[ω-hydroxy-C16 (saturated and unsaturated) and C16 (unsaturated)] fatty acids

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

(Q)SAR

Adequacy of study:

weight of evidence

Study period:

March, 2018

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:

See attached QMRF and QPRF documents.

Qualifier:

equivalent or similar to guideline

Guideline:

other: Use of QSAR models is consistent with ECHA "Guidance on information requirements and chemical safety assessment Chapter R.6: QSARs and grouping of chemicals".

Version / remarks:

QSAR models predict biodegradability similar to OECD guidelines 301 & 310

Deviations:

not applicable

Principles of method if other than guideline:

See attached (Q)SAR model reporting formats. Additional references include:
- Boethling, R.S., Lynch. D.G., Thom, G.C. 2003. Predicting Ready Biodegradability of Premanufacture Notice Chemicals. Environ. Toxicol. Chem. 22:837-844.
- 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.
- Howard, P.H., Hueber, A.E., Boethling, R.S. 1987. Biodegradation data evaluation for structure/biodegradability relations. Environ. Toxicol. Chem. 6:1-10.
- Howard, P.H., Boethling, R.S., Stiteler, W.M., Meylan, W.M., Hueber, A.E., Beauman, J.A., Larosche, M.E. 1992. Predictive model for aerobic biodegradability developed from a file of evaluated biodegradation data. Environ. Toxicol. Chem. 11:593-603.
- 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.

Specific details on test material used for the study:

Biodegredation was predicted using a QSAR model using eight of the UVCB constituents. These eight constituents, along with water, comprise ca. 98% of the quantified composition and ca. 78% of the total UVCB composition.

Key result

Parameter:

probability of ready biodegradability (QSAR/QSPR)

Remarks on result:

readily biodegradable based on QSAR/QSPR prediction

Interpretation of results:

readily biodegradable

Conclusions:

All eight of the UVCB constituents are predicted to demonstrate ready biodegradability by the BIOWIN (Q)SAR model. [ω-hydroxy-C16 (saturated and unsaturated) and C16 (unsaturated)] fatty acids is predicted to be readily biodegradable.

Executive summary:

Biodegradability of [ω-hydroxy-C16 (saturated and unsaturated) and C16 (unsaturated)] fatty acids was predicted using the BIOWIN predictive model on March 15, 2018. All eight of the queried constituents contain only carbon, hydrogen, and oxygen atoms arranged in a defined linear structure. The molecular weight of each constituent is within the range of molecular weights represented in the model training set. The model identified all of the relevant structural fragments present in the UVCB constituents. All of the UVCB constituents queried are considered to be within the applicability domain of the model. These eight constituents, along with water, comprise ca. 98% of the quantified composition and ca. 78% of the total UVCB composition. All eight of the queried constituents are predicted to exhibit Ready Biodegradability. The compounds contain no heavy metals or complex structures (e.g., cyclic or branched) which would reduce confidence in the predicted results. The predictive modeling results are considered appropriate for supporting the weight of evidence to classify the UVCB substance as Readily Biodegradable.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

(Q)SAR

Adequacy of study:

weight of evidence

Study period:

March, 2018

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:

See attached QPRF and QMRF documents.

Qualifier:

equivalent or similar to guideline

Guideline:

other: Use of QSAR models is consistent with ECHA "Guidance on information requirements and chemical safety assessment Chapter R.6: QSARs and grouping of chemicals".

Version / remarks:

QSAR models predict biodegradability according to OECD guidelines 301 (A-F)

Deviations:

not applicable

Principles of method if other than guideline:

See attached (Q)SAR model reporting formats. Additional references include:
- Roberts, G., Myatt, G. J., Johnson, W. P., Cross, K. P., and Blower, P. E. J. (2000) LeadScope: Software for Exploring Large Sets of Screening Data. Chem. Inf. Comput. Sci., 40, 1302-1314.
- SciQSAR (2009) Reference guide: Statistical Analysis and Molecular Descriptors. Included within the SciMatics SciQSAR software.
- Valerio, L. G., Yang, C., Arvidson, K. B., and Kruhlak, N. L. (2010) A structural feature-based computational approach for toxicology predictions. Expert Opin. Drug Metab. Toxicol., 6:4, 505-518.

