Fatty acids, C16, C18 and C18-unsaturated, C12-15 alcohol (linear and branched), esters

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

17 Oct 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP Guideline study

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 the 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: RA-A, CAS 36078-10-1, Dako, 2012, activated sludge microorganisms, 3 h

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:

Source: RA-A, CAS 36078-10-1, Dako, 2012, activated sludge microorganisms, 3 h

Conclusions:

The effect concentrations retained for the toxicity to microorganisms is an EC50 (3 h) of > 1000 mg/L (nominal) and a NOEC (3 h) of ≥ 1000 mg/L (nominal), based on an experimental study with a structurally and chemically closely related source substance (OECD 209, activated sludge); read-across

Description of key information

NOEC (3 h) of ≥ 1000 mg/L (OECD 209, activated sludge microorganisms); read-across

Additional information

There is no study available, in which the toxicity of Fatty acids, C16, C18 and C18-unsaturated, C12-15 alcohol (linear and branched), esters to aquatic microorganisms was assessed. Therefore, read-across to the structurally and chemically closely related source substance Dodecyl oleate (CAS 36078-10-1) was performed in accordance with Regulation (EC) No 1907/2006 Annex XI, section 1.5 in order to fulfill the data requirements for this substance. The source substance is characterized by similar fatty acid chain lengths and alcohol components as the target substance and is therefore considered a suitable representative for the assessment of the toxicity of the target substance to aquatic microorganisms. A detailed read-across justification in provided in IUCLID section 13.

The available study with the source substance Dodecyl oleate was conducted according to OECD guideline 209 and in compliance with GLP. In a limit test, 1.5 g/L activated sludge (dry solids) from a domestic sewage treatment plant was exposed to a nominal test item concentration of 1000 mg/L for 3 h. At test end, the respiration rate of the activated sludge microorganisms was not inhibited, resulting in a NOEC (3 h) of ≥ 1000 mg/L. Thus, it is concluded Dodecyl oleate does not cause toxicity to aquatic microorganisms.

 

Based on the high degree of structural and chemical similarity between the target and the selected source substance, the target substance is expected to exhibit a similar ecotoxicological profile as the source substance. Therefore, it can be concluded that the target substance Fatty acids, C16, C18 and C18-unsaturated, C12-15 alcohol (linear and branched), esters does not cause toxic effects to aquatic microorganisms up to its limit of water solubility (< 6.57 µg/L at 20 °C, pH 6.3, OECD 105).