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Toxicity to microorganisms

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Reference
Endpoint:
toxicity to microorganisms, other
Remarks:
Biodegradation in water: screening test, toxicity control is used to derive effect concentration
Type of information:
experimental study
Adequacy of study:
key study
Study period:
22 March 2018 - 19 April 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
other: OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Version / remarks:
1992
Deviations:
no
Principles of method if other than guideline:
Biodegradation in water: screening test, toxicity control is used to derive effect concentration
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
no
Vehicle:
yes
Remarks:
acetone
Details on test solutions:
A nominal amount of test item (1000 mg) was dissolved in 10 mL of acetone to give a 1000 mg/10 mL solvent stock solution. An aliquot (500 µL) of this solvent stock solution was dispensed onto a filter paper and the solvent allowed to evaporate to dryness for approximately 15 minutes. The filter paper was dispersed in approximately 350 mL of mineral medium with the aid of high shear mixing (approximately 7500 rpm, 5 minutes) prior to addition of inoculum. The volume was then adjusted to 500 mL to give a final concentration of 100 mg/L. The volumetric flask containing the solvent stock solution was inverted several times to ensure homogeneity of the solution.
Test organisms (species):
sewage, domestic
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): A mixed population of sewage treatment micro-organisms was obtained on 19 March 2018 from the final effluent stage of the Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK, which treats predominantly domestic sewage.
- Preparation of inoculum for exposure: The sample of effluent was filtered through coarse filter paper (first approximate 200 mL discarded) and maintained on aeration in a temperature controlled room at temperatures of between 16 and 21 ºC prior to use.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
28 d
Test temperature:
20 - 22 ºC
pH:
7.4 - 7.6 at test start
Nominal and measured concentrations:
100 mg/L
Details on test conditions:
TEST CONDITIONS
- Composition of medium: mineral medium as recommended in the OECD Guidelines
- Solubilising agent (type and concentration if used): acetone
A nominal amount of test item (1000 mg) was dissolved in 10 mL of acetone to give a 1000 mg/10 mL solvent stock solution. An aliquot (500 µL) of this solvent stock solution was dispensed onto a filter paper and the solvent allowed to evaporate to dryness for approximately 15 minutes. The filter paper was dispersed in approximately 350 mL of mineral medium with the aid of high shear mixing (approximately 7500 rpm, 5 minutes) prior to addition of inoculum. The volume was then adjusted to 500 mL to give a final concentration of 100 mg/L. The volumetric flask containing the solvent stock solution was inverted several times to ensure homogeneity of the solution.
- Test temperature: 20 - 22 ºC
- pH: 7.4 - 7.6 at test start
- pH adjusted: no
- Continuous darkness: diffuse light


TEST SYSTEM
- Culturing apparatus: CES Multi-Channel Aerobic Respirometer
- Number of culture flasks/concentration: 3

SAMPLING
- Sampling frequency: daily

CONTROL AND BLANK SYSTEM
Three replicate bottles containing inoculated mineral medium to act as the inoculum control plus a filter paper.
Two replicate bottles containing inoculated mineral medium plus a filter paper and the reference item, aniline, at a concentration of 100 mg/L.
Two replicate bottles containing the test item on filter paper at a concentration of 100 mg/L in inoculated mineral medium plus the reference item, aniline, at a concentration of 100 mg/L to act as toxicity control vessels.

Reference substance (positive control):
no
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Details on results:
CGE-PMDA adduct attained 0% biodegradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No. 301F.
The toxicity control attained 31% biodegradation after 14 days and 34% biodegradation after 28 days thereby confirming that the test item was not toxic to the sewage treatment micro-organisms used in the test.
Aniline (procedure control) attained 67% biodegradation after 14 days and 76% biodegradation after 28 days thereby confirming the suitability of the inoculum and test conditions.
Validity criteria fulfilled:
yes
Conclusions:
The toxicity control attained 31% biodegradation after 14 days and 34% biodegradation after 28 days thereby confirming that CGE-PMDA adduct (100 mg/L) was not toxic to the sewage treatment micro-organisms used in the test.
Executive summary:

The toxicity of CGE-PMDA adduct to microorganisms was assessed in a study according to OECD Guideline 301F, “Ready Biodegradability; Manometric Respirometry Test” referenced as method C.4-D of Commission Regulation (EC) No. 440/2008 and US EPA Fate, Transport, and Transformation Test Guidelines OCSPP 835.3110 (Paragraph (q)).

The test item at a concentration of 100 mg/L was exposed to sewage treatment micro-organisms with mineral medium in sealed culture vessels in diffuse light at temperatures of between 20 and 22 ºC for 28 days. 

Following the recommendations of the International Standards Organisation (ISO 1995), the test item was dissolved in an auxiliary solvent prior to being adsorbed onto a filter paper and subsequent dispersal in test media. Using this method the test item is evenly distributed throughout the test medium and the surface area of test item exposed to the test organisms is increased thereby increasing the potential for biodegradation.

The biodegradation of the test item was assessed by the measurement of daily oxygen consumption values on Days 0 to 28. Control solutions with inoculum and the reference item, aniline, together with a toxicity control were used for validation purposes.

CGE-PMDA adduct attained 0% biodegradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No. 301F.

The toxicity control attained 31% biodegradation after 14 days and 34% biodegradation after 28 days thereby confirming that the test item was not toxic to the sewage treatment micro-organisms used in the test.

Aniline (procedure control) attained 67% biodegradation after 14 days and 76% biodegradation after 28 days thereby confirming the suitability of the inoculum and test conditions.

Description of key information

The toxicity control attained 31% biodegradation after 14 days and 34% biodegradation after 28 days thereby confirming that CGE-PMDA adduct (100 mg/L) was not toxic to the sewage treatment micro-organisms used in the test.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
100 mg/L

Additional information

The toxicity of CGE-PMDA adduct to microorganisms was assessed in a study according to OECD Guideline 301F, “Ready Biodegradability; Manometric Respirometry Test” referenced as method C.4-D of Commission Regulation (EC) No. 440/2008 and US EPA Fate, Transport, and Transformation Test Guidelines OCSPP 835.3110 (Paragraph (q)).

The test item at a concentration of 100 mg/L was exposed to sewage treatment micro-organisms with mineral medium in sealed culture vessels in diffuse light at temperatures of between 20 and 22 ºC for 28 days. 

Following the recommendations of the International Standards Organisation (ISO 1995), the test item was dissolved in an auxiliary solvent prior to being adsorbed onto a filter paper and subsequent dispersal in test media. Using this method the test item is evenly distributed throughout the test medium and the surface area of test item exposed to the test organisms is increased thereby increasing the potential for biodegradation.

The biodegradation of the test item was assessed by the measurement of daily oxygen consumption values on Days 0 to 28. Control solutions with inoculum and the reference item, aniline, together with a toxicity control were used for validation purposes.

CGE-PMDA adduct attained 0% biodegradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No. 301F.

The toxicity control attained 31% biodegradation after 14 days and 34% biodegradation after 28 days thereby confirming that the test item was not toxic to the sewage treatment micro-organisms used in the test.

Aniline (procedure control) attained 67% biodegradation after 14 days and 76% biodegradation after 28 days thereby confirming the suitability of the inoculum and test conditions.