Fatty acids, C16-18

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

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:

04 Nov - 02 Dec 1993

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: (National) Guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

other: BODIS Test (nowadays ISO 10708)

Principles of method if other than guideline:

The BODIS-Test aims to determine the ultimate aerobic biodegradability of organic compounds in an aqueous medium. This test method is apparently similar to the “closed bottle test” (OECD 301 D).

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Sewage plant Hochdahl, Germany
- Pretreatment: 30 g activated sludge were incubated for one week at 20 - 25 °C in a bottle with mineral nutrient solution

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

COD

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: 6 g activated sludge in 200 mL nutrient solution and 20 mg COD test substance
- Test temperature: 20 - 25°C
- Aeration of dilution water: oxygen saturated
- The COD is 470 mg O2/g reference substance.

TEST SYSTEM
- Other: closed bottles on a shaker going in rounds

SAMPLING
- Sampling frequency: after 7, 14, 21 and 28 d

Reference substance:

other: sodium acetate

Parameter:

% degradation (O2 consumption)

Value:

ca. 25

Sampling time:

7 d

Parameter:

% degradation (O2 consumption)

Value:

ca. 47

Sampling time:

14 d

Parameter:

% degradation (O2 consumption)

Value:

ca. 58

Sampling time:

21 d

Parameter:

% degradation (O2 consumption)

Value:

ca. 65

Sampling time:

28 d

Details on results:

The avaerage oxidation of the reference substance sodium acetate was 86% at day 28 (n=3). One replicate of the test substance was identified as outlier and therefore excluded.
According to the opinion of the SCIENTIFIC COMMITTEE ON HEALTH AND ENVIRONMENTAL RISKS on “Compatibility of the ISO standard 10708 (biodegradability test method) with the ultimate biodegradability requirements imposed through Annex III of Regulation 648/2004 of Parliament and of the Council”, the BODIS-Test/ISO 10708 shows the same variability and biodegradation results obtained with other OECD screening tests (SCHER, 2005). Since the pass criterion of 60% degradation within 28 days of the ISO 10708 is consistent with those obtained with the OECD ready biodegradability methods palmitic acid can be regarded as readily biodegradable.

Results with reference substance:

The reference substance sodium acetate was degraded by at least 60% after 14 days (71% at day 7). Therefore, the validity criteria for the test was met.

Reference 2

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:

18 Apr - 15 Sep 1989

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: from a municipal sewage treatment plant (Waterschap de Aa) in Schijndel, Netherlands
- Pretreatment: sludge was aerated for 4 h and then left to settle for 3/4 h. Afterwards the supernatant was decanted.

Duration of test (contact time):

28 d

Initial conc.:

10 mg/L

Based on:

test mat.

Initial conc.:

20 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Test temperature: 19.0 - 21.5 °C
- pH: 5.1 - 6.9
- pH adjusted: no
- Aeration of dilution water: with CO2 free air ( 20% oxygen, 80% nitrogen)

TEST SYSTEM
- Culturing apparatus: test substance and medium were filled in 3 L brown-coloured glass bottles
- Number of culture flasks/concentration: 1
- Details of trap for CO2 and volatile organics if used: The CO2 produced in the test bottles reacted with barium hydroxide in a gas scrubbing bottle which was connected to the test bottles. The amount of produced CO2 was determined by titrating the remaining barium hydroxide with 0.05 N HCl with Phenolphthalein as indicator.

SAMPLING
- Sampling frequency: On day 2, 5, 7, 9, 12, 15, 21, 28

CONTROL AND BLANK SYSTEM
- Inoculum blank: 1
- Toxicity control: 1

Reference substance:

other: sodium acetate

Parameter:

% degradation (CO2 evolution)

Value:

72

Sampling time:

28 d

Remarks on result:

other: 10 mg/L

Parameter:

% degradation (CO2 evolution)

Value:

71

Sampling time:

28 d

Remarks on result:

other: 20 mg/L

Details on results:

The critical biodegradability of the test substance of 60% was not reached within the 10 day time window.

Results with reference substance:

The reference substance was degraded to 93.9% after 28 days and over 60% in the 10 day time window. Thus, the test performance is considered valid.

