Alcohols, C16-18 and C18-unsatd., ethoxylated

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

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.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

other: OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: 20 mg/L test item and 35 mg/L reference item were added directly to the test medium.

Test organisms (species):

activated sludge

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): sewage plant at Hildesheim which comprises mostly municipal sewage and hardly industrial chemical waste.
- Pretreatment: The activated sludge was maintained in an aerobic condition by aeration for four hours and then homogenized with a mixer. The sludge was filtered and the fitrate (30 mL) was subsequently used to initiate inoculum.
- Initial cell/biomass concentration: Colony forming units in the test vessels: 10 exp 5 - 10 exp 6 CFU/L

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

14 d

Test temperature:

20 - 24 °C

Nominal and measured concentrations:

Nominal test substance concentration: 20 mg/L

Details on test conditions:

EST CONDITIONS
- Composition of medium: Mineral nutrient solution according to OECD 301 B
- Test temperature: 20 - 24 °C
- pH: 7.59 - 7.93


TEST SYSTEM
- Culturing apparatus: 5000 mL test vessels (brown glass) filled with 3000 mL test medium
- Number of culture flasks/concentration: 2 - test item, 1 - toxic control, 2 - control


SAMPLING
- Sampling frequency: day 1, 4, 6, 8, 11, 14, 18, 21, 25, 28 and 29

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2 replicates
- Reference control: 1 replicate
- Toxicity control: 1 replicate

Reference substance (positive control):

yes

Remarks:

acetic 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: CO2 evolution

Remarks:

Result of toxicity control from ready biodegradability test

Details on results:

The toxicity control reached 73% biodegradation after 14 days and 87% after 28 days.

Results with reference substance (positive control):

“The reference material attained 87% degradation after 28 days

“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)

The degradation rate determined in the toxicity control was 73% aftter 14 days and thus the test 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

The assessment of the toxicity of the target substance to microorganisms is based on the results of the toxicity control of the available biodegradation study. A NOEC(14 d): 20 mg/L (based on toxicity control of OECD 301 B) is used as key value for the CSA of the target substance .  

Additional information

The toxicity of the Ethoxylates (AE) category substances to microorganisms was assessed by read-across based on the grouping of substances (category approach). The available data were used for a general assessment of the toxicity of the Alcohol Ethoxylates (AE) category substances to microorganisms. Based on the available data adverse effects on microbial activity are not expected. The substances of the Alcohol Ethoxylates (AE) category are readily biodegradable. In all studies conducted with a toxicity control, no inhibition of the degradation process by the test substance was observed. The available studies investigating the respiration inhibition of activated sludge organisms and Pseudomonas putida determined no detrimental effects of the tested Alcohol Ethoxylates.