Hydrocarbons, C11-14, n-alkanes, isoalkanes, <2% aromatics

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

April to May 1997

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

The study was conducted according to a standard guideline without deviations from the protocol, and was conducted under GLP guidelines.

Qualifier:

according to guideline

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:

An un-acclimated activated sludge inoculum was used in this study. The inoculum was obtained from the Chester Sewage Works, Welch Water, Cheshire, UK. The treatment plant receives predominantly domestic sewage. The sludge was collected the day before test initiation. It was prepared for the test by homogenizing it for two minutes after which it was allowed to settle and the supernatant coarse-filtered through medical gauze. The supernatant was added at a 1% loading volume to the test medium and aerated with moist air at the test temperature for approximately 25 hours. Test medium consisted of glass distilled water and mineral salts (phosphate buffer, ferric chloride, magnesium sulfate, calcium chloride). 500 ml of test medium and activated sludge was added to each respirometer flask.

Duration of test (contact time):

28 d

Initial conc.:

98 mg/L

Based on:

ThOD/L

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

Triplicate test systems were used to evaluate the biodegradability of the test substance and duplicate test systems were used to evaluate the biodegradability of the positive control substance at mean concentrations of 98 and 100 mg/L as ThOD, respectively. Blank test systems, which did not contain the test or positive control substance, were run concurrently in triplicate. The test substance was added to the test systems with a syringe and injected into the test medium below the surface. The test system was sealed immediately after addition of the test substance. An aliquot of the positive control stock solution was added to the appropriate test flasks. All test vessels were stirred constantly using magnetic stir bars and plates. The test systems temperature range was 20.2 – 20.3°C.

Reference substance:

benzoic acid, sodium salt

Preliminary study:

A preliminary study was not conducted.

Test performance:

No deviations from the protocol occurred that affected the integrity of the study data.

Parameter:

% degradation (O2 consumption)

Value:

ca. 5

Sampling time:

3 d

Parameter:

% degradation (O2 consumption)

Value:

ca. 34

Sampling time:

4 d

Parameter:

% degradation (O2 consumption)

Value:

ca. 50

Sampling time:

15 d

Parameter:

% degradation (O2 consumption)

Value:

ca. 61

Sampling time:

23 d

Parameter:

% degradation (O2 consumption)

Value:

69

St. dev.:

11

Sampling time:

28 d

Details on results:

The test substance exhibited rapid biodegradation and was assessed as readily biodegradable. The half-life was approximately 15 days. By Day 28, the average percent biodegradation of the test substance was 69%. The test substance reached 10% biodegradation on approximately Day 4 and 60% biodegradation on approximately Day 23.

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

Results with reference substance:

The reference substance biodegraded to an extent of approximately 100% after 28 days. By Day 3, >60% biodegradation of the positive control was observed, which meets the guideline requirement.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable, but failing 10-day window

Conclusions:

The test substance, a multi-component substance, biodegraded to an extent of 69% 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 criterium is not applied to multi-component substances when assessing their ready biodegradability.

Executive summary:

The test substance, a multi-component substance, biodegraded to an extent of 69% 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 criterium is not applied to multi-component substances when assessing their ready biodegradability.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

The registration substance Hydrocarbons, C11-C14, n-alkanes, isoalkanes, <2% aromatics, EC number 701-280-3 (target) and the test substance Hydrocarbons, C11-C14, n-alkanes, isoalkanes, cyclics, <2% aromatics (source) are both hydrocarbons with many constituents in common.
The source substance covers the carbon number range of the target substance. The substances therefore have qualitatively similar properties (RAAF Scenario 2 applies)

Reason / purpose for cross-reference:

read-across source

Parameter:

% degradation (O2 consumption)

Value:

69

Sampling time:

28 d

Description of key information

No ready biodegradadation test data are available for the registered substance Hydrocarbons, C11-C14 n-alkanes, isoalkanes, <2% aromatics, however, measured data are available for a substance with the same carbon range as the registered substance.

 

Hydrocarbons, C11-C14, n-alkanes, isoalkanes, cyclics, <2% aromatics, biodegraded to an extent of 69% after 28 days. This study is considered to be reliable and the data are used as read-across data for the registered substance, Hydrocarbons, C11-C14 n-alkanes, isoalkanes, <2% aromatics.

Additional information

No ready biodegradation test data are available for the registered substance Hydrocarbons, C11-C14 n-alkanes, isoalkanes, <2% aromatics, however, measured data are available for a substance with the same carbon range as the registered substance.

Hydrocarbons, C11-C14, n-alkanes, isoalkanes, cyclics, <2% aromatics biodegraded to an extent of 69% after 28 days in a study conducted according to OECD Technical Guideline 301 F and in compliance with GLP. The data support characterizing Hydrocarbons, C11-C14, n-alkanes, isoalkanes, cyclics, <2% aromatics as rapidly biodegradable, readily biodegradable, not expected to persist in the environment under aerobic conditions. The 10-day window criterion is not applicable for complex substances where sequential degradation of the constituents takes place (REACH guidance R.7b ECHA, 2017). The substance was therefore concluded to be readily biodegradable. The results from this study are considered to be reliable and the data are read across to the registered substance, Hydrocarbons, C11-C14 n-alkanes, isoalkanes, <2% aromatics.

 Supporting data are available for other analogue substances: 

Hydrocarbons, C11-C12, n-alkanes, <2% aromatics biodegraded to an extent of approximately 77% after 28 days. The data support characterizing Hydrocarbons, C11-C12, n-alkanes, <2% aromatics as rapidly biodegradable (readily biodegradable).  

Hydrocarbons, C13-C14, n-alkanes, <2% aromatics biodegraded to an extent of approximately 79% after 28 days. The data support characterizing Hydrocarbons, C13-C14, n-alkanes, <2% aromatics as rapidly biodegradable (readily biodegradable).