within the European pesticide registration procedure, a tiered exposure and effect assessment is conducted to prevent unacceptable ecological effects of pesticides for terrestrial and aquatic non-target organisms in the environment.
The regulatory exposure assessment for aquatic ecosystems is conducted using exposure models as the compounds under assessment are not yet available on the market and in use. The FOCUS modeling approach is used to determine the predicted environmental concentration (PEC) in surface water and sediment and is intended to reflect the exposure levels of specific pesticide compounds under (realistic) worst-case conditions. The FOCUS modeling approach consists of four different tiers for which the degree of conservatism decreases and the degree of realism increases from tier 1 to tier 4. In parallel, aquatic effect data are derived from very conservative acute and chronic laboratory tests using large safety factors (first tier; conservative & less realistic) and higher tier effect assessments using semi-field model ecosystem experiments (micro- or mesocosms) and no or only very small safety factors (higer tier assessment; less conservative but very realistic). The modelled PECs (including specific risk mitigation measures, e.g., no-spray buffer zones) must be smaller than the measured effect data including safety factors (=Regulatory Acceptable Concentrations (RAC)) in order to indicate an acceptable environmental risk for aquatic ecosystems in the field. Otherwise, no registration can be granted.
In the field, actual pesticide concentrations detected in agricultural surface waters are above PECs and RACs, indicating environmental risks for aquatic ecosystems and regulatory risk assessment failures. Potential reasons are the failure of the exposure assessment (FOCUS models) or farmers adherence to risk mitigation/management prescriptions. In conclusion, uncertainties associated with environmental risk assessment for pesticides may influence the health for environment, animals and people.
The regulatory exposure assessment for aquatic ecosystems is conducted using exposure models as the compounds under assessment are not yet available on the market and in use. The FOCUS modeling approach is used to determine the predicted environmental concentration (PEC) in surface water and sediment and is intended to reflect the exposure levels of specific pesticide compounds under (realistic) worst-case conditions. The FOCUS modeling approach consists of four different tiers for which the degree of conservatism decreases and the degree of realism increases from tier 1 to tier 4. In parallel, aquatic effect data are derived from very conservative acute and chronic laboratory tests using large safety factors (first tier; conservative & less realistic) and higher tier effect assessments using semi-field model ecosystem experiments (micro- or mesocosms) and no or only very small safety factors (higer tier assessment; less conservative but very realistic). The modelled PECs (including specific risk mitigation measures, e.g., no-spray buffer zones) must be smaller than the measured effect data including safety factors (=Regulatory Acceptable Concentrations (RAC)) in order to indicate an acceptable environmental risk for aquatic ecosystems in the field. Otherwise, no registration can be granted.
In the field, actual pesticide concentrations detected in agricultural surface waters are above PECs and RACs, indicating environmental risks for aquatic ecosystems and regulatory risk assessment failures. Potential reasons are the failure of the exposure assessment (FOCUS models) or farmers adherence to risk mitigation/management prescriptions. In conclusion, uncertainties associated with environmental risk assessment for pesticides may influence the health for environment, animals and people.
