Docosanoic acid

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: inherent biodegradability

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

not available

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Well documentated publication

Reason / purpose for cross-reference:

reference to same study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 302 C (Inherent Biodegradability: Modified MITI Test (II))

Deviations:

yes

Remarks:

MITI-I and MITI-II combi study: test was performed in 100 mg/L of test substance and 30 mg/L of inoculum.

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

other: mixture of activated sludge from STP with surface water from rivers, lakes and marine, as well as marine sediment at shores.

Details on inoculum:

- Source of inoculum/activated sludge (location, sampling depth): location: 10 sites (4 sewage plants, 3 rivers, 1 lake and 2 bays) around Japan, sampling depth: return sludge in sewage plants, surface water and surface soil of foreshore
- Laboratory culture: Thirty minutes after stopping of aeration, discard about one third of the whole volume of supernatant and add an equal volume of a mineral medium (pH adapted to 7.0 ± 1.0 with NaOH) containing 5% each of glucose, peptone and pottasium orthophosphate, to the settled material and re-commence aeration. This procedure was repeated once per day.
- Temperature: 25 ± 2 °C
- Storage conditions: observed apperance and general condition of sludge, determined sediments, pH, temperature and dissolved oxygen and observed with a light microscope, if it is normal.
- Preparation of inoculum for exposure: Sample No.1: Test substance in water at 100 mg/L, No.2 - 4: test substance in meneral medium at 100 mg/L, No.5: aniline in mineral medium at 100 mg/L, No.6: mineral medium only
- Storage length: started to use: 15 -07-1997
- Concentration of sludge: 4300 mg/L
- Water filtered: no

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

test mat. analysis

Details on study design:

TEST CONDITIONS
- Suspended solids concentration: 100 mg/L

Parameter:

% degradation (test mat. analysis)

Value:

73

Sampling time:

28 d

Details on results:

See table 1 and 2.

Table 1. Analytical result

		water + test sub.	sludge + test sub.			Theoretical Amount
		sample No. 1	sample No. 2	sample No. 3	sample No. 4
BOD (*1)	mg	0.3	43.0	50.3	47.1	90.3
GC	mg	28.4	9.5	5.6	7.6	30
	% (*2)	95	32	19	25	-

(*1) (sludge + test sub.) was calculated by substracting blank values.

(*2) Residue and production percentage was calculated as followed.

Residue percentage = Residue amount (mg) / Theoretical amount (mg) x 100

Table 2. Degradation rate

	sample No. 2	sample No. 3	sample No. 4	Mean
BOD	48	56	52	52
GC	67	80	73	73

Validity criteria fulfilled:

yes

Interpretation of results:

inherently biodegradable

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

12 Aug - 09 Sep 1997

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP - Guideline study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: Circular on Test Methods of New Chemical Substances (Japan), Biodegradation test

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

other: mixture of activated sludge from STP with surface water from river, lake and marine, as well as marine sediment at shore.

Details on inoculum:

- Source of inoculum/activated sludge (location, sampling depth): location: 10 sites (4 sewage plants, 3 rivers, 1 lake and 2 bays) around Japan, sampling depth: return sludge in sewage plants, surface water and surface soil of foreshore
- Laboratory culture: Thirty minutes after stopping of aeration, discard about one third of the whole volume of supernatant and add an equal volume of a mineral medium (pH adapted to 7.0 ± 1.0 with NaOH) containing 5% each of glucose, peptone and pottasium orthophosphate, to the settled material and re-commence aeration. This procedure was repeated once per day.
- Temperature: 25 ± 2 °C
- Storage conditions: observed apperance and general condition of sludge, determined sediments, pH, temperature and dissolved oxygen and observed with a light microscope, if it is normal.
- Preparation of inoculum for exposure: Sample No.1: Test substance in water at 100 mg/L, No.2 - 4: test substance in meneral medium at 100 mg/L, No.5: aniline in mineral medium at 100 mg/L, No.6: mineral medium only
- Storage length: started to use: 15 -07-1997
- Concentration of sludge: 4300 mg/L
- Water filtered: no

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: Recomended medium in the guideline
- Test temperature: 25 ± 1 °C
- Suspended solids concentration: 30 mg/L
- Continuous darkness: no data

