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Toxicity to microorganisms

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Description of key information

The TT (toxicity threshold) value of 2-chlorobenzonitrile is 43 mg/L for

Pseudomonas putida. The 18-h EC50 and NOEC for Pseudomonas putida were determined to be 112 mg/L and 31 mg/L, respectively.
The 48-h EC50 of 2-chlorobenzonitrile to Tetrahymena pyriformis was determined to be 71 mg/L in the TETRATOX-Test.

Key value for chemical safety assessment

EC50 for microorganisms:
71 mg/L
EC10 or NOEC for microorganisms:
31 mg/L

Additional information

2-chlorobenzonitrile was investigates for its ability to inhibit the cell multiplication of the bacteria species Pseudomonas putida and growth of the ciliate Tetrahymena pyriformis, respectively.

Cultures of Pseudomonas putida bacteria were exposed to dilution series of 2-chlorobenzonitrile. Samples of 2-chlorobenzonitrile dilutions taken for analysis of the actual concentrations, revealed that the bacteria were exposed to concentrations ranging from 0.2 to 500 mg 2-chlorobenzonitrile per litre.

After incubation the extinction value of the bacterial cell suspensions were measured and a toxicity threshold value of 2-chlorobenzonitrile of 43 mg/L for Pseudomonas putida was determined. The 'Bewertungszahl' (Assessment figure or value for bacteriotoxicity) is therefore 4.4 (Bewertung Wassergefährdender Stoffe, 1979).

The EC10 and EC50 of 2-chlorobenzonitrile as well as the NOEC and LOEC were calculated by using probit analysis and the Williams-Test, respectively, on the data presented by Coenen, 1989. The following results were presented:

·        EC10 (18 h) =        43 mg/L

·        EC50 (18 h) =       112 mg/L

·        LOEC (18 h) =        63 mg/L

·        NOEC (18 h) =        31 mg/L

The toxicity of 2-chlorobenzonitrile to the freshwater ciliate Tetrahymena pyriformis was determined in a 48-h TETRATOX-Test. 0.75 % DMSO was used as vehicle. At this concentration DMSO was stated to have no toxic effects on the population growth of Tetrahymena pyriformis.

The 48-h EC50 was determined to be 71 mg/L (nominal concentration).

 

In a test according to OECD 301B (see IUCLID section 5.2.1) to determine ready biodegradability, 2-chlorobenzonitrile had no toxic effects on the activated sludge microorganisms at concentrations of 10 mg/L and 21 mg/L for a total test duration of 28 days.

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