A New Interpretation of Avian and Mammalian Reproduction Toxicity Test Data in Ecological Risk Assessment

Abstract

The long-term risks of pesticides to wildlife in the EU currently are assessed by comparing the lowest no-observed-effect concentration (NOEC) determined from the suite of endpoints measured in existing avian and mammalian laboratory reproduction tests with estimated exposure concentrations by calculating Toxicity to Exposure Ratios (TERs). Regulatory authorities experience difficulties when assessing long-term risks because of the lack of accepted methods to improve the ecological realism of exposure and toxicity estimates and understand risks at a population level. This paper describes an approach for interpreting existing avian and mammalian toxicity test data that divides breeding cycles into several discrete phases and identifies specific test endpoints as indicators of direct pesticide effects possible at each phase. Based on the distribution of breeding initiation dates for a species of concern and the dates of pesticide applications, this approach compares the phase-specific toxicity endpoint with the expected pesticide exposure levels during each of the breeding phases. The fate of each breeding attempt is determined through a series of decision points. The cumulative reproductive response of individuals in a breeding population based on this decision framework provides a means of examining the estimated risks over the course of the breeding season and deriving an overall metric of the impact of the pesticide on reproduction. Research needed to further improve the approach is discussed.

Effects of agriculture expansion and intensification on the vertebrate and invertebrate diversity in the Pampas of Argentina

“…Those Pampean species associated with grassland remnants and linear undisturbed habitats were affected by the loss of sites for nesting and digging shelters (Hodara et al 1997;Gómez Villafañe et al 2005). Increased usage of pesticides indirectly damaged rodents by reducing food availability through depletion of invertebrate prey, vegetation cover and weed seeds (Zaccagnini and Calamari 2001;Bennett et al 2005).…”

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

“…In principle therefore, the effects assessment should be driven by exposure assessment not the other way round. Bennett et al (2005) show how existing laboratory longterm toxicity test endpoints may be linked to the time course and natural history of particular wildlife species at risk. Therefore, this paper does not settle on a particular duration for ''longterm'' but rather outlines a general model that will allow exposure to be estimated over the course of any term.…”

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

“…Therefore, there are still issues in using the data for ecological assessment of long-term impacts to wild mammal populations. Bennett et al (2005) take the data a step further in providing a new interpretation of avian and mammalian reproduction toxicity test data. They describe an approach that divides breeding cycles into several discrete phases and identifies specific toxicity test endpoints and the expected pesticide exposure levels for each of these breeding phases.…”

“…The first two case studies used the toxicity-exposure linking rules developed by Bennett et al (2005) and the interspecies extrapolation factors suggested by Luttik et al (2005). The first case study refined deterministic methods by calculating a TER for each of five identified phases of reproduction with progressive refinement of the exposure estimate so that it applied to the particular species, rather than generic indicators, and related spraying date to onset of reproduction.…”