Docosyl docosanoate

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

activated sludge respiration inhibition testing

Type of information:

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

Adequacy of study:

key study

Study period:

17 Oct 2012

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

GLP - Guideline study, tested with the source substance dodecyl oleate (CAS 36078-10-1). According to the ECHA guidance document “Practical guide 6: How to report read-across and categories (March 2010)”, the reliability was changed from RL1 to RL2 to reflect the fact that this study was conducted on a read-across substance.

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

GLP compliance:

yes (incl. QA statement)

Remarks:

Landesanstalt für Umwelt, Messungen und Naturschutz Baden-Württemberg, Karlsruhe, Germany

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: 586 µl of the test item were added into the test vessels to obtain final concentrations of 1000 mg/L. Three parallel vessels of the test item were prepared.
- Eluate: no
- Differential loading: yes
- Controls: yes, blank control

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Source: Activated sludge from the municipal wastewater treatment plant Staufener Bucht (Germany) was used as test system. The treatment plant clarifies predominantly domestic wastewater of the region of Staufen and has a capacity of 140 000 inhabitant equivalents. Sampling date of activated sludge was 16 Oct 2012.
- Laboratory culture: no
- Preparation of inoculum for exposure: The activated sludge was kept aerated and fed with synthetic sewage (50 mL per litre and day) until use. Dry solids of the activated sludge was determined as 5.3 g/L by weight measurements before and after 3 h drying at 105°C (mean of triplicate measurements). The activated sludge was washed twice by settling the sludge, decanting the supernatant, and re-suspending the sludge in aerated tap water. Before using, the activated sludge was diluted to 3 g/L dry solids with tap water, in order to obtain a final concentration of 1.5 g/L dry solids in the test.
- Initial biomass concentration: 1.5 g/L (dry solids)

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Test temperature:

18 - 20 °C

pH:

7.7

Nominal and measured concentrations:

nominal: blank, 1000 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: BOD bottles
- Fill volume: 500 mL
- Aeration: All vessels were stirred and aerated throughout the contact time with room air at a rate of 0.5 - 1 L/min using a membrane pump.
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: according to guideline (demineralised water)

EFFECT PARAMETERS MEASURED: respiration rate was measured every 15 min to allow a contact time of 3 h

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Results with reference substance (positive control):

- Results with reference substance valid? yes
- Relevant effect levels: EC50 (3 h): 22.48 mg/L. The EC50 was calculated with ToxRat version 2.09 (ToxRat Solutions GmbH, Alsdorf, Germany) by probit analysis using linear max. likelihood regression.

The validity criteria set out in the Guideline are met.

Table 1: Respiration rate of activated sludge after application of the test substance of the definite test.

Vessel	O2 concentration [mg/L]		Consumption rate [mg/(L*h)]	Inhibition [%]
	First measurement	Last measurement
Blank 1	7.77	6.15	38.9
Blank 2	7.50	6.07	34.3
Blank 3	7.88	6.66	29.3
Blank 4	7.44	6.15	31.0
Blank 5	7.80	6.53	30.5
Blank 6	8.59	7.77	19.7
Test item 1	5.22	3.65	37.7	-23
Test item 2	5.85	4.55	31.2	-2
Test item 3	8.09	3.75	32.2	-5

Coefficient of variation of blanks: 0.19

The results of a first test with a concentration of 1000 mg/L showed high negative inhibitions (until -53%) and a relative low start value of oxygen at the beginning of the measurement. Therefore, the aeration of the test was optimized and the test was repeated. The data of the first test are not shown in detail in the report. In the repetition the values of oxygen at the start of measurement were considerably higher and the evaluation showed conclusive results.

Reference 2

Endpoint:

activated sludge respiration inhibition testing

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 analogue justification provided in IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other:

Remarks:

Source: key, source, RA-A, CAS 36078-10-1, Dako, 2012, activated sludge microorganisms

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other:

Remarks:

key, source, RA-A, CAS 36078-10-1, Dako, 2012, activated sludge microorganisms

Description of key information

NOEC (3 h) of ≥ 1000 mg/L for activated sludge microorganisms (OECD 209).

Additional information

Since no studies investigating the toxicity to microorganisms of docosyl docosanoate (CAS 17671-27-1) are available for this endpoint, in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 a read across to the structurally related read-across substance dodecyl oleate (CAS 36078-10-1) was conducted. The read-across substance dodecyl oleate is characterized by a smaller fatty acid chain (C18 unsatd. compared to C22 (target)) and a smaller fatty alcohol chain length (C12 compared to C22 (target)). This read-across is justified in detail in the overall summary (IUCLID section 6.1) and within the analogue justification in IUCLID Section 13. In this case of read-across, the best suited (highest degree of structural similarity, nearest physico-chemical properties) read-across substance was used for the assessment. Nevertheless, as it can be seen in the data matrix of the analogue justification in IUCLID section 13 and the overall summary, all reliable data support the hazard assessment by showing a consistent pattern of results.

The study with the read-across substance dodecyl oleate was performed according to OECD 209 under GLP conditions (Brunswik-Titze, 2012). A limit test with a concentration of 1000 mg/L did not result in inhibition of respiration rate of activated sludge microorganisms (obtained from a sewage treatment plant treating predominantly domestic wastewater). An increase of respiration was observed in all three test vessels. Thus, a NOEC (3 h) of ≥ 1000 mg/L was derived. Furthermore, in an experimental study investigating the biodegradation of docosyl docosanoate it was concluded that the substance is readily biodegradable according to the OECD criteria which supports the assumption that docosyl docosanoate does not negatively affect microorganisms in a sewage treatment plant.

Based on the available result from one structurally related read-across substance (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5) which is characterized by a similar ecotoxicological profile and comparable structure, it can be concluded that docosyl docosanoate (CAS 17671-27-1) will not exhibit effects on activated sludge microorganisms.