Higher‐tier laboratory methods for assessing the aquatic toxicity of pesticides

Abstract

Registration schemes for plant-protection products require applicants to assess the potential ecological risk of their products using a tiered approach. Standard aquatic ecotoxicity tests are used at lower tiers and clearly defined methodologies are available for assessing the potential environmental risks. Safety factors are incorporated into the assessment process to account for the uncertainties associated with the use of lower-tier single-species ecotoxicity studies. If lower-tier assessments indicate that a substance may pose a risk to the environment, impacts can be assessed using more environmentally realistic conditions through the use of either pond mesocosms, artificial streams or field monitoring studies. Whilst these approaches provide more realistic assessments, the results are difficult to interpret and extrapolation to other systems is problematic. Recently it has been recognised that laboratory approaches that are intermediate between standard aquatic toxicity tests and field/mesocosm studies may provide useful data and help reduce the uncertainties associated with standard single-species tests. However, limited guidance is available on what tests are available and how they can be incorporated into the risk-assessment process. This paper reviews a number of these higher-tier laboratory techniques, including modified exposure studies, species sensitivity studies, population studies and tests with sensitive life stages. Recommendations are provided on how the approaches can be incorporated into the risk-assessment process.

A useful new insecticide bioassay using first-instar larvae of a net-spinning caddisfly, Cheumatopsyche brevilineata (Trichoptera: Hydropsychidae)

“…In particular, the caddisfly will be valuable for assessing the ecological impacts of chemicals such as nAChR agonists/antagonists, whose impact on aquatic invertebrates is prone to underestimation by the daphnid bioassay. Boxall et al 40) noted that laboratory bioassays using additional test species can provide important information for constructing species-sensitivity distributions in probabilistic risk assessments, which have drawn increasing attention recently. 41) This new bioassay can be for probabilis- 24) A. aegypti, 24) C. vidua, 22) I. dentifera, 22) C. seurati 22) , C. sphaericus, 22) and Artemia sp.…”

Sensitivity difference to insecticides of a riverine caddisfly, Cheumatopsyche brevilineata (Trichoptera: Hydropsychidae), depending on the larval stages and strains

“…1) Partial life-cycle tests will be useful tools for assessing the impact of chemicals on populations of aquatic organisms with a long life-span if these tests can be incorporated into a population dynamics model 1,29) In our laboratory culture of C. brevilineata, it took about 3 or more months to complete a life cycle. Thus, the full life-cycle toxicity test using this species will be complicated and require considerable time and effort to accomplish.…”

“…Acute toxicity tests performed at the most sensitive life stage possibly overestimate the effects of chemicals on populations. 1) A series of acute toxicity tests performed at different life stages can be useful to determine the profile of sensitivity in a life cycle, and to appropriately assess populationlevel effects on aquatic organisms.…”

Optimization of River Water Quality Surveys by Multivariate Analysis of Physicochemical, Bacteriological and Ecotoxicological Data

“…Chlorella vulgaris) organisms in inhibition tests provides a suitable evaluation of ecotoxicity. Simple multispecies laboratory studies not only could be beneficial in the risk assessment process, but are most appropriate when a substance impacts a known key species within a food chain (Boxall et al 2002;Selck et al 2002).…”