Interpretation of results:

readily biodegradable, but failing 10-day window

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:

26 Mar - 24 Apr 1991

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: Validity criteria for the reference substance was not passed.

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Deviations:

yes

Remarks:

10 day time window for reference substance was not fulfilled

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: municipal sewage treatment plant "waterschap de Aa" in Schijndel, Netherlands
- Pretreatment: sludge was aerated for 4 h and afterwards left to settle for 1/2 h, then the supernatant was decanted. 30 mL of inoculum was added to the test medium/ reference substance/ blank control and aerated for 24 h with CO2-free air.

Duration of test (contact time):

28 d

Initial conc.:

10 mg/L

Based on:

test mat.

Initial conc.:

20 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: actual concentration of the test medium was 29.8 mg prod./ 3L (nominal 10 mg/L) and 59.5 mg/3L (nominal 20 mg/L) and 59.2 mg reference substance/ 3L (nominal 20 mg/L)
- Solubilising agent (type and concentration if used): none, but due to low water solubility the medium with the test substance was continuously stirred thoughout the test.
- Test temperature: 18 - 21.5 °C
- pH: 7.0 in the blank control, 6.2 in the reference substance, 5.8 in 10 mg/L, 5.5 in 20 mg/L
- pH adjusted: no
- Aeration of dilution water: with CO2-free air (80% oxyen and 20% nitrogen)


TEST SYSTEM
- Culturing apparatus: Closed brown glass bottles with test medium connected to scrubbing bottles containing barium hydroxide which absorbed the developing CO2 from the test flasks (precipitation of barium carbonate)
- Number of culture flasks/concentration: 1
- Details of trap for CO2 and volatile organics if used: The produced CO2 was determined by titrating the remaining barium hydroxide with 0.05 N HCl.

SAMPLING
- Sampling frequency: after 2, 5, 7, 9, 12, 16, 21 and 28 d

CONTROL AND BLANK SYSTEM
- Inoculum blank: 1

Reference substance:

other: sodium acetate

Parameter:

% degradation (CO2 evolution)

Value:

93

Sampling time:

28 d

Remarks on result:

other: 10 mg/L

Parameter:

% degradation (CO2 evolution)

Value:

75

Sampling time:

28 d

Remarks on result:

other: 20 mg/L

Details on results:

The degradation of the test substance reached 93 and 75% respectively. The test medium containing 10 mg/L reached the given 60% within the 10 day time window .

Results with reference substance:

The reference substance was degraded to 93.4% after 28 d. The validit criteria that the reference substance has to pass the 60%-degradation level by day 14 was not met, thus the validity criteria was not fulfilled.

Reference 4

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

(Q)SAR

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Scientifically acceptable method

Justification for type of information:

QSAR prediction: migrated from IUCLID 5.6

Principles of method if other than guideline:

EPI Suite 4.0, BioWin v4.10

GLP compliance:

no

Oxygen conditions:

aerobic

Details on results:

Based on BioWin v4.10 the substance degrades fast.

BIOWIN (v4.10) Program Results:

==============================

SMILES : O=C(O)CCCCCCCC=CCCCCCCCC

CHEM  : 9-Octadecenoic acid (Z)-

MOL FOR: C18 H34 O2

MOL WT : 282.47

--------------------------- BIOWIN v4.10 Results ----------------------------

 

  Biowin1 (Linear Model Prediction)   : Biodegrades Fast

  Biowin2 (Non-Linear Model Prediction): Biodegrades Fast

  Biowin3 (Ultimate Biodegradation Timeframe): Weeks

  Biowin4 (Primary Biodegradation Timeframe): Days

  Biowin5 (MITI Linear Model Prediction)   : Biodegrades Fast

  Biowin6 (MITI Non-Linear Model Prediction): Biodegrades Fast

  Biowin7 (Anaerobic Model Prediction): Biodegrades Fast

  Ready Biodegradability Prediction: YES

Interpretation of results:

readily biodegradable

Reference 5

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

(Q)SAR

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Scientifically acceptable method

Justification for type of information:

QSAR prediction: migrated from IUCLID 5.6

Principles of method if other than guideline:

EPI Suite 4.0, BioWin v4.10

GLP compliance:

no

Oxygen conditions:

aerobic

Details on results:

Based on BioWin v4.10 the substance degrades fast.