TEST SYSTEM
- Culturing apparatus: closed oxgen consuption measuring machine with 300 mL culture bottle
- Number of culture flasks/concentration: 3
- Method used to create aerobic conditions: 1 (water + test substance), 3 (sludge + test sub.), 1 (sludge + reference sub.), 1 (sludge)
- Measuring equipment: Coulometer
- Details of trap for CO2 and volatile organics if used: soda lime

SAMPLING
- Sampling frequency: Continuously
- Sterility check if applicable: no
- Sample storage before analysis: no data

CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes

STATISTICAL METHODS: not described

Reference substance:

aniline

Parameter:

% degradation (O2 consumption)

Value:

52

Sampling time:

28 d

Remarks on result:

other: BOD/ThOD

Details on results:

See table 1 and 2.

Results with reference substance:

BOD of aniline in the above used test system reached 61.4 mg and 70.5 mg after 7 days and 14 days.

Table 1. Result of BOD (mg) measurement

	7^thday	14^thday	21^stday	28^thday
Sludge + Test substance (Sample No.2)	12.4	22.5	34.1	48.3
Sludge + Test substance (Sample No.3)	18.9	32.3	45.0	55.6
Sludge + Test substance (Sample No.4)	18.0	29.7	39.0	52.4
Water + Test substance (Samle No. 1)	0.1	0.1	0.3	0.3
Control blank (Sample No.6)	2.3	3.8	5.2	5.3
Sludge + Aniline (Sample No.5)	61.4	70.5	71.8	72.0

Table 2. Degradation rate

	sample No. 2	sample No. 3	sample No. 4	Mean
BOD	48	56	52	52

Validity criteria fulfilled:

yes

Interpretation of results:

other: under test conditions not ready biodegradable

Reference 3

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

migrated information: read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Study period:

no data

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

GLP compliance:

no

Remarks:

GLP not yet implemented in lab at time of study, however study adhered to GLP comparable quality conditions.

Oxygen conditions:

aerobic

Inoculum or test system:

other: Garden-mould suspension, not acclimated

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Henkel garden center- Concentration of sludge:
- Initial cell/biomass concentration: 10^3-10^5 cells/ml
- Preparation of inoculum for exposure: 100 g garden mould was added to 1 L tap water and shaken
- Water filtered: yes
- Type and size of filter used, if any: coarse paper, the first 200 ml was discarded

Duration of test (contact time):

30 d

Initial conc.:

2 other: mg/l

Based on:

other: active material

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: deionized water
- pH: 7-8
- Aeration of dilution water: Aerated using compressed air delivered through a sintered glass tube until saturation was reached.

TEST SYSTEM
- Culturing apparatus:
- Number of culture flasks/concentration: 2

SAMPLING
- Sampling frequency: 5, 15, and 30 days

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes


STATISTICAL METHODS: average

Reference substance:

other: dodecylsulfate

Parameter:

% degradation (O2 consumption)

Value:

40

Sampling time:

5 d

Parameter:

% degradation (O2 consumption)

Value:

77

Sampling time:

15 d

Parameter:

% degradation (O2 consumption)

Value:

90

Sampling time:

30 d

Results with reference substance:

57% degraded in 5 days, 89% degraded in 30 days

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

The best-fit biodegradation curve shows progression from 10% to 60%BOD/ThOD in less than 10 days, therefore the substance meets the OECD "readily biodegradable" criterion.

Reference 4

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

(Q)SAR

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

1. SOFTWARE
EPI Suite v4.11 (June 2017) Estimation Programs Interface Suite™ for Microsoft® Windows v 4.11 (June 2017). US EPA, United States Environmental Protection Agency, Washington, DC, USA.

