Registration Dossier

Environmental fate & pathways

Biodegradation in water: screening tests

Currently viewing:

Administrative data

Link to relevant study record(s)

Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
02 February 2016 - 8th June 2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
Activated sludge was collected from the Easton Wastewater Treatment Facility, Easton, Maryland on March 03, 2016. The Easton facility treats predominantly residential wastes. The sludge was sieved using a 2-mm screen, adjusted to approximately 1,000 mg total suspended solids(TSS)/L with mineral media and then aerated at test temperature until use. A total suspended solids measurement and standard plate count were performed on the inoculum on the day of test chamber preparation. Plates were incubated at 20±3ºC for approximately 48 hours.
Duration of test (contact time):
28 d
Initial conc.:
10 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
The ready biodegradability of the Substance was determined by the Carbon Dioxide Evolution Test Method (OECD Guideline 301B) over 28 dDys. In the CO2 test, inoculated mineral medium was dosed with a known amount of test substance as the nominal sole source of organic carbon and aerated with CO2-free air. The CO2 produced from the mineralization of organic carbon within the test chambers was displaced by the flow of CO2-free air and trapped as K2CO3 in KOH trapping solution. The amount of CO2 produced by the test substance (corrected for that evolved by the blank inoculum) is expressed as a percentage of the theoretical amount of CO2 (TCO2) that could have been produced if complete biodegradation of the test substance occurred. The test contained a blank control group, a reference group, a treatment group and a toxicity control. Each group contained three replicate test chambers. The blank control was used to measure the background CO2 production of the inoculum and was not dosed with a carbon source. The reference chambers were dosed with sodium benzoate, a substance known to be biodegradable, at a nominal concentration of 10 mg C/L. The treatment group test chambers were used to evaluate EXP1505385 at a nominal concentration of approximately 10 mg C/L. The toxicity control was used to evaluate toxicity of the test substance to the inoculum and was dosed with both the reference and test substances at nominal concentrations of approximately 10 mg C/L each.
Reference substance:
benzoic acid, sodium salt
Preliminary study:
The measured total organic carbon (TOC) concentration of the reference substance stock solution was 394.8 mg C/L. The volume of stock solution used to dose the reference chambers was adjusted based on the measured TOC value so that approximately 10 mg C/L was delivered.
Test performance:
The final mean percent biodegradation for the Substance was 10.7%. The Substance may not be considered readily biodegradable, since 60% TCO2 was not achieved.The toxicity control achieved > 25% degradation by Day 14 and may be considered non-inhibitory at the concentration tested in this study.
Parameter:
% degradation (CO2 evolution)
Value:
10.7
St. dev.:
4.5
Sampling time:
29 d
Remarks on result:
other: N=3
Results with reference substance:
The viability of the inoculum and validity of the test were supported by the results of the reference substance, sodium benzoate, from which an average of 91.9% of theoretical CO2 was evolved. An average percent biodegradation of greater than 60% was achieved by Day 11, thereby fulfilling the criteria for a valid test by reaching the pass level by Day 14.

See Attached Background Material

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
Evidence of ready biodegradability in a Carbon Dioxide Evolution Test is 60% TCO2 within the 28-day test period. In addition, the pass level must be reached within 10 days of achieving 10% TCO2. The final mean percent biodegradation for the substancewas 10.7% after 28 days. The Substnace may not be considered readily biodegradable, since 60% TCO2 was not achieved. The toxicity control achieved > 25% degradation by Day 14 and may be considered non-inhibitory at the concentration tested in this study.
Executive summary:

The ready biodegradability of EXP1505385 was determined by the Carbon Dioxide Evolution Test Method (OECD Guideline 301B). In the CO2test, inoculated mineral medium was dosed with a known amount of test substance as the nominal sole source of organic carbon and aerated with CO2-free air. The CO2produced from the mineralization of organic carbon within the test chambers was displaced by the flow of CO2-free air and trapped as K2CO3in KOH trapping solution. The amount of CO2produced by the test substance (corrected for that evolved by the blank inoculum) is expressed as a percentage of the theoretical amount of CO2(TCO2) that could have been produced if complete biodegradation of the test substance occurred. The test contained a blank control group, a reference group, a treatment group and a toxicity control. Each group contained three replicate test chambers. The blank control was used to measure the background CO2production of the inoculum and was not dosed with a carbon source. The reference chambers were dosed with sodium benzoate, a substance known to be biodegradable, at a nominal concentration of 10 mg C/L. The treatment group test chambers were used to evaluate EXP1505385 at a nominal concentration of approximately 10 mg C/L. The toxicity control was used to evaluate toxicity of the test substance to the inoculum and was dosed with both the reference and test substances at nominal concentrations of approximately 10 mg C/L each. The results indicated that the activated sludge inoculum was active, degrading the reference substance 91.9% and that the test substance was not inhibitory to the inoculum at the concentration tested, as the toxicity control exceeded 25% degradation by Day 14 of the study. The average cumulative percent biodegradation for EXP1505385 was 10.7%.

 

 

 

Test Substance

Average

Cumulative Percent

Biodegradation1

Average

Final

pH1

Readily

Biodegradable2

 

EXP1505385

 

 

10.7

 

7.5

No

1     Average of three replicates.

2     Meets or exceeds the OECD criteria for ready biodegradability (60% of TCO2within a 10-day window of reaching 10% TCO2).

Description of key information

A study was performed on the registered substance. It was found not to be readily biodegradable with a biodegradation of 10.7% after 28 days according to the OECD guideline 301B.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

Evidence of ready biodegradability in a Carbon Dioxide Evolution Test is 60% TCO2 within the 28-day test period. In addition, the pass level must be reached within 10 days of achieving 10% TCO2. The final mean percent biodegradation for the substancewas 10.7% after 28 days. The Substnace may not be considered readily biodegradable, since 60% TCO2 was not achieved. The toxicity control achieved > 25% degradation by Day 14 and may be considered non-inhibitory at the concentration tested in this study.