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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:
11 January 2018 to 23 April 2018
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:
1992
Deviations:
no
GLP compliance:
yes
Specific details on test material used for the study:
The test substance is listed as Morflex* 560 or Trihexyl 1,2,4-benzenetricarboxylate (CAS # 1528-49-0). The test substance is a liquid with 99.5% purity. The test substance was obtained from the Sponsor and stored at ambient room temperature.
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
Activated sludge was collected from the Easton Wastewater Treatment Facility, Easton, Maryland on January 12, 2018. 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/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 use in the test. Plates were incubated at 20 ± 3°C for approximately 48 hours.
Duration of test (contact time):
40 d
Initial conc.:
14.3 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (CO2 evolution)
Value:
52.9
Sampling time:
28 d
Key result
Parameter:
% degradation (CO2 evolution)
Value:
77.5
Sampling time:
40 d
Results with reference substance:
The results with sodium benzoate were within the normal range for this reference substance.
Validity criteria fulfilled:
yes
Remarks:
IC content < 5% (protocol ≤ 5%); CO2 emitted by controls <40 mg/L (protocol <70 mg/L; diff.replicates 15.1% (protocol ≤20 %); degradation positive control > 60% at 6 d (protocol ≤14 d to achieve >60%); degradation toxicity >25% at 6d (protocol > 25%).
Interpretation of results:
inherently biodegradable
Conclusions:
The test item attained 52.9% biodegradation after 28 days and 77.5% biodegradation after 40 days, failing the 10-d window. Therefore, the substance cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline 301B. However, the substance was shown to exhibit substantial mineralisation and inherent, ultimate biodegradability, and is therefore not expected to be persistent in the environment.

Description of key information

The key study was a CO2 evolution test conducted in accordance with OECD Guideline 301B. The test item attained 52.9% biodegradation after 28 days and 77.5% biodegradation after 40 days, failing the 10-day window. Therefore, the substance cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline 301B. However, the substance was shown to exhibit substantial mineralisation and inherent, ultimate biodegradability, and is therefore not expected to be persistent in the environment.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable
Type of water:
freshwater

Additional information