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Toxicity to aquatic algae and cyanobacteria

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Cross reading from B-stof: In order to predict effects of chemicals in an aquatic environment, the toxicity to freshwater algae was assessed. The algal toxicity was determined in the algal growth inhibition test in accordance with OECD, EEC and ISO test guidelines and with the OECD Principles of GLP. The guidelines were slightly modified to ensure good growth and pH control of the cultures. 
The toxicity of B-stof to exponentially growing culture of Pseudokirchneriella subcapitata (formerly known as Selenastrum capricornutum) was determined over an exposure period of 72h. The green algae P. subcapitata was exposed to 1000 mg/L of B-stof and no toxicity was observed. The test was conducted in a mineral salts medium in a climatized illuminated orbital incubator. The maximum variation in pH in the test media was 1.1 pH unit. The definitive test is valid as shown by the increase of the control cell number over 72h by a factor of 179. Based on the results obtained it can be concluded that the NOEC of P. subcapitata for B-stof > 391 mg/L (based on geometric mean between the measured concentrations of B-stof at the beginning and the end of the study). Chemical analyses from the beginning and the end of the test show that B-stof was not stable under algae test conditions. The measured concentrations of B-stof were 1.02 g/L at the beginning of the test and 0.15 g/L after 72h of testing, perhaps due to the photodegrading propertiy of the test substance.

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