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Toxicity to microorganisms

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Description of key information

In a guideline (OECD 209) and GLP study by Brixham Environmental Laboratory (2009) the 30 -min EC50 for acetonitrile in an Activated Sludge Respiration Inhibition Test was determined to be >1000 mg/L and the NOEC was 320 mg/L.  Previous data on the toxicity of acetonitrile to aquatic microorganisms was evaluated in the EU RAR.  Reported toxicity values ranged from 73 mg/L to 28,000 mg/L.  The lowest value by an order of magnitude was reported by Blum and Speece (1991), a 24-hour IC50 of 73 mg/L in Nitrosomas sp., based on inhibition of ammonia consumption.  

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
320 mg/L

Additional information

In a guideline (OECD 209) and GLP study by Brixham Environmental Laboratory (2009) the 30 -min EC50 for acetonitrile in an Activated Sludge Respiration Inhibition Test was determined to be >1000 mg/L, and the NOEC was 320 mg/L.

Previous data on the toxicity of acetonitrile to microorganisms was reviewed in the EU Risk Assessment Report (2000). A summary of these data is shown in the table below. Blum and Speece (1991) present data on three groups of environmental bacteria that can be relevant when considering the microbial activity of domestic WWTPs. The IC50 values (the concentrations of acetoni­trile causing 50% bacterial inhibition compared to controls) are considered valid for this assessment and were summarized as follows:

           1. Aerobic heterotrophs.- These bacteria predominate in activated sludge systems and in natural aerobic environments where they convert organic material to carbon dioxide and water. The inhibition in oxygen uptake by the bacteria was monitored after 15 hours exposure and used to calculate and IC50 of 7500 mg/L.

           2.Nitrosomas sp.- These bacteria convert ammonia nitrogen to nitrite as the first most sensitive step in the biologi­cal oxidation of inorganic nitrogen. The inhibition in ammonia consumption by the bacteria was monitored after 24 hours exposure and used to calculate an IC50 of 73 mg/L.

           3. Methanogens.- Methanogens form part of the consortium of bacteria that convert organic matter to carbon dioxide and methane under anaerobic conditions. The inhibition of gas production by the bacteria was monitored after 48 hours exposure and used to calculate an IC50 of 28000 mg/L.

Additional data on (Pseudomona putida),and several protozoa species have been published by Brigmann and Kühn (1980ª, 1980b, 1981). The lowest toxicity threshold is 680 mg/l reported for (P. putida), while TT values for protozoa species are in the range of g/l.

 

Toxicity of acetonitrile to aquatic microorganisms (EU Risk Assessment Report, 2000)

SPECIES

TEST TYPE

COMMENTS

DURATION

(hour)

TOXICITY

END POINT

(mg/l)

REFERENCE

Chillmonas paramecium(Protozoa)

Inhibition of cell multiplication

Valid as additional information

48

TT = 942

Bringmann and Kühn (1981)

 

Entosiphon sulcatum(Protozoa)

Inhibition of cell multiplication

Valid as additional information

72

TT = 1810

Bringmann and Kühn (1980a)

 

Pseudomona putida(Bacteria)

Inhibition of cell multiplication

Valid as additional information

16

TT = 680

Bringmann and Kühn (1980a)

 

Uronema parduzci(Protozoa)

Inhibition of cell multiplication

Valid as additional information

20

TT = 5825

Bringmann and Kühn (1980b)

 

Nitrosomas

(Bacteria)

Inhibition of ammonia consumption

Valid for the assessment

24

IC50= 73

Blum and Speece (1991)

Aerobic micro-organisms

Inhibition of oxygen uptaque AFNOR and ETAD

Valid for the assessment

15

IC50= 7500

Blum and Speece (1991)

Metanogenic bacteria

Inhibition of gas production

Valid for the assessment

48

IC50= 28000

Blum and Speece (1991)

 TT = toxicity threshold