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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

3h EC50 (activated sludge, domestic) = 135 mg/L (respiration inhibition test, similar to OECD 209)

Key value for chemical safety assessment

EC50 or LC50 for microorganisms:
135 mg/L

Additional information

One reliable GLP study on toxic effects of C12-isoAS Na (CAS 94200-74-5) to microorganisms is available (Leuschner 1998). The test was performed according DIN 38412, part 8 guideline. The EC10 value based on inhibition of cell multiplication determined after 16-hour exposure to the test substance was above 1000 mg/L (nominal concentration). Nevertheless, the results of activated sludge respiration inhibition test performed with another C12 homologue - C12AS Na (CAS 151-21-3), are available (Dutka 1983). Since the preference is given to tests with a mixed inoculum that assess the functioning of the entire microbial community in an STP, rather than tests based on single species or even microbial sub-systems, this test is considered to be the key study. Therefore, in accordance with Regulation (EC) 1907/2006 Annex XI, 1.5, a read-across to other structurally related category members was conducted. The non-GLP test was performed with activated sludge from a municipal sewage treatment plant according to a guideline similar to OECD 209. The EC50 values of 188 and 135 mg/L (nominal concentrations) were obtained for the endpoint respiration inhibition after 30 minutes and 3 hours of exposure, respectively. The 3-hour EC50 value of 135 mg/L was used for PNEC STP derivation for CAS 94200-74-5. In the supporting non-GLP study with CAS 151-21-3, Dutka and Kwan (1984) used synthetic activated sludge and measured respiration rate after 3 hours. The 3h IC50 value was 480 mg/L (nominal concentration). Moreover, a GLP test according to DIN 38412 part 8 with Pseudomonas putida using C12-14AS TEA (CAS 90583-18-9) is available (Guhl 1992). In this study, the growth inhibition of Pseudomonas putida was recorded after approximately 16 hours of exposure. The 16-h EC10 value was determined to be 1084 mg a.i./L (nominal concentration). Due to structural and property similarities with the tested category members it can be concluded that the above results apply also to C12-isoAS Na (CAS 94200-74-5).