Pesticide risk assessment for birds and mammals
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4.5InterceptionThe residue unit doses (RUDs) for vegetation, as described in section 4.3, are derived from trials in which the plants are directly oversprayed. However, there will often be situations where particular food items for birds and mammals have lower concentrations due to the compound being partly intercepted by the crop before it reaches the food item. It may therefore be appropriate to include an interception factor (or rather its complement, a deposition factor) in the estimation of residues and the Daily Dietary Dose. Interception by the crop shall be considered as a minimizing factor for residues on plant food items and other food items exposed on or near the ground when canopy-directed applications of insecticides and fungicides to orchards, vineyards etc. are performed and undergrowth vegetation (assumed to be mainly grass) is present. Conversely, no interception factor shall be applied for herbicide applications in those crops, since these are typically made directly to the undergrowth vegetation. In field crops, the crop itself may be assumed to receive the full application rate. However, other plants will usually also be available as food. At certain stages the crop intercepts some of the applied product and hence the amount of pesticide deposited on food items below the crop will be less than the application rate. Since measured residues of such food items at the appropriate growth stage of the crop are not available, only estimates can be used. Estimates of the deposition on the soil surface below crops of different structure and growth stages are available in the FOCUS reports (FOCUS 2000, 2001). However, deposition on 3-dimensional structures (e.g. weeds) above the ground is probably different from the deposition on the 2-dimensional soil surface. According to EFSA (2009) estimation of residues on undergrowth vegetation using FOCUS interception factors becomes increasingly uncertain with decreasing soil cover of the crop and increasing height of weeds. Thus, reliable predictions are only deemed possible where the largest part of the soil surface is actually covered by the crop and the undergrowth vegetation is clearly smaller than the crop plants. Based on this assessment, EFSA (2009) concludes that the crop interception values used in the FOCUS surface water report (FOCUS 2001) for Step 2 PECSW calculations can be considered acceptable also in the context of bird and mammal risk assessment, provided that the growth stage is sufficiently advanced. These figures are likely to be conservative estimates and are thus mainly suitable for tier 1 assessments. It is therefore considered (EFSA 2009) that in the context of a higher tier assessment, the more detailed values of the FOCUS groundwater report (FOCUS 2000) may also be used (Table 4.2 and Table 4.). In higher tier risk assessment for birds and mammals within the Northern Zone the following approach is used4:
Table 4.2Interception (percent) at different combinations of crop and growth stage according to FOCUS groundwater. Only crops which are relevant for the scenarios considered in the present report are included in the table. Source: FOCUS 2000.
* An interception value of 90 % may be used for applications to established turf. ** BBCH code of 20-29 for tillering and 30-39 for elongation. Table 4.3 Interception (percent) by fruit trees (apples), bush berries and vines at different growth stages according to FOCUS groundwater. Source: FOCUS 2000.
It should be noticed that the FOCUS groundwater values are intended to be realistic (as opposed to conservative) estimates of the amount of pesticide that actually reaches the soil surface. Using these values may therefore lead to a (probably slight) underestimation of residues in weeds and other bird and mammal food items below the crop plants. Directory: media media -> Applications to Drill media -> Unicef voices of Youth Chat Theme: Children and aids nigeria and Zimbabwe 13 October 2006 Background media -> Tsunami Terror Alert: Voices of Youth media -> Biblical Eschatology Presentation by: D. Paul Beck May 4, 2016 Ground Rules media -> Guide to completing the collection using the Omnibus system media -> The milk carton kids media -> Events Date and Location media -> The Gilded Age: The First Generation of Historians by H. Wayne Morgan University of Oklahoma, April 18, 1997 media -> Analysis of Law in the United Kingdom pertaining to Cross-Border Disaster Relief Prepared by: For the 30 June 2010 Foreword media -> Cuba fieldcourse 2010 Download 2.61 Mb. Share with your friends:
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