Isotridecanol, ethoxylated

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:

guideline study with acceptable restrictions

Remarks:

Data based on the inhibition control of a ready biodegradability study

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

according to guideline

Guideline:

other: OECD Guideline 301 B (Ready Biodegradability: CO2-evolution test

GLP compliance:

no

Remarks:

The test facility is certified according to GLP, the performance of the study occurred under GLP-near conditions without the formal procedure of GLP quality assurance.

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

activated sludge, domestic

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Activated sludge from the municipal wastewater treatment plant Breisgauer Bucht, Germany treating predominantly domestic wastewater
- Pretreatment: The activated sludge was washed twice by settling the sludge, decanting the supernatant and resuspending the sludge in aerated tap water
- Concentration of sludge: 30 mg solids/L

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

14 d

Test temperature:

21 - 22 °C

Nominal and measured concentrations:

5.15 ml of a stock solution of 10 g/I reference substance and 43.5 mg of the test item were added to the vessel. This corresponds with a concentration of 40.1 mg/I organic carbon.

Details on test conditions:

TEST CONDITIONS
- Composition of medium: acc. to guideline
- Test temperature: 21.0 - 21.5 QC
- Suspended solids concentration: 30 mg/L dry solids
- Continuous darkness: diffuse light

TEST SYSTEM
- Culturing apparatus: Gas wash bottles (2000 ml volume) with lateral connecting pieces for butyl rubber septums were used as reactors. The CO2 produced in the reactors was absorbed in two 250 ml gas wash bottles in series.
- Number of culture flasks/concentration: 3
- Details of trap for CO2 and volatile organics if used: 0.2 M NaOH

SAMPLING
- Sampling frequency: on days 0, 4, 7, 11, 14, 21, and 28

CONTROL AND BLANK SYSTEM
- Inoculum blank: 3 replicates
- Toxicity control: 1 replicate

Reference substance (positive control):

yes

Remarks:

sodium benzoate

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

43.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: CO2 evolution

Remarks:

Result of toxicity control from ready biodegradability test

Details on results:

The degradation in the toxicity control was 68.6% within 14 days and 76.1% within 28 days (after acidification)

The toxicity control attained 68.6% 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 43.5mg/L can be used as NOEC value for the toxicity to aquatic microorganisms.

Validity criteria fulfilled:

not applicable

Description of key information

NOEC (14 d): 43.5 mg/L (toxicity control of OECD 301 B; read-across)

Additional information

Experimental data on the toxicity of Isotridecanol, ethoxylated, < 2.5 EO are not available. The assessment is based on the results of a toxicity control from a biodegradation study on the structurally similar substance Isotridecanol, ethoxylated, (3EO). The degradation rate of toxicity control of a study following OECD 301 B was 68.6% after 14 days.

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 43.5 mg/L can be used as NOEC value for the toxicity to aquatic microorganisms.