Specific details on test material used for the study:

Biodegredation was predicted using a QSAR model for seven individual constituents of the UVCB substance. These constituents, along with water, comprise ca. 98% of the quantified constituents and ca. 77% of the total UVCB composition.

Key result

Parameter:

probability of ready biodegradability (QSAR/QSPR)

Remarks on result:

readily biodegradable based on QSAR/QSPR prediction

Interpretation of results:

readily biodegradable

Conclusions:

All seven of the constituents are predicted to demonstrate ready biodegradability by the battery of three (Q)SAR models. [ω-hydroxy-C16 (saturated and unsaturated) and C16 (unsaturated)] fatty acids is determined to be readily biodegradable.

Executive summary:

Biodegradability of [ω-hydroxy-C16 (saturated and unsaturated) and C16 (unsaturated)] fatty acids was predicted using a (Q)SAR model battery developed by the Danish National Food Institute at the Technical University of Denmark. The battery combines the results of three modeling systems (CASE Ultra, Leadscope, and SciQSAR). Ready biodegradability was predicted for seven (7) individual constituents of the UVCB substance. These constituents, along with water, comprise ca. 98% of the quantified constituents and ca. 77% of the total UVCB composition. All seven of the UVCB constituents queried are considered to be within the applicability domain for each of the three model systems. All of the constituents are either organic carboxylic fatty acids commonly found in biological systems or are related compounds with significant structural similarities to the naturally occurring structures. All seven of the queried constituents are predicted to be NEGATIVE for ‘Not Ready Biodegradability’ i.e., all constituents are predicted to be readily biodegradable. The (Q)SAR predictions are sufficiently reliable and relevant to a weight of evidence approach supporting the REACH registration of the new UVCB substance.

Reference 3

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

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

Adequacy of study:

supporting study

Study period:

14 March 2017 to 13 April 2017

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:

version 1992

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Version / remarks:

version 2008

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

- Solubility in water: Not soluble
- Stability in water: Stable

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge: Activated sludge freshly obtained from a municipal sewage treatment plant: 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands, receiving predominantlydomestic sewage.
- Preparation of inoculum for exposure: The freshly obtained sludge was kept under continuous aeration until further treatment. The concentration of suspended solids was determined to be 4.4g/L in the concentrated sludge. Before use, the sludge was allowed to settle (31 minutes) and the supernatant liquid was used as inoculum at the amount of 10 mL/L of mineral medium.

Duration of test (contact time):

28 d

Initial conc.:

ca. 17 mg/L

Based on:

test mat.

Initial conc.:

ca. 44.71 mg/L

Based on:

ThCO2

Initial conc.:

ca. 12 mg/L

Based on:

TOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Medium stock solutions:
A) 8.50 g KH2PO4; 21.75 g K2HPO4; 67.20 g Na2HPO4·12H2O; 0.50 g NH4Cl dissolved in Milli-RO water (Tap-water purified by reverse osmosis and subsequently passed over activated carbon) and made up to 1 litre (pH 7.4 ± 0.2);
B) 22.50 g MgSO4·7H2O dissolved in Milli-RO water and made up to 1 litre;
C) 36.40 g CaCl2·2H2O dissolved in Milli-RO water and made up to 1 litre;
D) 0.25 g FeCl3·6H2O dissolved in Milli-RO water and made up to 1 litre.
- Test medium composition: 1 litre mineral medium contained 10 mL of solution (A), 1 mL of solutions (B) to (D) and Milli-RO water.
- Aeration: Synthetic air, a mixture of oxygen (ca. 20%) and nitrogen (ca. 80%), was sparged through a bottle, containing 0.5 - 1 litre 0.0125 M Ba(OH)2 solution to trap CO2 at a rate of approximately 1-2 bubbles per second (ca. 30-100 mL/min). The final air contained < 1 ppm CO2.
- Additional substrate: No
- Test temperature: Measured continuously in a vessel with Milli-RO water in the same room. The test temperature ranged from 22 to 24 °C throughout the test.
- Test pH: Measured at the start of the test (day 0) and on the penultimate day (day 14 for the positive and toxicity control and day 28 for the inoculum blanks and test item). The pH value was 7.6 at days 0 and 28 and the pH was 7.7 on day 14.
- Continuous darkness: yes

