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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:
22-Aug-1994 to 23-Sep-1994
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: This study was given a reliability of 1, because it followed an OECD standard guideline, which describes a procedure specifically designed to evaluate this endpoint, and the results were reviewed for reliability and assessed as valid.
Justification for type of information:
A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.
Reason / purpose:
read-across: supporting information
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Inoculum used as the source of the microorganisms was an aliquot of fresh activated sludge from a domestic wastewater treatment facility in New Jersey, USA.
Duration of test (contact time):
28 d
Initial conc.:
ca. 35 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Activated sludge and test medium were combined prior to test substance addition. Test medium consisted of glass-distilled water and mineral salts (Phosphate buffer, Ferric chloride, Magnesium sulfate, Calcium chloride). Test vessels were 1L glass flasks located in a waterbath and electronically monitored for oxygen consumption. Test temperature was 21 +/- 1 Deg C. All test vessels were stirred constantly for 28 days using magnetic stir bars and plates.

Test material was tested in triplicate, controls and blanks were tested in duplicate. The amount of oxygen consumed by microorganisms from the oxidation of the test material was continuously monitored by an automated respirometer during the 28-day test period. Test material concentration was 35mg/L. Sodium benzoate (positive control) concentration was 50mg/L. All test vessels were stirred constantly for 28 days using magnetic stir bars and plates.
Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (O2 consumption)
Value:
15.4
Sampling time:
4 d
Parameter:
% degradation (O2 consumption)
Value:
50.4
Sampling time:
11 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
60.7
St. dev.:
2.77
Sampling time:
28 d
Details on results:
Test material was readily biodegradable, but failed the 10-day window. The biodegradation half-life was <2 weeks. On day 28, 60.7% degradation of the test substance was observed. 10% biodegradation was achieved on approximately day 4, 50% on approximately day 11, and 60% on day 27. By day 3, >60% biodegradation of the positive control was observed. No excursions from the protocol were noted.

The study was extended to Day 31, where the test substance achieved a mean percent biodegradation of 61.5%.
Results with reference substance:
Sodium benzoate, the positive control, achieved 99.0% degradation after 14 days, and therefore this test may be considered valid. On Day 28 of the study, the mean percent degradation of the positive control was 88.7%.

Biodegradation was based on oxygen consumption and the theoretical oxygen demand of the test material as calculated using results of an elemental analysis of the test material.

 

 

% Degradation*

Mean % Degradation

Sample

(day 28)

(day 28)

Test Material

66.8, 56.2, 59.1

60.7

Na Benzoate

89.9, 87.5

88.7

 

* replicate data

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable, but failing 10-day window
Conclusions:
Hydrocarbons, C14 -C18, n-alkanes, isoalkanes, cyclics, aromatics (2 -30%), a multi-component substance, biodegraded to an extent of 61% after 28 days. The data support characterizing the test substance as rapidly biodegradable, readily biodegradable, not expected to persist in the environment under aerobic conditions. Although it did not meet the 10 -day window requirement, it is characterized as readily biodegradable because the criteria is not applied to multi-component substances when assessing their ready biodegradability.
Executive summary:

Hydrocarbons, C14 -C18, n-alkanes, isoalkanes, cyclics, aromatics (2 -30%), a multi-component substance, biodegraded to an extent of 61% after 28 days. The data support characterizing the test substance as rapidly biodegradable, readily biodegradable, not expected to persist in the environment under aerobic conditions. Although it did not meet the 10 -day window requirement, it is characterized as readily biodegradable because the criteria is not applied to multi-component substances when assessing their ready biodegradability.

Description of key information

C14-C20 Aliphatics (2-30% Aromatics), multi-component substances, biodegraded to an extent of 61% after 28 days in an OECD 301F study. The data support characterizing the test substance (Hydrocarbons, C14 -C18, n-alkanes, isoalkanes, cyclics, aromatics (2 -30%)) as rapidly biodegradable, readily biodegradable, not expected to persist in the environment under aerobic conditions. Although it did not meet the 10 -day window requirement, it is characterized as readily biodegradable because the criteria is not applied to multi-component substances when assessing their ready biodegradability.

Key value for chemical safety assessment

Additional information

C14-C20 Aliphatics (2-30% Aromatics), multi-component substances, biodegraded to an extent of 61% after 28 days in an OECD 301F study. The data support characterizing the test substance (Hydrocarbons, C14 -C18, n-alkanes, isoalkanes, cyclics, aromatics (2 -30%)) as rapidly biodegradable, readily biodegradable, not expected to persist in the environment under aerobic conditions. Although it did not meet the 10 -day window requirement, it is characterized as readily biodegradable because the criteria is not applied to multi-component substances when assessing their ready biodegradability.