Dodecanoic acid, ester with 1,2,3-propanetriol

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to microorganisms, other

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 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 B (Ready Biodegradability: CO2 Evolution Test)

Qualifier:

according to guideline

Guideline:

other: EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

GLP compliance:

yes (incl. QA statement)

Remarks:

Ministerium für Arbeit, Integration und Soziales des Landes Nordrhein-Westfalen

Test organisms (species):

other: activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Sewage treatment plant Ruhrverband Kläranlage, Schmallenberg, Germany (February 14th, 2017)
- Preparation of inoculum for exposure: The sludge was washed in mineral medium and centrifuged (at 1100 g for 10 minutes). The supernatant was discarded. The concentrated sludge was suspended in mineral medium to a concentration of 2.6 g suspended solids/L. The sludge was aerated with CO2-free air over night to purge the system of carbon dioxide. A sample was withdrawn just before use for the determination of the dry weight of the suspended solids.
- Concentration of sludge: 29 mg dry mass/litre (87 mg dry mass/3 L)

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

14 d

Details on test conditions:

TEST CONDITIONS
- Composition of medium: Mineral medium
- Test temperature: 22 °C (± 2 °C)
- pH: 7.4 of mineral medium
- Aeration of dilution water: with CO2-free air
- Suspended solids concentration: 29 mg/L in the final 3 litres
- Continuous darkness: yes
- Other: To each test vessel 2400 mL mineral medium was added. A volume of 34.3 mL of the prepared activated sludge to give a concentration of suspended solids of 29 mg/L in the final 3 litres of inoculated mixture was added. After aeartion with CO2-free air overnicht, two absorption bottles, each containing 200 mL of 0.05 M sodium hydroxide solution were connected in series to each 5-litre flask. Test item was added on a weight basis. The volume of suspensions in all flasks was filled up to 3 litres by the addition of mineral medium.

TEST SYSTEM
- Culturing apparatus: 5-litre flasks
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: The vessels were aerated by the passage of carbon dioxide free air at a controlled rate during the incubation period.
- Test performed in closed vessels due to significant volatility of test substance: yes
- Details of trap for CO2 and volatile organics if used: The CO2 is trapped in sodium hydroxide and is measured as inorganic carbon.

SAMPLING
- Sampling frequency: Days of sampling for CO2 measurement were day 2, 5, 9, 12, 14, 21, 28, and 29.
- Sampling method: The samples of suspensions (IC measurement) were filtered through ROTH PET filters (0.45 μm) as soon as they are taken. The samples of the hydroxide absorbers were measured without any manipulation to avoid CO2 enrichment.
The measurements of the TIC concentration were carried out using a TC analyser (Shimadzu TOC-V-CPH).
- Sample storage before analysis: Analysis was done directly after sampling.

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2
- Abiotic sterile control: 1
- Toxicity control: 1

Reference substance (positive control):

yes

Remarks:

benzoic acid, sodium salt

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

>= 20 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Result of toxicity control from ready biodegradability test

Results with reference substance (positive control):

In the positive control, 79% was degraded after 14 d confirming the suitability of the inoculum.

The toxicity control attained 84% degradation after 14 days of incubation.

 “If in  a toxicity test, containing both the test and reference substance, less than 35% degradation (based on total DOC) or less than 25% (based on total ThOD or ThCO2) occurred within 14 days, the test substance can be assumed to be inhibitory.” (OECD guideline 301)

Since more than 35% degradation occurred in the toxicity control, the substance is with high probability not toxic to aquatic microorganisms. The test item concentration in the toxicity control of 20 mg/L can be used as NOEC value for the toxicity to aquatic microorganisms.

Description of key information

NOEC (14 d) ≥ 20 mg/L (toxicity control after 14 days incubation)

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

20 mg/L

Additional information

Since no study on the toxicity to activated sludge microorganisms is available a toxicity control from the ready biodegradability study is used to derive a NOEC for the toxicity to activated sludge 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 activated sludge microorganisms, if in the toxicity control of a ready biodegradation test, more than 25% degradation based on CO2 evolution (CO2/ThCO2) occurred within 14 days (OECD guideline 301). For Dodecanoic acid, ester with 1,2,3-propanetriol (CAS 37318-95-9) a biodegradation test according to OECD 301B (GLP) is available. The test includes a toxicity control, which contains 20 mg/L of Dodecanoic acid, ester with 1,2,3-propanetriol and 20 mg/L of the reference material [benzoic acid, sodium salt]. The toxicity control attained 84% degradation after 14 days of incubation. Hence, the substance is not toxic to aquatic microorganisms in the toxicity control and a NOEC (14 d) ≥ 20 mg/L was derived.