Passive dosing: Assessing the toxicity of individual PAHs and recreated mixtures to the microalgae Raphidocelis subcapitata

• Published in: Aquatic toxicology 2022-08, Vol.249, p.106220-106220, Article 106220
• Main Authors: Kreutzer, Anne, Faetsch, Sonja, Heise, Susanne, Hollert, Henner, Witt, Gesine
• Format: Article
• Language: English
• Subjects: Algal growth inhibition; Mixture toxicity; Passive dosing; Polycyclic aromatic hydrocarbons; R. subcapitata
• ISSN: 0166-445X; 1879-1514
• DOI: 10.1016/j.aquatox.2022.106220

•Passive dosing offers important advantages for testing of HOCs in aquatic media•EC50 values for single PAHs were obtained using a dose-response relationship•Recreated pore water mixtures (∑10 PAHs) caused strong growth-inhibiting effects•Close relationship between toxicity of HOCs and their chemical activity was shown Risk assessment of hydrophobic organic compounds (HOCs) is difficult because maintaining a well-defined exposure during aquatic toxicity testing is challenging due to the limited water solubility and various loss processes such as volatilization, biodegradation and sorption. Passive dosing techniques help to overcome these challenges by providing a well-controlled and solvent-free exposure. In this study, the algal growth inhibition test (DIN EN ISO 8692) was converted into a miniaturized passive dosing setting. For this purpose, biocompatible O-rings were used as substance reservoirs and loaded with polycyclic aromatic hydrocarbons (PAHs). The growth inhibition of the microalgae Raphidocelis subcapitata induced by single PAHs (log KOW 3.24–5.91) was investigated. In addition, recreated PAH mixtures were tested representing field compositions of the pore water North Sea sediments. Some of the single PAHs revealed strong growth inhibiting effects on the algal growth, while the recreated mixture compositions had slightly lower effect on the growth inhibition in the highest concentrations. Overall, the toxicity of the PAHs generally increased with the maximum chemical activities (amax) of the PAHs and the inhibition data could be fitted with one maximum chemical activity response curve. Therefore, the miniaturized passive dosing approach appears as a promising practical and economical method that can be used for toxicity testing of the different trophic levels to improve comprehensive risk assessment.