TEST SYSTEM
- Test vessels: 2 litre glass brown colored bottles.
- Preparation of test solutions: The test item was tested in duplicate at a target concentration of 17 mg/L, corresponding to 12 mg TOC/L (calculated from the molecular formula). Since the test item was not sufficiently soluble to allow preparation of an aqueous solution at a concentration of 1 g/L, weighed amounts were added to the 2-litres test bottles containing medium with microbial organisms and mineral components and 10 mL of Milli-RO water was added to each weighing bottle containing the test item. After vigorous mixing (vortex) the resulting suspension was added quantitatively to the test medium. The test solutions were continuously stirred during the test.
- Number of culture flasks/concentration: 2 per test suspension containing test item and inoculum; 2 per inoculum blank containing only inoculum; 1 positive control containing reference item and inoculum; 1 toxicity control containing test item, reference item and inoculum.
- Culturing apparatus: The day before the start of the test (day -1) mineral components, Milli-RO water (ca. 80% of final volume) and inoculum (1% of final volume) were added to each bottle. This mixture was aerated with synthetic air overnight to purge the system of CO2. At the start of the test (day 0), test and reference item were added to the bottles containing the microbial organisms and mineral components. The volumes of suspensions were made up to 2 litres with Milli-RO water, resulting in the mineral medium described before.
- Measuring equipment: Three CO2-absorbers were connected in series to the exit air line of each test bottle. The amount of CO2 produced was determined by titrating any Ba(OH)2 remaining in the scrubbing bottles with 0.05 M standardized HCl (1:20 dilution from 1 M HCl (Titrisol® ampoule), Merck, Darmstadt, Germany). On the penultimate day, the pH of respective test suspensions was measured and 1 mL of concentrated HCl (37%, Merck) was added to the bottles of the inoculum blank and test suspension. The bottles were aerated overnight to drive off CO2 present in the test suspension. The final titration was made on day 15 (positive and toxicity control) and on day 29 (remaining vessels).

SAMPLING
- Sampling frequency: Titrations were made on day 2, 5, 7, 9, 15, 19, 23, 27, and 29. Titrations for the positive and toxicity control were made over a period of at least 14 days.
- Sampling method: Each time the CO2-absorber nearest to the test bottle was removed for titration; each of the remaining two absorbers was moved one position in the direction of the test bottle. A new CO2-absorber was placed at the far end of the series. Phenolphthalein (1% solution in ethanol, Merck) was used as pH-indicator.

CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes
- Abiotic sterile control: No
- Toxicity control: Yes
- Other: Positive control (reference substance).

Test performance:

In the toxicity control, more than 25% biodegradation occurred within 14 days (64%, based on ThCO2). Therefore, the test item was assumed not to inhibit microbial activity.

Key result

Parameter:

% degradation (CO2 evolution)

Value:

82

Sampling time:

28 d

Details on results:

The two replicate test bottles showed mean cumulative biodegradation values of 70% and 94%, respectively (based on 3 measurements). Since the test item is a UVCB, the 10-day window need not be applied. Therefore, the test item can be classified as readily biodegradable.

Results with reference substance:

The reference item sodium acetate, showed a normal biodegradation curve (86% biodegradatiuon on day 14).

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

The test item was biodegraded significantly (70% to 94%) during the test period. Since the test item is a UVCB, the 10-day window need not be applied. The substance was designated readily biodegradable.

