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Toxicity to microorganisms

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Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
1980
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Reference:
Composition 0
Principles of method if other than guideline:
As a method the cell multiplication inhibition test following Bringmann was applied to the model organisms.
GLP compliance:
no
Test material information:
Composition 1
Specific details on test material used for the study:
urea, no purity
Vehicle:
yes
Remarks:
double distilled water
Details on test solutions:
Test solutions were prepared in double distilled water in 300 mL Erlenmeyer flasks, stoppered with cotton-lined plastic caps. The first solution in each dilution series contained 160 mL solution. Subsequent dilutions were prepared from this one by consistently mixing 80 mL of the test solution and 80 mL double distilled water.
Test organisms (species):
Pseudomonas putida
Details on inoculum:
Stock cultures were kept on nutrient medium in agar slant tubes. New stock cultures were prepared weekly. The inoculated stock cultures were incubated at 25 °C for 24 hours.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
16 h
Test temperature:
25 °C
Nominal and measured concentrations:
Dilutions containing 1 part v/v of the test substance in 2^0 to 2^14 parts v/v of mixture, up to 10000 mg/L
Details on test conditions:
Each flask in the dilution series was inoculated to 100 mL by adding 5mLof two stock solutions, each, and 10 mL of the tested bacteria. Inoculated bacterial test solutions were incubated at 25 °C for 16 hours. After termination of the test period the extinction of the monochromatic radiation was measured.
Reference substance (positive control):
not specified
Key result
Duration:
16 h
Dose descriptor:
NOEC
Remarks:
Toxicity threshold
Effect conc.:
> 10 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth inhibition
Details on results:
The toxicity threshold / NOEC of urea after 16 h exposure was determined to be >10000 mg/L.
Validity criteria fulfilled:
not applicable
Conclusions:
The toxicity threshold / NOEC of urea was determined to be >10000 mg/L.
Executive summary:

A study testing the toxicity of an array of pollutants on different bacteria was performed using Bringmann method of cell multiplication inhibition test. Pseudomonas putida bacteria were exposed for 16 hours to the test item - urea at concentration levels up to 10000 mg/L. No toxic effects on the bacteria were observed. The toxicity threshold (NOEC) was determined after 16 h to be >10000 mg/L.

Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
1983
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Reference:
Composition 0
Principles of method if other than guideline:
Cell multiplication inhibition test according to Bringmann and Kühn. Biomass growth inhibition measured turbidimetrically with cell concentration expressed as extinction of light. Measurements performed according to the procedure described in Bringmann, G. and Kühn, R. (1979) in Umweltbundesamt, Berlin, LTws-Nr.10, 23-28.
GLP compliance:
no
Test material information:
Composition 1
Specific details on test material used for the study:
Hydrogen peroxide, H2O2
CAS 7722-84-1
Analytical monitoring:
not specified
Test organisms (species):
Pseudomonas putida
Details on inoculum:
DSM-Nr. 50026
Test type:
static
Water media type:
freshwater
Total exposure duration:
18 h
Nominal and measured concentrations:
Not specified
Details on test conditions:
A cell multiplication inhibition test was performed according to Brigmann/Kühn method. The microorganisms were exposed to the test solution for 16 - 18 hours.
Reference substance (positive control):
not specified
Key result
Duration:
18 h
Dose descriptor:
EC10
Effect conc.:
11 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth inhibition
Details on results:
The EC10 was determined to be 11 mg/L.
Validity criteria fulfilled:
not specified
Conclusions:
The EC10 was determined to be 11 mg/L.
Executive summary:

A test according to Brigmann/Kühn was perfomed to determine the growth inhibition of hydrogen peroxide on the tested microorganisms Pseudomonas Putida. The exposure period was 16 - 18 hours. After the exposure period was over the cell multiplication inhibition was measured turbidimetrically with cell concentration expresed as extinction of light. The EC10 of the test substance was determined to be 11 mg/L.

Endpoint:
activated sludge respiration inhibition testing
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
Please refer to section 13 for "Read-Across justification".
Reason / purpose:
read-across source
Related information:
Composition 1
Test material information:
Composition 1
Key result
Duration:
18 h
Dose descriptor:
EC10
Effect conc.:
11 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth inhibition
Remarks on result:
other: species: Pseudomonas putida
Endpoint:
activated sludge respiration inhibition testing
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
Please refer to section 13 for "Read-Across justification".
Reason / purpose:
read-across source
Related information:
Composition 1
Test material information:
Composition 1
Key result
Duration:
16 h
Dose descriptor:
NOEC
Remarks:
Threshold toxicity
Effect conc.:
> 10 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth inhibition
Remarks on result:
other: species: Pseudomonas putida

Description of key information

The EC10 of the degradation product H2O2 was considered to be 11 mg/L.

Key value for chemical safety assessment

EC10, LC10 or NOEC for microorganisms:
11 mg/L

Additional information

The toxicity to microorganisms of the test item was addressed with a read-across approach to its degradation products - urea and hydrogen peroxide. The test item is not stable and decomposes rapidly to urea and H2O2, therefore, the read-across to both substances is considered acceptable.

Publications reporting the toxicity to microorganisms of urea and hydrogen peroxide were used in a read-across weight of evidence approach.

Urea

A study testing the toxicity of an array of pollutants on different bacteria was performed using Bringmann method of cell multiplication inhibition test. Pseudomonas putida bacteria were exposed for 16 hours to the test item - urea at concentration levels up to 10000 mg/L. No toxic effects on the bacteria were observed. The toxicity threshold (NOEC) was determined after 16 h to be >10000 mg/L.

Hydrogen peroxide (H2O2)

A test according to Brigmann/Kühn was perfomed to determine the growth inhibition of hydrogen peroxide on the tested microorganisms Pseudomonas putida. The exposure period was 16 - 18 hours. After the exposure period was over the cell multiplication inhibition was measured turbidimetrically with cell concentration expresed as extinction of light. The EC10 of the test substance was determined to be 11 mg/L.

In conclusion, the toxicity to microorganisms of the test item hydrogen peroxide-urea (1:1) is based on the toxic effects which H2O2 showed in the growth inhibition test, as urea is not toxic to microorganisms. The EC10 of the test item is considered to be 11 mg/L.