Aquatic organisms can be exposed to pyrethroid insecticides present in the water column and pore water, and sorbed to the food and sediment particles they consume. Accumulation in organisms is dependent not only on the concentrations present in the environment, but also on chemical bioavailability. Pyrethroids are highly hydrophobic compounds with log K<sub>OW</sub> &gt;6. Within aquatic systems, these compounds associate strongly with aquatic plants, sediments, and dissolved organic carbon (DOC) in the water column and sediment pore water. The partitioning of pyrethroids to DOC and organic materials dramatically reduces the fraction of freely dissolved, bioavailable chemical. Equilibrium partitioning (EqP) relationships between bioavailable concentrations in water and sediment pore water and organism lipid content are used to estimate chemical accumulation in organisms, independent of the exposure route. EqP theory has been applied to pyrethroids to relate aqueous uptake and toxicity to freely dissolved pyrethroids in water and sediment pore water. Ingestion of pyrethroids sorbed to sediment particles or food represents another potential route of exposure. An examination is being conducted to determine the relative contributions of aqueous and dietary uptake to pyrethroid accumulation at aquatic trophic levels ranging from primary consumers such as benthic invertebrates, to predatory fish trophic groups such as benthivores and piscivores. Regardless of the route of exposure, studies have shown that aquatic organisms do not accumulate pyrethroids significantly because metabolic transformation to nontoxic degradates rapidly reduces concentrations within the body.

Examination of the relative contributions of aqueous and dietary uptake to pyrethroid accumulation in organisms at different aquatic trophic levels

253rd National Meeting (2017)

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