Fenvalerate aquatic organisms

Lethal and sublethal effects of fenvalerate on aquatic organisms... 

Fenvalerate is extremely toxic to representative nontarget aquatic organisms and to some beneficial terrestrial arthropods at concentrations substantially lower than those recommended to control pestiferous insects. Toxic effects are associated primarily with the 2.S, a.S -isomcr and are exacerbated at low temperatures. Birds, mammals, and terrestrial plants are normally tolerant. 

Supertoxic compounds are those with LC50 (96h) values <10pg/L (Scott etal. 1987). Fenvalerate is considered supertoxic, as judged by LC50 (96 h) values of <1.0 pg/L for sensitive aquatic organisms, and <10 pg/L for representative aquatic species (Table 20.5). 

Table 20.5 Lethal and Sublethal Effects of Fenvalerate on Aquatic Organisms ... 

More research is also needed on indirect effects on wildlife due to reductions in nontarget insects, and on bioavailability of fenvalerate to aquatic organisms from sediments and the sediment-water interface. 

Laboratory studies with fenvalerate and aquatic organisms indicate marked differences in sensitivity (among taxonomic groups). Cmstaceans were the most sensitive... 

Despite the high toxicity of fenvalerate and other pyrethroids to aquatic organisms, few environmental problems have been documented, presumably due to the very low application levels needed to control insects, adsorption onto soil and organic matter, and comparatively rapid degradation. Nevertheless, fenvalerate is extremely toxic to aquatic organisms (Table 16.2), has high bioaccumulation, and is persistent in sediments ... 

In the last century, the development of organophosphorus, carbamate, and organochloride insecticides was followed by synthetic pyrethroids. As a result, pyrethroids are now used frequently in the domestic milieu. Pyrethroid insecticides are synthetically derived from the molecular structure or sharing the same mechanism of action of natural pyrethrins that have broader spectmm of activity, more stability, and residual activity (persists longer than that of natural pyrethrins) and include the following allethrin, cyfluthrin, cyhalothrin, cypermethrin, deltamethrin, fenvalerate, flumethrin, fluvalinate, tau-fluvalinate, and permethrin (see structure in Fig. 137.2). They are lipophilic compounds and generally of low acute oral toxicity to mammals but are very toxic to aquatic organisms. When synthetic pyrethroids are administered to mammals parenterally, the synthetic pyrethroids are neurotoxic. 

Bioaccumulation factors for fenvalerate by representative freshwater and estuarine organisms during exposure for 28 to 30 days to various sublethal doses ranged from 40 to 570 for fish, 356 to 4700 for invertebrates, and 477 to 933 for algae (Smith and Stratton 1986). Because of its unusually high lipophilicity, fenvalerate is accumulated at only 30% efficiency by aquatic fauna, and uptake is not dose dependent (Coats et al. 1989). Contamination of algal food of daphnids with fenvalerate does not seem to contribute to an increase in whole-body burdens, although reduced filtration rates... 

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