2. MODEL (incl. version number)
BioWin v4.11

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
See “Test material information”

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
See attached information on the model provided by the developer. Further information on the OECD criteria as outlined by the applicant is provided below under "Any other information of materials and methods incl. tables"

5. APPLICABILITY DOMAIN
See attached information and information as provided in "Overall remarks, attachments".

6. ADEQUACY OF THE RESULT
See assessment of adequacy as outlined in the "Overall remarks, attachments" section.

Qualifier:

according to guideline

Guideline:

other: REACH Guidance on QSARs and grouping of chemicals (R.6)

Principles of method if other than guideline:

- Software tool(s) used including version: EPI Suite v4.11 (June 2017)
- Model(s) used: BioWin v4.11
Full reference and details of the used formulas can be found in:
1. Boethling, R.S., Howard, P.H., Meylan, W., Stiteler, W., Beaumann, J., Tirado, N. 1994. Group contribution method for predicting probability and rate of aerobic biodegradation. Environ. Sci. Technol. 28:459-65.
2. Boethling, R.S., Lynch. D.G., Thom, G.C. 2003. Predicting Ready Biodegradability of Premanufacture Notice Chemicals. Environ. Toxicol. Chem. 22:837-844.
3. Boethling, R.S., Lynch, D.G., Jaworska, J.S., Tunkel, J.L., Thom, G.C., Webb, S. 2004. Using BIOWIN, Bayes, and batteries to predict ready biodegradability. Environ. Toxicol. Chem. 23:911-920.
4. Howard, P.H., Boethling, R.S., Stiteler, W.M., Meylan, W.M., Hueber, A.E., Beauman, J.A.1992. Predictive model for aerobic biodegradability developed from a file of evaluated biodegradation data.Environ. Toxicol. Chem.11:593-603.
5. Tunkel, J., Howard, P.H., Boethling, R.S., Stiteler,W., Loonen, H. 2000. Predicting Ready Biodegradability in the Japanese Ministry of International Trade and Industry Test.Environ. Toxicol. Chem.19:2478-2485.
6. Meylan, W., Boethling, R.S., Aronson, D., Howard, P., Tunkel, J. 2007. Chemical structure-based predictive model for methanogenic anaerobic biodegradation potential.Environ. Toxicol. Chem.26:1785-1792.
7. US EPA. 2012. Estimation Programs Interface Suite™ for Microsoft® Windows, v 4.11. United States Environmental Protection Agency, Washington, DC, USA.
- Model description: see field 'Justification for non-standard information', 'Attached justification' and 'any other information on Material and methods'.
- Justification of QSAR prediction: see field 'Justification for type of information', 'Attached justification' and/or 'overall remarks'.

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Remarks on result:

readily biodegradable based on QSAR/QSPR prediction

For detailed information on the results please refer to the attached report.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

Ready and inherent biodegradability of docosanoic acid were tested by the Japanese Ministry for the Environment (MOE, 1997). At a concentration of 100 mg/L the substance biodegrades up to 48 - 56% (BOD) after 28 days according to OECD 301C. In the inherent biodegradation test according to OECD 302C, the substance was tested at a concentration of 30 mg/L resulting in biodegradation rates of docosanoic acid up to 79 - 96% (BOD) after 28 days. The substance docosanoic acid barely failed the ready biodegradability test and was classified according to the OECD SIDS (2001) as inherently biodegradable.

A ready biodegradation of the unsaturated fatty acids with a chain length of was shown in a biodegradation test similar to OECD 301 D (Closed Bottle Test). The read across substance docosenoic acid (C22:1, CAS 112-86-7) was inoculated with suspended garden mould for 30 days. Based on the oxygen consumption biodegradation on day 5, 15 and 30 was 40 %, 77 % and 90 %, respectively. Therefore, it can be concluded, that docosenoic acid, a C22:1 fatty acid, is readily biodegradable.

Results of the QSAR model BIOWIN v.4.11 (EPI Suite, 2022) predict ready biodegradability for docosanoic acid. This method is based on the application of Bayesian analysis to readily biodegradation data for chemicals, derived collectively from all six OECD301 test methods plus OECD310.

The available data indicate that individual degradation rates reported may vary to some degree for fatty acids even of same carbon chain length depending on their physico chemical properties (e. g. water solubility), bioavailability and test methods employed. The failure of some fatty acids to pass the stringent ready biodegradation tests due to the low water solubility and reduced bioavailability was already recognized and discussed within the framework of the SIDS Initial Assessment Report for the Category “Aliphatic Acids” (OECD, 2009) and judged not to preclude a ready biodegradability of the fatty acids.

According to the ECHAs Guidance on information requirements and chemical safety assessment (Chapter R.7b: Endpoint specific guidance, 2008) consistent positive test results should generally supersede negative results.