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Toxicity to aquatic algae and cyanobacteria

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Description of key information

The data used to characterize the acute aquatic toxicity of C9 aromatic hydrocarbons are from two short-term toxicity studies with Pseudokirchneriella subcapitata, following standard test guidelines. These results indicate that C9 aromatics hydrocarbons causes moderate acute toxicity to freshwater green algae at a range of 2.9 to >= 7.9 mg/L (growth rate), and 2.6 to >= 3.8 mg/L (biomass), based on nominal loading of the test substance in water, and >=0.42 mg/L and >=0.29 mg/ L, respectively, based on measured concentrations

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Additional information

The toxicity of C9 aromatics hydrocarbons as measured by biomass and growth rate to the green alga (Pseudokirchneriella subcapitata formerly Selenastrum capricornutum) was evaluated in freshwater. Under the conditions of the studies, C9 aromatic hydrocarbons produced toxicity based on inhibition of growth rate at 2.9 to >= 7.9, and reduction in biomass at a range of 2.6 to >= 3.8 mg/L, based on nominal loading of the test substance in water, and >=0.42 mg/L and >=0.29 mg/ L, respectively, based on measured concentrations

In the WAF methodology, different loadings of the substance are added to the test medium and equilibrium between the water and the hydrocarbons is achieved according to their specific water solubility. The hydrocarbon concentrations at equilibrium will be characteristic of the loading of the substance, and therefore toxicity values from WAF studies are expressed as effect loadings or lethal loadings (EL or LL), not as concentrations. These effect loadings are used to determine environmental classifications. The WAF methodology is widely accepted for the testing of complex hydrocarbon substances and other UVCBs, and it has been incorporated in different guidance documents, including the REACH guidance (see draft decision response letter in Section 13).