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Toxicity to microorganisms

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Description of key information

Two studies are available which were rated with Klimisch 2 (reliable, with restrictions) were used in a weight-of-evidence (WoE) approach to derive PNEC STP. Fabig (1988) reported an 18 h-EC10 of > 320 mg/L (highest test concentration) with Pseudomonas putida. This study is not the same as an activated sludge respiration test according to OECD 209 but there is indication of no toxicity towards P. putida as a microorganism.

Stone and Watkinson (1983) as well is not an OECD 209 study but investigated biodegradation with an bacteria growth inhibition test with Pseudomonas fluorescens. The IC50 was reported as 54.4 mg/L.

Both studies were used in a WoE approach. The REACH guidance document R.10 specifies that studies with P. fluorescens are of limited relevance for STP as this species uses glucose as substrate. However, a growth inhibition test with P. putida may be used for PNEC STP derivation. The study of Fabig (1988) was conducted in accordance with DIN 38412-8 while the recent REACH guidance document R.10 asks for ISO-10712 (1996). Despite the fact that it is not totally certain if the DIN translated directly into the ISO the study is considered sufficiently reliable to be used in a WoE approach. Thus, the EC10 > 320 mg/L was used for PNEC derivation. This approach was also taken in the European Risk Assessment report (2010).

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
320 mg/L

Additional information