Pesticide terrestrial field dissipation (TFD) studies are conducted in North America and/or Europe to fulfill data requirements on persistence ,dissipation, degradation rates, formation and decline of transformation products, volatilization, plant uptake, leaching, etc in the field under actual use conditions. In the European regulatory framework the degradation rates (DegT50) from TFD studies are seen to be more realistic for exposure modeling than from laboratory studies and can originate from “any” site with similar soil and climatic conditions.  In an experimental and GIS/modeling feasibility study we investigated if TFD-studies conducted in the Southern hemisphere (i.e. New Zealand or Chile) Northern hemisphere may deliver similar endpoints (degradation rates in soil, DegT50) than those from from the Northern hemisphere (Europe or NAFTA region). An OECD Ecoregion similarity model was used for analysing the representativeness of field trials conducted in NAFTA vs. Europe and the Southern hemisphere. As the current ENASGIPS method only allows NAFTA/Europe comparisons we extended the concept to other regions using ArcGIS and available geodata from the 3 regions.  TFD trials were conducted according to OECD 232 (DegT50 module, bare soil covered with sand) with 3 different pesticides having moderate DegT50 at 3 sites in New Zealand and 3 sites in Chile, having no historic use of these pesticides. All pesticides were applied in commercial formulations as a tank mix together in the same spraying on the same field plots at the same time. The sites had soil types ranging from sands, loamy sands loams. In New Zealand the sites were located on the Northern Island having an average annual air temperature of ~ 12-13 °C and an average cumulative annual rainfall of ~ 780- 970 mm. In Chile the sites were located in the Región del Bío-Bío, east of Concepción having an average annual air temperature of ~ 14 °C and an average cumulative annual rainfall of ~ 800-900 mm.  The Field DegT50 for the 3 compounds in New Zealand and Chile are normalized to reference conditions (20 °C, moisture pF2) during kinetic analysis according to FOCUS kinetics, considering soil characteristics and actual local weather data. They are then compared with normalized DegT50 values of TFD studies with the same compounds in Europe. The normalized SFO DegT50 of all compounds in the “Southside” trials in New Zealand and in Chile as well as in Europe were found to be in the same range.

Ecoregion similarities of field trials– Comparison of field degradation data of some pesticides from New Zealand, Chile and Europe

256th National Meeting (2018)

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