Octanoic acid, monoester with glycerol

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to microorganisms, other

Remarks:

toxicity control from ready biodegradability study

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Data based on the inhibition control of a ready biodegradability guideline study. This approach is in accordance with the Guidance on information requirements and chemical safety assessment (Chapter R.7b: Endpoint specific guidance, ECHA 2017).

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

other: OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Version / remarks:

July 1992

GLP compliance:

yes (incl. QA statement)

Remarks:

Landesamt für Umwelt Baden-Württemberg, Germany

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: 164 mL of the test item stock solution with 48.1 mg/L and a pH of 7.5 and 21.0 mg of the reference substance were added into the toxicity control vessel (corresponding to a concentration of 200 mg/L* COD).

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Source of inoculum/activated sludge: municipal wastewater treatment plant AZV Breisgauer Bucht (predominantly domestic wastewater), sampling date of activated sludge: 26 July 2022,
- Preparation of inoculum for exposure: The activated sludge was washed twice with tap water by settling the sludge, decanting the supernatant and re-suspending the sludge. The sludge was aerated at ambient temperature until use.
- Concentration of sludge: 30 mg d.s./L
- Dry solids concentration: 4.27 g/L (drying at 105°C for 5 hours)
- Water filtered: no

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

14 d

Remarks on exposure duration:

Overall exposure was 28 d but the inhibition effect is evaluated after 14 d.

Test temperature:

21.3 – 21.5°C

pH:

7.5

Details on test conditions:

TEST CONDITIONS
- Composition of medium: according to the guideline 301 F
- Solubilising agent: none
- Test temperature: 21.3 – 21.5°C throughout the whole study and therefore within the required range of 22 ± 2°C
- pH: 7.5 (at the beginning and termination of test)
- pH adjusted: The pH of the mineral medium was 7.7 and was therefore adjusted to 7.5 with HCl. After preparation of test solutions, no pH adjustment was needed (pH: 7.5)
- Aeration of dilution water: yes, at least half an hour
- Susspended solids concentration: 30 mg d.s./L

TEST SYSTEM
- Culturing apparatus: OxiTop® (WTW / Xylem)
- Method used to create aerobic conditions: inoculum was aerated until use (see details on inoculum and medium/test solutions were prepared under oxic conditions)
- Measuring equipment: Sensomat (AQUALYTIC®)
- Test performed in closed vessels: yes
- Test performed in open system: no
- Details of trap for CO2 if used: bottles were equiped with rubber quiver inserts for NaOH pellets, which absorb the carbon dioxide produced.

SAMPLING
- Sampling frequency and method: Every 112 minutes, the current pressure was measured and stored by each measuring head.
- Sterility check if applicable: not applicable
- Sample storage before analysis: no

CONTROL AND BLANK SYSTEM
- Inoculum blank: 3 replicates (only inoculum)
- Reference substance: 3 replicates (concentration corresponding to 99.8 mg COD/L)
- Toxicity control: 1 replicate (48.1 mg/L test item and 21 mg reference substance corresponding to a concentration of 200 mg/L COD)

Reference substance (positive control):

yes

Remarks:

acetic acid, sodium salt

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

>= 48.1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: BOD measurements and subsequent calculation of chemical oxygen demand

Remarks on result:

other: Result of toxicity control from ready biodegradability test

Details on results:

The degradation of the toxicity control after 14 days was >25%. Therefore, the test item had no inhibitory effect on the inoculum according to the criterion of the guideline OECD 301 F.

Results with reference substance (positive control):

The reference compound sodium acetate reached the pass level of 60% COD within 5 days.

Since more than 25% degradation occurred in the toxicity control after 14 d (48.9 on Day 4 and >80% on Day 12), the substance is with high probability not toxic to aquatic microorganisms. The test item concentration in the toxicity control of 48.1 mg/L can be used as NOEC value for the toxicity to aquatic microorganisms.

Description of key information

NOEC (14 d) ≥ 48.1 mg/L (nominal, toxicity control of OECD 301 F)

Additional information

Since no studies on the toxicity to aquatic microorganisms are available a ready biodegradability study is used to derive a NOEC for the toxicity to aquatic microorganisms. If a compound degrades well in a ready biodegradability test or does not inhibit the degradation of a positive control at a certain concentration, this concentration can be used as a NOEC value. This approach is in accordance with the Guidance on information requirements and chemical safety assessment (Chapter R.7b: Endpoint specific guidance, ECHA 2017).

 

A substance can be assumed to be not inhibitory to aquatic microorganisms, if in the toxicity control of a ready biodegradation test, more than 25% degradation based on oxygen demand (BOD/ThOD) occurred within 14 days (OECD guideline 301). For Octanoic acid, monoester with glycerol (CAS 26402-26-6) a biodegradation test according to the OECD guideline 301 F is available (and GLP). The test includes a toxicity control, which contains 48.1 mg/L of Octanoic acid, monoester with glycerol and 21 mg/L of the reference material acetic acid, sodium salt (corresponding to 199 mg/L COD). The toxicity control attained 48.9% biodegradation on Day 4 and >80% on Day 12 of incubation. Hence, the substance is not considered toxic to aquatic microorganisms in the toxicity control and the test item concentration of 48.1 mg/L (nominal) can be used as NOEC.