Scientific Opinion on the science behind the guidance for scenario selection and scenario parameterisation for predicting environmental concentrations of plant protection products in soil

Based on consultation with Member States, EFSA asked the Panel to prepare a revision of the Guidance Document on the persistence of plant protection products in soil (SANCO/9188VI/1997 of 12 July 2000) as scientific knowledge in this field has evolved in recent years. Therefore the Panel developed a revised methodology for the assessment of exposure of soil organisms to such products. Based on a previous Opinion of the Panel, this methodology has been developed both for the concentration in total soil and the concentration in the soil pore water. The goal of the exposure assessment has been chosen to be the 90^th percentile of the exposure concentration in the intended area of use in each of the three regulatory geographical zones (North, Centre, South). The exposure-assessment methodology is restricted to spray applications to annual crops under conventional or reduced tillage (excluding tillage systems with ridges and furrows). The Panel proposes a tiered approach. Tier 1 is based on a simple analytical model. Tier 2A is based on simulations with numerical models. To keep the approach as simple as possible, the Panel based Tiers 1 and 2A for each regulatory zone on only one scenario each for the concentration in total soil and for that in pore water. These scenarios are to be used for all these annual crops and for all plant protection products in each regulatory zone. Tiers 2B and 2C are also based on the simple analytical model but in these tiers a specific crop or crop group and an individual plant protection product are considered. Tier 3 is based on simulations with numerical models but, as in Tiers 2B and 2C, a specific crop or crop group and a specific plant protection product are considered. All tiers aim to assess the same exposure assessment goal. Given the complexity of the calculations in the different tiers, efficient use of this tiered approach in the regulatory process is impossible without software tools. Therefore the Panel recommends developing user-friendly software tools for the calculation of the exposure concentrations in the different tiers.