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

Abstract

In the European Union, first-tier assessment of the long-term risk to birds and mammals from pesticides is based on calculation of a deterministic long-term toxicity/exposure ratio (TER(lt)). The ratio is developed from generic herbivores and insectivores and applied to all species. This paper describes two case studies that implement proposed improvements to the way long-term risk is assessed. These refined methods require calculation of a TER for each of five identified phases of reproduction (phase-specific TERs) and use of adjusted No Observed Effect Levels (NOELs) to incorporate variation in species sensitivity to pesticides. They also involve progressive refinement of the exposure estimate so that it applies to particular species, rather than generic indicators, and relates spraying date to onset of reproduction. The effect of using these new methods on the assessment of risk is described. Each refinement did not necessarily alter the calculated TER value in a way that was either predictable or consistent across both case studies. However, use of adjusted NOELs always reduced TERs, and relating spraying date to onset of reproduction increased most phase-specific TERs. The case studies suggested that the current first-tier TER(lt )assessment may underestimate risk in some circumstances and that phase-specific assessments can help identify appropriate risk-reduction measures. The way in which deterministic phase-specific assessments can currently be implemented to enhance first-tier assessment is outlined.

Risk Assessment for Birds and Mammals ‐ Revision of Guidance Document under Council Directive 91/414/EEC (SANCO/4145/2000 – final of 25 September 2002) ‐ Scientific Opinion of the Panel on Plant protection products and their Residues (PPR) on the Science behind the Guidance Document on Risk Assessment for birds and mammals

“…Full details regarding these four phases are provided in a PPR opinion (EFSA, 2006) and Bennett et al (2005), as well as Appendix 16.…”

“…Unfortunately, there are no population models that can be readily used or adapted for use in pesticide risk assessment. Existing possible examples of population models are presented in Topping et al (2005), Sibly et al (2005) and . It should be noted that the models included in these references are not endorsed but are provided as an indication of the types of studies that are available.…”

“…Other influential factors include the number of food types considered and whether these are the same in each part of the landscape. Crocker (2005) shows how the assumptions made can influence the form of dietary exposure model required. However, it must be noted that the equations presented by Crocker (2005) include a factor to represent avoidance, although Crocker identifies several problems with this in his text.…”

“…Crocker (2005) shows how the assumptions made can influence the form of dietary exposure model required. However, it must be noted that the equations presented by Crocker (2005) include a factor to represent avoidance, although Crocker identifies several problems with this in his text. EFSA (2004, 2005a) has concluded that including avoidance in exposure modelling in this way (at least for substances where avoidance is determined by a threshold dose, rather than by a concentration-related sensory response) is not appropriate.…”

“…Note that a 1-d delay may be of importance for certain substances. It should be checked that this is not treatment related before discounting it.Full details regarding these four phases are provided in a PPR opinion (EFSA, 2006) and Bennett et al (2005), as well as Appendix 16.The mammalian toxicology data package needs to be consulted, in particular the multigeneration reproductive toxicity study, the developmental toxicity studies, the oral LD 50 …”