Executive summary:

The biodegradation potential of the substance was investigated in a screening study according to OECD TG 301B and in compliance with GLP criteria. The test item was inoculated with activated sludge from a municipal sewage treatment plant receiving predominantly domestic sewage for 28 days under aerobic conditions in the dark. Before use, the sludge was allowed to settle and the supernatant liquid was used as inoculum at the amount of 10 mL/L of mineral medium. The test item concentration was 17 mg/L, corresponding to 12 mg TOC/L (based on the molecular formula). The theoretical CO2 production (ThCO2) of the test item was calculated to be 2.63 mg CO2/mg. A blank control, a positive control (sodium acetate) and a toxicity control were tested in parallel. The test duration for the positive control and toxicity control was 14 days. Since the substance was not sufficiently soluble to allow preparation of an aqueous solution at a concentration of 1 g/L, weighed amounts were added to the 2-litres test bottles containing medium with microbial organisms and mineral components. To this end, 10 mL of Milli-RO water was added to each weighing bottle containing the test item. After vigorous mixing (vortex) the resulting suspension was added quantitatively to the test medium. The test solutions were continuously stirred during the test to ensure optimal contact between the test item and test organisms. The positive control biodegraded 86% within 14 days and the toxicity control showed that the test substance did not inhibit microbial activity. The study was considered to be valid.

The percentage biodegradation as calculated from the CO2 produced in the test bottles compared to the ThCO2 was found to gradually increase during the course of the test. The final percentage biodegradation after 28 days was determined to be 82% (70% and 95% in two replicates). Since the test item is a UVCB, the 10-day window needs not be applied. Based on these findings, the substance was designated readily biodegradable.

Description of key information

Ready biodegradability of [ω-hydroxy-C16 (saturated and unsaturated) and C16 (unsaturated)] fatty acids was predicted using two QSAR models. The BIOWIN v4.11 software was used to predict the probability of rapid aerobic and anaerobic biodegradation of all eight (8) quantified constituents of [ω-hydroxy-C16 (saturated and unsaturated) and C16 (unsaturated)] fatty acids. A battery of predictive models developed by the Danish National Food Institute at the Technical University of Denmark was also used to predict biodegradation of seven (7) UVCB constituents. These constituents, along with water, comprise ca. 98% of the quantified composition and more than ca. 77% of the total UVCB composition. All of the UVCB constituents queried are considered to be within the applicability domain of the models and were predicted to be Readily Biodegradable. The biodegradability of a similar UVCB substance (EC/List number 943-164-7) was assessed according to OECD method 301B (1992) in 2017. In this study, the test substance was designated readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

[ω-hydroxy-C16 (saturated and unsaturated) and C16 (unsaturated)] fatty acids is a UVCB substance of biological origin. The substance is a complex mixture of long-chain fatty acids produced and excreted by an engineered Escherichia coli K-12 organism through an aqueous microbial fermentation process. The substance is predominantly comprised of linear unbranched long-chain organic fatty acids differentiated only by saturation and number of terminal carboxyl or hydroxyl groups. All of the quantified constituents are comprised of only carbon, hydrogen, and oxygen.

 

With respect to biodegradability, a similar UVCB substance (EC/List number 943-164-7) and the [ω-hydroxy-C16 (saturated and unsaturated) and C16 (unsaturated)] fatty acids substance are considered to be within the same category of chemical substances. The two substances are produced by the same E. coli fermentation and have at least 8.5% of their compositions in common. The substances differ only in the extraction solvent used in their manufacture, resulting in esterificaion of some of the fatty acid constituents. The chain lengths of the constituents and their relative ratios within the UVCB composition are otherwise very similar. Therefore, a chemical category approach is adopted as part of a weight of evidence approach to characterize biodegradability. A qualitative read-across approach is employed in using the previous test results to support the ready biodegradability determination predicted by the QSAR models.

The chemical structures of the UVCB constituents, the predictive modeling results, and the test results of a similar UVCB substance provide a sufficient weight of evidence to characterize the substance as readily biodegradable.