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Development & validation of exposure models for non-oral pesticide uptake - PS2325

EU Directive 94/414 requires that plant protection products have no unacceptable effects on the environment particularly non-target species. Defra Pesticides Safety Directorate (PSD) is responsible for assessing the environmental safety of pesticides in the UK. Currently risk assessments for birds and mammals assume, in the absence of other data, that dietary intake is the primary route of exposure. Several published studies have highlighted the potential for dermal and other non-dietary routes of exposure to increase the risk to birds during or after pesticide applications. While information on non-dietary exposure of birds is not required in the current Guidance Document on Risk Assessment for Birds and Mammals, development of models to deal with this has been identified as a research need - ‘this is a serious gap and all efforts should be made to develop models in the near future.’ The lack of appropriate methodology has been the limiting factor in determining how important other routes of exposure may be when assessing the risks to birds posed by current UK agricultural practices. However, PSD-funded Project PS2309 ‘Non dietary routes of pesticide exposure in birds’ began the process of developing a test scenario, for UK-relevant crops (oilseed rape) and bird species (pigeon), from which quantitative exposure and toxicity assessments for non-oral routes of exposure to a model compound (chlorpyrifos) could be made. This semi-field assay compared the exposure effects of birds that had unrestricted access to ‘freshly-sprayed’ plants (all exposure routes) with those whose access was restricted by a mesh barrier, so that only their beak came into contact with the plant (oral-only exposure route). Differences in toxicity endpoints between treatment groups (i.e. sub-lethal effects and symptoms) provided an estimate of the ‘non-oral exposure routes’ contribution to the pesticide’s total exposure estimate. There were two key issues which allowed the test system to be considered effective 1. birds in the restricted-access group had minimal or no non-oral contact with the plants and 2. the feeding rates in both treatment groups were similar. The results of this pilot study showed that ‘all routes’ of exposure made a greater contribution over time to a reduction in serum butyryl-cholinesterase activity (a marker of exposure) than the ‘oral only’ group. This could be due to the birds receiving a chronic dose through gradual dermal absorption compared with a short term oral exposure. This project will further develop and test the methodology with the aim of quantifying the extent of any increased risk that it presents to birds by investigating the potential for exposure by these routes, in conditions relevant to the UK and with a range of active ingredients and formulations. The results will assist PSD by providing better information about the potential importance of such exposure and identify what further research is necessary to confirm the importance of non-dietary routes of exposure, e.g. species with differing foraging behaviour, and appropriate methods for its assessment. The results of this, and any further work leading from it, will lead to improved risk assessment procedures by taking into account all significant routes of exposure and hence reduce the risk to wildlife from pesticide use.
1)Validation of ‘pigeon/oilseed rape’ exposure scenario to provide improved total exposure estimates for herbivorous birds. (28.02.07).

2)Determine the level of increased exposure due to non-food routes of exposure in birds foraging under relevant conditions for the UK for the chosen active substances (28.02.07).

3)Establish the potential for using biomarkers as a means of detecting toxic effects from the use of pesticides classed as pyrethroids or neonicotinoids (28.2.07).

Project Documents
• Final Report : Development & validation of exposure models for non-dietary pesticide uptake   (4399k)
Time-Scale and Cost
From: 2005

To: 2007

Cost: £124,176
Contractor / Funded Organisations
Central Science Laboratory
Environmental Effects              
Pest and Weed Control              
Pesticide use              
Plants and Animals              
Fields of Study
Pesticide Safety