Invertebrates pyrethroid insecticides

Schroer AFW, Belgers D, Brock TCM, Matser A, Maund SJ, van den Brink PJ. 2004b. Comparison of laboratory single species and field population-level effects of the pyrethroid insecticide lambda-cyhalothrin on freshwater invertebrates. Arch Environ Contam Toxicol 46 324-335. 

Mesocosm no-effect data on a rapidly dissipating compound such as a pyrethroid insecticide may not be suitable for a chronic EQS applied to a river. Furthermore, most existing micro- and mesocosm studies are inappropriate for EQS derivation if fish are the most sensitive species because fish have generally been excluded from such tests. There is consequently a need for evidence-based decision making for interpretation of nonstandard mesocosm studies. Microcosm and mesocosm tests can, however, be used directly for EQS derivation if algae, macrophytes, and invertebrates are appropriately represented in the test systems and if they concern substances subject to transient exposure. They are then directly applicable for the derivation of M AC-EQSs. For this purpose, the NOEAEC can be used as it represents the highest initial concentration that causes no ecologically relevant effects. 

Pyrethroids show very marked selective toxicity (Table 12.2). They are highly toxic to terrestrial and aquatic arthropods and to fish, but only moderately toxic to rodents, and less toxic still to birds. The selectivity ratio between bees and rodents is 10,000- to 100,000-fold with topical application of the insecticides. They therefore appear to be environmentally safe so far as terrestrial vertebrates are concerned. There are, inevitably, concerns about their possible side effects in aquatic systems, especially on invertebrates. 

The major inhibitory neurotransmitter in invertebrates is Y-aminobutyric acid (GABA). Inhibitory neurones are found both in the CNS and at the neuromuscular junction in invertebrates (1), whereas they are not found at the neuromuscular junction in mammals. The widespread distribution of GABA-ergic neurones in insects is probably partly responsible for the selective toxicity towards insects of certain commercial insecticides, e.g., cyclodienes (2-41. avermectin (5), and perhaps some pyrethroids ( ). 

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