Overview and rationale for developing regulatory guidelines for nontarget plant testing with chemical pesticides

Abstract

In the assessment of ecological risk posed by pesticide use, much greater emphasis has been given to the direct effects on wildlife than on impacts on wildlife habitat. Assessment of indirect effects to wildlife entails an evaluation of pesticide toxicity to plant species (and invertebrates) that make up wildlife habitats. Under the pesticide registration process in Canada and in most other countries, there is no specific requirement for testing the toxicity of pesticides to nontarget plants other than agronomically important species. The proposed nontarget plant testing guidelines summarized in this paper are intended to fill this gap. The chief objectives of the guidelines are to outline data requirements, to suggest methods and approaches for generating the data required, and to facilitate and improve hazard assessment for nontarget plants (and habitats) as a result of chemical pesticide use. The rationale behind decisions reached in the guidelines is also presented. The proposed guidelines are very flexible, as registrants may be granted a waiver for any test required, provided the rationale is justified on appropriate scientific grounds. Harmonization and comparison with other guidelines are discussed. These proposed nontarget plant testing guidelines can serve as a basis for guideline development or modernization for other jurisdictions.

Sublethal effects of atrazine on embryo-larval development of Rhinella arenarum (Anura: Bufonidae)

“…This percentage depends on exposure via spray drift, runoff, and washoff (10 %) or overspray exposure during aerial application (100 %). The EEC was calculated assuming a water depth of 15 cm and an area of 1 m 2 (Boutin et al 1993(Boutin et al , 1995. HQ is the ratio of the potential exposure to the substance and the level at which no adverse effects are expected (USEPA 1998), in this study was calculated as EEC/EC 10.…”

“…Ecological risk can be estimated numerically using the Hazard Quotient (HQ) approach (USEPA 1998), based on the comparison of the expected environmental concentration (EEC) (Boutin et al 1993(Boutin et al , 1995 with standard toxicity end points (e.g., EC 10 values). Toxicity bioassays, e.g., FETAX (Morgan et al 1996) and AMPHITOX (Herkovits and Pérez-Coll 2003) tests, represent useful tools to assess the risk of exposure of ecosystems to different physicochemical agents.…”

Intensity of Agricultural Practices and Effects on Adjacent Habitats

“…The inclusion of a “conservation headland” (solely sprayed with selective herbicides) is being implemented in Britain and several other European countries (, Sotherton 1990). In Canada the labelling of many recently registered herbicides prescribes an unsprayed buffer zone between the last swath and habitats such as woodlots, hedgerows, wetlands, streambanks, etc., based on evaluation of phytotoxicity data provided by pesticide registrants (Boutin et al 1995). Such label improvements must be enforced if they are to be truly effective, and should be accompanied by additional informative pamphlets to the farming community in order to divulge the rationale and salient points related to this label requirement.…”

Methods for assessing the toxicity of herbicides to submersed aquatic plants

“…However, in a limited number of cases, regulatory authorities are concerned that the mode of action of certain compounds (e.g. auxin simulators) may require further investigation if the standard test species are not thought to be appropriate 3–5. Furthermore, if potential risks are identified in the lower tiers, testing of additional species may be warranted in order to refine the risk assessment.…”

“…have also been investigated 8–11. Further reviews of the option for the use of aquatic higher plants for pesticide toxicity have been reported,3, 12–14 noting that Myriophyllum spp. and Elodea spp.…”