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Hexanoic acid, 2-ethyl-, C16-18 alkyl esters (CAS No. 90411-68-0) is a substance of unknown, variable composition or biological origin (UVCB). The substance is hydrolytically stable and therefore abiotic hydrolysis is not a relevant pathway in water. However, the substance is readily biodegradable and will rapidly be removed from natural water compartments as well as from wastewater in sewage treatment plants. The substance has a log Koc > 5 indicating a potential to adsorb to soil and sediment particles. The estimated half time for the reaction with OH-radicals is 13-14 hours (24h day; OH-concentration: 0.5E+06 OH/cm3). However, photodegradation is not an important environmental fate process since the substance is not expected to evaporate into the atmosphere due to its very low vapor pressure of < 0.01 Pa at 20 °C. Due to its low water solubility (< 0.15 mg/L in aqua bidest), ready biodegradability and potential for adsorption to soil and sediment particles, only low concentrations of Hexanoic acid, 2-ethyl-, C16-18 alkyl esters are expected to be released into the aquatic environment. The substance will be bioavailable to aquatic organisms mainly via feed and contact with suspended organic particles. Hexanoic acid, 2-ethyl-, C16-18 alkyl esters is not bioaccumulative, based on the criteria given in Regulation (EC) No. 1907/2006, Annex XIII, 1.1.2 (BCF < 2000 L/kg). After uptake by fish species, extensive and fast biotransformation of the substance by carboxylesterases into 2 ethylhexanoic acid and the corresponding alcohol is expected. BCF/BAF values estimated with the BCFBAF v3.01 program, Arnot-Gobas model including biotransformation, also indicate that this substance will not be bioaccumulative.

In conclusion, Hexanoic acid, 2-ethyl-, C16-18 alkyl esters is effectively removed from the environment by biotic degradation processes. Due the low water solubility and high adsorption potential, the main route of exposure for aquatic organisms such as fish will be via food ingestion or contact with suspended solids. Ingested amounts of the substance in organisms are expected to be effectively metabolized to 2 ethylhexanoic acid and fatty alcohols C16-C18.