BIOWIN (v4.10) Program Results:

==============================

SMILES : O=C(O)CCCCCCCCCCCCCCCCC

CHEM  : Octadecanoic acid

MOL FOR: C18 H36 O2

MOL WT : 284.49

--------------------------- BIOWIN v4.10 Results ----------------------------

 

  Biowin1 (Linear Model Prediction)   : Biodegrades Fast

  Biowin2 (Non-Linear Model Prediction): Biodegrades Fast

  Biowin3 (Ultimate Biodegradation Timeframe): Weeks

  Biowin4 (Primary Biodegradation Timeframe): Days

  Biowin5 (MITI Linear Model Prediction)   : Readily Degradable

  Biowin6 (MITI Non-Linear Model Prediction): Readily Degradable

  Biowin7 (Anaerobic Model Prediction): Biodegrades Fast

  Ready Biodegradability Prediction: YES

Interpretation of results:

readily biodegradable

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

No study on ready biodegradability is available for fatty acids, C16–C18. Therefore, read across from the key studies of palmitic acid (C16, saturated), oleic acid (C18, 1 double bond, 9-Octadecenoic acid, (Z)-) and stearic acid, (C18, saturated) was done as well as QSAR predictions on ready biodegradability.

Palmitic acid was tested according to the ISO 10708 (BODIS test) which is apparently similar to the “closed bottle test”, OECD 301 D. Three replicates with palmitic acid at concentrations of 100 mg/L COD were incubated with non-adapted activated sludge. The oxygen consumption was monitored during the 28 day test period. The results clearly showed that palmitic acid was degraded by 65% in average at day 28 (Börner,1994). According to the opinion of the SCIENTIFIC COMMITTEE ON HEALTH AND ENVIRONMENTAL RISKS on “Compatibility of the ISO standard 10708 (biodegradability test method) with the ultimate biodegradability requirements imposed through Annex III of Regulation 648/2004 of Parliament and of the Council”, the BODIS-Test/ISO 10708 shows the same variability and biodegradation results obtained with other OECD screening tests (SCHER, 2005). Since the pass criterion of 60% degradation within 28 days of the ISO 10708 is consistent with those obtained with the OECD ready biodegradability methods, palmitic acid can be regarded as readily biodegradable.

Coenen (1991) conducted a GLP study according to OECD 301B. After 28 days 93% and 75% of oleic acid were biodegraded at concentrations of 10 mg/L and 20 mg/L, respectively und thus passed the 60% degradation level. Furthermore, the degradation value at the lower test concentration of 10 mg/L met the 10-day window. According to the criteria for ready biodegradation oleic acid (9-Octadecenoic acid, (Z)-) is readily biodegradable. Since the reference substance itself failed the pass criterion for validity (60% degradation was not reached within 14 d), the study should had been repeated.

Stearic acid, saturated was tested by Bogers (1989) for ready biodegradability according to OECD 301B and GLP. At concentrations of 10 and 20 mg/L the degradation values were 72% and 71%, respectively at test termination (28 d). The pass criterion for ready biodegradability (60% degradation within 10 days once exceeded 10% degradation) was barely missed. However, the sampling interval was not as narrow as recommended by the OECD guideline (sampling every second day, followed by sampling every fifth day) which might have led to the barely missing of the 10-day window. The failure of the 10-day window in biodegradation tests due to the low water solubility/bioavailability as well as to the inappropriate sampling intervals were 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 the ready biodegradability of the fatty acids. Reliable results of the QSAR model BIOWIN v.4.10 (EPI Suite, 2010) predicts ready biodegradability for stearic acid and oleic acid. This method is based on the application of Bayesian analysis to ready biodegradation data for chemicals, derived collectively from all six OECD301 test methods plus OECD310.

Overall, the fatty acids, C16-C18 is regarded as readily biodegradable. This judgment is consistent with the hazard assessment presented in the OECD SIDS (2009) for the category “Aliphatic Acids Category” where aliphatic fatty acids with a carbon chain length in the range of C8 – C22 were judged to be readily biodegradable.