Hexadecyl palmitate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

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:

Please refer to the analogue justification provided in IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Parameter:

% degradation (O2 consumption)

Value:

75.3

Sampling time:

28 d

Remarks on result:

other:

Remarks:

Source: CAS 17671-27-1, METI, 1992

Parameter:

% degradation (test mat. analysis)

Value:

86

Sampling time:

28 d

Remarks on result:

other:

Remarks:

Source: CAS 17671-27-1, METI, 1992

Details on results:

No 10-day window required. Substance was readily biodegradable.

Validity criteria fulfilled:

no

Remarks:

Biodegradation in one replicate differed by more then 20%.

Interpretation of results:

readily biodegradable

Conclusions:

The substance is readily biodegradable (75.3% BOD in 28 d, OECD 301 C).

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

22 Oct - 19 Nov 1991

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

GLP-Guideline study with acceptable restrictions (The degradation in one replicate was below the pass level and differed by > 20%. However, the mean biodegradation based on BOD was > 70% (replicate 1: 88.5%; replicate 2: 51.56%; replicate 3: 84.79%). Moreover, the primary degradation measured by HPLC was 83, 74 and 100% in the three test vessels supports the assumption that the substance is readily biodegradable according to the OECD criteria. Therefore, the study is considered to be valid.

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

pH was not measured at the end of the study

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 freshwater from rivers and lakes, marine water and marine sediment

Details on inoculum:

- Source of inoculum/activated sludge: 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 solution (pH adapted to 7.0 with NaOH) containing 0.1% 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 appearance and general condition of sludge, determined sediments, pH, temperature and dissolved oxygen and observed with a light microscope, if it is normal.
- Storage length: started to use: 15 Oct 1991
- Concentration of sludge: 3900 mg/L

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Parameter followed for biodegradation estimation:

DOC removal

Parameter followed for biodegradation estimation:

test mat. analysis

Details on study design:

TEST CONDITIONS
- Composition of medium: recommended medium in the guideline
- Test temperature: 25 ± 1 °C
- Suspended solids concentration: 30 mg/L

TEST SYSTEM
- Culturing apparatus: closed oxygen consumption measuring machine with 300 mL culture bottle
- Number of culture flasks/concentration: 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

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, 1 bottle
- Abiotic sterile control: no
- Toxicity control: no

Reference substance:

aniline

Parameter:

% degradation (O2 consumption)

Value:

75.3

Sampling time:

28 d

Parameter:

% degradation (test mat. analysis)

Value:

86

Sampling time:

28 d

Details on results:

No 10-day window required. Substance was readily biodegradable.

Results with reference substance:

The oxygen consumption for aniline in the above used test system reached 60% and 72% degradation after 7 days and 14 days.

The degradation in one replicate was below the pass level (51.56%). However, the mean biodegradation based on BOD was > 70%. Moreover, the primary degradation measured by HPLC was 83, 74 and 100% in the three test vessels supports the assumption that the substance is readily biodegradable according to the OECD criteria.

Table 1. Result of BOD, DOC and HPLC after 28 days

		water + test sub.	sludge + test sub.			Theoretical Amount
		sample No. 6	sample No. 3	sample No. 4	sample No. 5
BOD (*1)	mg	0.0	85.0	49.5	81.4	96.0
DOC	mg	0.0	1.1	0.5	1.0	24.4
HPLC	mg	30.2	5.0	7.7	0.0	30
	% (*2)	101	17	26	0	-

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

(*2) Residue percentage was calculated as followed.

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

Validity criteria fulfilled:

no

Remarks:

Biodegradation in one replicate differed by more then 20%.

Interpretation of results:

readily biodegradable

Description of key information

Readily biodegradable: 75.3% BOD after 28 d (OECD 301 C); read-across

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

There is no study available assessing the ready biodegradability of the target substance hexadecyl palmitate (CAS 540-10-3). Therefore, a read-across to the structurally related source substance docosyl docosanoate (CAS 17671-27-1) was conducted in accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5. The target substance is an ester derived from a fatty acid and fatty alcohol of a carbon chain length of C16 each. The source substance is an ester characterized by a similar fatty acid and fatty alcohol chain length of C22 each and is therefore considered a suitable representative for the assessment of the ready biodegradability of the target substance. A detailed read-across justification is provided in in the analogue justification in IUCLID section 13.

The study with the source substance docosyl docosanoate (CAS 17671-27-1) was performed according to OECD guideline 301 C and GLP. A nominal concentration of 100 mg/L test item was inoculated with a mixture of activated sludge (30 mg/L) from ten sites including four STPs, three rivers, one lake and two bays for 28 d under aerobic conditions (Ministry of Economy, Trade and Industry, Japan, 1992). Biodegradation was followed by continuously measuring O2 consumption, as well as by measuring DOC removal and by the chemical analysis of test item concentrations at regular intervals by HPLC.

After 28 d, a biodegradation of 75.3% (BOD) was observed. Since the substance reached the pass level for OECD 301 C (> 60% after 28 d, no 10-day window required) docosyl docosanoate is readily biodegradable according to the OECD criteria.

Based on the physico-chemical similarities between the target and source substances, it can be concluded that the target substance hexadecyl palmitate (CAS 540-10-3) is readily biodegradable according to the guideline criteria.