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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
29 days
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Version / remarks:
OECD Guidelines for Testing of Chemicals 301B Ready Biodegradability: CO2 Evolution test 1992
Deviations:
no
GLP compliance:
yes
Specific details on test material used for the study:
Identification: ColaLiquid DC-5
Lot/batch number: 53467J16
Homogeneity (supplied): Homogeneous
Homogeneity (observed): Homogeneous
Date of receipt: 12 December 2016
Expiry date: 3/8/2018
Purity/Composition of test substance: CAS Number: 68855-69-6
Cocamide diisopropanolamine 84-88%
Glycerin 5-8%
Free Amine (DIPA) <5%
Chemex reference: ECO161203
Required storage conditions: Ambient (15°C ±10°C)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
Source: Cambridge Sewage Treatment Works, Cowley Road
Date of collection: 21/02/17
Duration of test (contact time):
28 d
Details on study design:
0.0105g of ColaLiquid DC-5 was dissolved in 100 ml deionised water and analysis was performed in triplicate.
Deionised water and bracketing standards (blank, 20ppm and 75ppm TOC std) were also tested (triplicate).
Reference substance:
acetic acid, sodium salt
Key result
Parameter:
% degradation (CO2 evolution)
Value:
39
Sampling time:
9 d
Key result
Parameter:
% degradation (CO2 evolution)
Value:
>= 71 - <= 74
Sampling time:
28 d
Parameter:
% degradation (CO2 evolution)
Value:
84
Sampling time:
29 d

The inoculum blank should not normally produce more than 40mg/l CO2 (10.9mg/l C) for the test to be valid. A value of 39.3mg/l CO2 (10.7mg/l C) was recorded.

The toxicity control shows a drop in the rate of degradation around day 7 (see figure 1), this is most likely due to a drop in airflow through this vessel. The rate of degradation picks up after day 7 following the restoration of flow rate. The toxicity control is only relevant if low degradation is achieved by the test chemical. ColaLiquid DC-5 showed considerable degradation therefore toxicity control data is irrelevant in this study.

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable, but failing 10-day window
Conclusions:
ColaLiquid DC-5 achieved significant biodegradation over the 28 day period with a maximum of 84% recorded on day 29. This exceeds the >60% degradation relative to the ThCO2 value required for a pass. However, the test protocol also requires that a 10-day window is applied to the degradation results (60% degradation to be reached within 10 days of 10% of the theoretical ThCO2). This was not achieved (10% reached around day 5 and 60% achieved around day 19),
therefore ColaLiquid DC-5 failed to achieve a pass according to the guideline.
However, because of the stringency of the test, this does not necessarily mean that the test substance is not biodegradable under environmental conditions, but indicates that more work would be necessary to establish biodegradability.

Description of key information

ColaLiquid DC-5 achieved significant biodegradation over the 28 day period with a maximum of 84% recorded on day 29. This exceeds the >60% degradation relative to the ThCO2 value required for a pass. However, the test protocol also requires that a 10-day window is applied to the degradation results (60% degradation to be reached within 10 days of 10% of the theoretical ThCO2). This was not achieved (10% reached around day 5 and 60% achieved around day 19), therefore ColaLiquid DC-5 failed to achieve a pass according to the guideline

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable but failing 10-day window

Additional information