Alcohols, C16-18 and C18-unsatd., ethoxylated, sulfates, sodium salts

Biodegradation in water: screening tests

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:

12 Jan - 10 Mar 2022

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:

Revised 1992

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): collected from Harrogate South sewage treatment works (North Yorkshire, UK).
- Concentration of sludge: 4.3 g/L.suspended solids

Duration of test (contact time):

28 d

Initial conc.:

15 mg/L

Based on:

TOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: acc. to guideline
- pH: 7.21 - 7.68
- Test temperature: 20.3 – 22.2°C
- Suspended solids concentration: 4.3 g/L.
- Continuous darkness: yes

TEST SYSTEM
- Number of culture flasks/concentration: 2 (2 L Duran bottles)
- Method used to create aerobic conditions: vessels were sparged with a supply of CO2-free air.
- Measuring equipment: (IC) concentration was determined using the Suez TOC analyser system
- Details of trap for CO2 and volatile organics if used: barium hydroxide solution

SAMPLING
- Sampling frequency: day 2, 5, 7, 9, 12, 16, 21, 26, and 28

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, 2 replicates
- Toxicity control: yes, 1 replicate

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (CO2 evolution)

Value:

69

Sampling time:

28 d

Details on results:

The mean total CO2 production in the blank control vessels was 27.45 mg/L on Day 28
Toxicity Control:
The test item was not considered to have an inhibitory effect on the inoculum because the 25% biodegradation level (calculated on total theoretical carbon content of vessel) was achieved in the Toxicity Control (containing the reference substance and the test item) between Day 2 and 5 (Day 2 = 14.7%; Day 5 = 30.5%).

Results with reference substance:

The mean percentage biodegradation of the reference substance was > 60% by Day 7 and at the end of the test (Day 29 - post acidification) the mean percentage biodegradation of the reference substance was 87.3% (vessel 3: 91.1%; vessel 4: 83.4%).

Table 1: Mean degradation rates

	Test item	Reference substance	Toxcity control
Day 2	10.3	28.57	14.72
Day 5	28.59	51.60	30.50
Day 7	43.55	65.92	42.01
Day 9	51.26	72.12	47.87
Day 12	55.92	76.50	51.58
Day 16	58.96	80.16	54.91
Day 21	62.42	84.01	58.42
Day 26	65.90	84.01	61.83
Day 28	67.38	85.94	63.91
Day 29*	68.84	87.27	64.78

*refers to the day that titrations of trap content from acidified vessels were performed.Actual acidification was performed on Day 28.

Table 2: Validity criteria for OECD 301B.

Criterion from the guideline	Outcome	Validity criterion fulfilled
Difference of extremes of replicate values of the removal of the test chemical at the plateau, at the end of the test or at the end of the 10-d window, as appropriate, is less than 20%.	> 20%	yes
Percentage degradation of the reference compound reached the pass level by day 14 (≥ 60%).	76.50 within 12 d	yes
The toxicity control should degrade to at least 35% (based on DOC) or at least 25% (based on ThOD or ThCO2) within 14 d.	51.58% within 14 d	yes
The IC content of the test substance suspension in the mineral medium at the beginning of the test must be less than 5% of the TC.	<5%	yes
The total CO2 evolution in the inoculum blank at the end of the test should not normally exceed 40 mg/L medium.	27.45 mg/L on day 28	yes

 

Validity criteria fulfilled:

yes

Remarks:

Please refer to table 2 at "Any other information on results incl. tables"

Interpretation of results:

readily biodegradable

Description of key information

Readily biodegradable: 87.3% (CO2 evolution) in 28 days (OECD 301B)

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

The assessment is based on the data currently available. New studies, based on the category review and the final decisions issued for some of the category substances, which are also relevant for this assessment, are currently being conducted. The hazard assessment with respect to aquatic toxicity will be updated once all ongoing studies have been finalised.

In a screening study investigating the ready biodegradability of Alcohols, C16-18 and C18-unsatd., ethoxylated, sulfates, sodium salts a degradation rate of 69 % after 28 days was determined. The study was conducted according to OECD 301B using activated sludge from a municipal wastewater treatment plant as incoulum. The degradation rate was determined by measuring the CO2 evolution of the activated sludge organisms during the 28 day incubation period.

Based the results, the substance is considered readily biodegradable according to OECD criteria.