A small application developed in R for the estimation of the residue intake rate for certain bee species under given conditions: the SHVAL tool

The risk to bees via consumption of nectar and pollen in the hive is assessed using parallel tiered approaches for the effect and exposure assessments both for spray applications, seed treatment and granule applications. The exposure assessment is based on tiered approaches described by flow charts (EFSA, 2013).The aim of the exposure assessment is to provide input into the assessment of the daily residue intake rate of the bees. This Residue Intake rate (RI) is expressed in μg/day. RI is calculated considering PECpollen and PECnectar as the “predicted environmental concentrations” (mg/kg) in pollen and nectar, and Cpollen and Cnectar as the consumption rates of pollen and nectar of a bee species (mg/day) (for more information about the underpinning equations see EFSA, 2014).The consumption rate of nectar is assessed as the quotient of the intake rate of sugar of a bee species (ds in mg/day) and the sugar content of the nectar (ms in kg/kg) defined as mass of sugar divided by mass of nectar.The concentrations in nectar and pollen are based on the concept of the Residue Unit Dose (RUD) which is defined as the residue (mg/kg) at a dose of 1 kg/ha. So usually the approach is to calculate the PEC as a function of the RUD and the δ which is the dose (kg/ha).Concentrations in plants other than the treated crop should also be assessed (e.g. plants in field margins). In such cases, the approached as described above does not apply because only a fraction of the dose will be deposited on this field margin. Therefore a generalisation is needed including fdep, which is the fraction of the dose deposited on the plant.In the lower tiers of the exposure values, so-called shortcut values (SVs) are used. SV is the daily residue intake rate of a bee species (g/day) for a deposition of 1 kg/ha.Please note that different values of Cpollen, ds and ms have to be used when calculating the residue intake rates for the different bees, as explained in the EFSA Guidance (2013).For some of the bee species included in the evaluation, cumulative values of the RI over periods of 5 and 30 days are needed and then SV was also calculated over 5 and 30 days.In case measurements are available for the decline over time of the RUD values, it is possible to assess the Time-Weighted Average (TWA) residue intake rate as a function of the RUDpollen,0 (the RUDpollen at time zero), RUDnectar,0 (the RUDnectar at time zero), kpollen (the first-order rate coefficient (d-1) for the decline of the concentration in pollen), knectar (the first-order rate coefficient (d-1) for the decline of the concentration in the nectar), and t (the time period (number of days) over which the TWA is calculated)