Estimating the Exposure of Birds and Mammals to Pesticides in Long-term Risk Assessments

Abstract

This paper reviews current EU pesticide risk assessment guidance [European Commission (2002) Guidance document on risk assessment for birds and mammals under council directive 91/414/EEC, SANCO/4145/2000EC 2002], and examines some of its assumptions and problems arising from them. Issues associated with obtaining data that adequately describes exposure over the appropriate time-scale are common to both acute and long-term risk assessments but are probably less problematic for long-term exposure. Improvements in problem formulation and ways in which temporal and spatial factors might be incorporated into long-term risk assessments are suggested. The most important temporal issue for long-term risk is how best to model the degree to which wildlife habits are predictable from day to day. In relation to spatial factors, it is suggested that long-term risk assessments could make better use of pesticide usage data that sample usage patterns throughout the UK. The usefulness of detailed simulated farming landscapes populated by wildlife represented as agent-based models, should be explored.

Case Study Part 1: How to Calculate Appropriate Deterministic Long-Term Toxicity to Exposure Ratios (TERs) for Birds and Mammals

“…The ETE is for generic insectivorous and herbivorous birds and mammals that have fixed default body weights and food intake rates ( Table 3). Calculation of the ETE is described in detail elsewhere (European Commission, 2002;Crocker, 2005). Default values (Table 3) are used for all exposure inputs other than application rate and the number of repeat applications of the pesticide.…”

“…This also has the advantage of explicitly aligning the exposure term to the specific toxicity endpoint. Phase-specific (Crocker, 2005) are all assumed to be equal to one (see text for details).…”

“…The next stage of the case studies was to calculate phase-specific TERs for the skylark and wood mouse, two species potentially at high risk of pesticide exposure in cereal fields in Britain. The ways in which the ETE component of the TER can be refined for particular species is discussed by Crocker (2005). Relevant ecological data for the skylark and the wood mouse are summarised by Roelofs et al (2005) and were used here to refine the ETE for compounds I and F, respectively.…”

“…Better methods for estimating exposure were outlined (Crocker, 2005) and a novel approach for assessing toxicity was proposed; appropriate NOELs were determined for key stages in the breeding cycle and the possible consequence of toxic impact at each stage were estimated . Ways of incorporating inter-species differences in toxicological response into the assessment were considered .…”

Improved Approaches to Assessing Long-term Risks to Birds and Mammals

“…Crocker (2005) examines some of the assumptions and problems arising from current EU pesticide risk assessment guidance in exposure assessment. Improvements in problem formulation and ways in which temporal and spatial factors might be incorporated into long-term risk assessments are suggested.…”