Bioconcentration, Bioaccumulation, and Metabolism of Pesticides in Aquatic Organisms

From the viewpoint of protecting the natural environment, aquatic ecotoxicological assessment of new pesticides and many existing ones has increasingly become more important. To assess the impact of pesticides on aquatic organisms, international authorities (utilizing OECD and USEPA testing guidelines) require completion of many acute and chronic ecotoxicological studies. Among such studies is testing to measure the potential for bioconcentration. In addition, the authorities in these agencies insist that physico-chemical properties and environmental fate be determined for each registered pesticide. The rationale for such testing is based on the concept that, even if used in conformance with good agricultural practices, pesticides may enter surface waters by several routes such as spray drift, surface runoff, and field drainage, and they may be partitioned to bottom sediments (Katagi 2006). The endpoints of such ecotoxicological testing include mortality and effects on hatching, development, and reproduction. Such endpoints are usually expressed as median-lethal or median-effect concentrations (LC50 and EC50) and no-observed-effect-concentrations (NOEC); such values can be compared with predicted environmental concentrations in exposure media for purposes of risk assessment (Miyamoto et al. 2008). Because aquatic organisms interact with each other in the food web, knowledge of their tendency to bioconcentrate residues in water and from dietary exposure is important when evaluating real environmental pesticide effects. In general, bioconcentration is the most popular term for describing the process by which pesticides enter organisms directly from water through the gills or through epithelial tissues. In contrast, bioaccumulation includes the effect of dietary uptake through food consumption or intake of bottom sediments (Miyamoto et al. 1990). When the levels of a pesticide, accumulated by organisms, are concentrated through two or more trophic levels in a food web, the process is referred to as biomagnification (Connell 1988). © 2010 Springer Science+Business Media, LLC.