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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

The inhibition of the degradation activity of activated sludge is not anticipated when introduced in appropriate low concentrations. 

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Additional information

A study on toxicity of caffeine to microorganisms (P. pudita) is available. Furthermore a guideline study investigating an analogue test substance (Theophylline, CAS No.: 58-55-9) was carried out using activated sludge.

In a guideline study similar to German standard DIN 38412, part 8, the toxicity of caffeine to Pseudomonas putida was investigated. In a 17 hour test the growth rate of P. putida in treatments with the following nominal concentrations 156.25, 312.5, 625, 1250, 2500, 5000, 7500 and 10000 mg/L was determined and compared to the growth rate of the bacterium in a control. The EC50 for P. putida was 3490 mg/L.

In a 180 min respiration inhibition test according to OECD guideline 209, the effect of theophylline on the respiration rate of activated sludge taken from a waste water treatment plant treating domestic sewage was investigated. The EC50 (180 min) for theophylline was 900 mg/L. The toxicity of theophylline is assumed to be analogue to caffeine due to structural similarities of the substances.