Fatty acids, C16-18, isononyl esters

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Reference 1

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:

Refer to read across justification provided in IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 100 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: CAS 85049-37-2, Oleon, 1995, activated sludge

Conclusions:

No acute toxic effects on microorganisms were found up to the limit of water solubility (OECD 209, activated sludge, RA CAS 85049-37-2).

Reference 2

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

03 Jul 1995

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Each test solution was prepared by dissolving a certain amount of test substance in a mixture of 16 mL of the synthetic sewage and 200 mL of mixed liquor. The mixture was then diluted to 500 mL with deionised water.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Laboratory culture: no, activated sludge was obtained from the waste water treatment plant of Bocholt /Germany), which predominantly treats domestic sewage.
- Preparation of inoculum for exposure: The sludge was sieved through 0.5 mm sieve in order to remove large particles. A small amount of the mixed liquor is dried and weighed. From this result, a calculated amount of mixed liquor was suspended in water to obtain an activated sludge with mixed liquor suspended solids level of 4 g/L
- Initial biomass concentration: 1.6 g/L in test solution

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

20.0 - 20.3 °C

pH:

Test end: 7.71-7.83

Nominal and measured concentrations:

Nominal: 6.5, 13.7, 26.0, 50.1 and 100.2 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: beakers
- Material: borosilicate glass; Size: 1000 mL; Fill volume: 500 mL
- Aeration: constant supply with clean, oil-free air
- No. of vessels per concentration: 1
- No. of vessels per control: 2

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: aerated tap water

EFFECT PARAMETERS MEASURED : Respiration rate inhibition was recorded after 3 h test duration.

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

- No inhibition of the respiration rate was observed at the highest test concentration of 102 mg/L. Instead, a 16.2% stimulation was observed.
- Effect concentrations exceeding solubility of substance in test medium.
- The two control respiration rates are within 15% of each other.

Results with reference substance (positive control):

- Results with reference substance valid? yes
- Relevant effect levels: EC50(3h) is in the range of 5 to 30 mg/L (21.7 mg/L)

Reported statistics and error estimates:

Logit model of Chou and Chou (1985), determining the median effect

Table 1: Respiration rates of activated sludge in control and % inhibition at different test concentrations:

Test substance [mg/L]	Respiration rate [mg O2/L*h]	Inhibition [%]
Control 1	18.02
Control 2	17.09
6.5	19.91	- 13.4
13.7	21.54	- 22.7
26	19.49	- 11.0
50.1	21.89	- 24.7
100.2	20.39	- 16.2

Description of key information

No effects up to the limit of water solubility (OECD 209, activated sludge); read-across

Additional information

There is no study available assessing the toxicity of the target substance Fatty acids, C16-18, isononyl esters (CAS 91031-57-1) to microorganisms. Therefore, read-across to the structurally related source substance Fatty acids, C16-18 and C18-unsatd., 2-ethylhexyl esters (CAS 85049-37-2) was conducted in accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5. The source substance is considered a suitable representative for the assessment of the toxicity of the target substance to microorganisms. A detailed read-across justification is provided in IUCLID section 13.

In the available study, the acute toxicity of Fatty acids, C16-18 and C18-unsatd., 2-ethylhexyl esters on activated sludge was tested according to OECD 209 under GLP conditions. After an incubation time of 3 hours, no inhibition of the respiration rate was observed within the tested concentration range of 6.5 to 100.2 mg/L (nominal), resulting in an EC50(3h) value of >100 mg/L.

Based on the structural and chemical similarity of the target and source substance, the target substance is expected to exhibit a similar ecotoxicological profile. Therefore, it can be concluded that Fatty acids, C16-18, isononyl esters (CAS 91031-57-1) will not exhibit toxic effects to microorganisms up to the limit of water solubility.