title: Aquatic toxicity testing of liquid hydrophobic chemicals - Passive dosing exactly at the saturation limit.
abstract: The aims of the present study were (1) to develop a passive dosing approach for aquatic toxicity testing of liquid substances with very high Kowvalues and (2) to apply this approach to the model substance dodecylbenzene (DDB, Log Kow= 8.65). The first step was to design a new passive dosing format for testing DDB exactly at its saturation limit. Silicone O-rings were saturated by direct immersion in pure liquid DDB, which resulted in swelling of >14%. These saturated O-rings were used to establish and maintain DDB exposure exactly at the saturation limit throughout 72-h algal growth inhibition tests with green algae Raphidocelis subcapitata. Growth rate inhibition at DDB solubility was 13 ± 5% (95% CI) in a first and 8 ± 3% (95% CI) in a repeated test, which demonstrated that improved exposure control can lead to good precision and repeatability of toxicity tests. This moderate toxicity at chemical activity of unity was higher than expected relative to a reported hydrophobicity cut-off in toxicity, but lower than expected relative to a reported chemical activity range for baseline toxicity. The present study introduces a new effective approach for toxicity testing of an important group of challenging chemicals, while providing a basis for investigating toxicity cut-off theories.
authors: Institute for Environmental Research (Biology V), RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany; Department of Environmental Engineering, Technical University of Denmark, Bygningstorvet B115, DK-2800 Kongens Lyngby, Denmark. Electronic address: felix.stibany@rwth-aachen.de.
authors: Felix
authors: F
authors: Stibany
authors: Department of Environmental Engineering, Technical University of Denmark, Bygningstorvet B115, DK-2800 Kongens Lyngby, Denmark.
authors: Stine Nørgaard
authors: SN
authors: Schmidt
authors: Institute for Environmental Research (Biology V), RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany.
authors: Andreas
authors: A
authors: Schäffer
authors: Department of Environmental Engineering, Technical University of Denmark, Bygningstorvet B115, DK-2800 Kongens Lyngby, Denmark.
authors: Philipp
authors: P
authors: Mayer
mesh_terms: D001555:Benzene Derivatives / Q000737:chemistry / Q000633:toxicity*; D000460:Chlorophyta / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D057927:Hydrophobic and Hydrophilic Interactions; D008962:Models, Theoretical; D012828:Silicones / Q000737:chemistry; D012995:Solubility; D018675:Toxicity Tests / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000633:toxicity*
chemical_list: D001555:Benzene Derivatives; D012828:Silicones; D014874:Water Pollutants, Chemical; C041588:dodecylbenzene
keywords: Algal growth inhibition; Highly hydrophobic liquids; Hydrophobicity cut-off; Passive dosing; Saturation limit; Silicone swelling