Alcohols, C16-18 and C18-unsatd., ethoxylated, sulfates, sodium salts

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

Study period:

04 - 08 Nov 2015

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

Version / remarks:

(2010)

Qualifier:

according to guideline

Guideline:

EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: test substance was warmed up in a water bath at 39.6 °C. Container was then shaken. Direct addition by initial weight into the test flasks followed.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Source: municipal wastewater treatment plant of Mannheim, Germany
- Preparation of inoculum for exposure: after arrival of the activated sludge suspension in the test facility the suspension was sieved with a fine woven mesh (mesh size about 1 mm). Suspension was pre-aerated over night at room temperature. At the next day sludge suspension was washed once with drinking water and adjusted to 3 g/L dw
- Initial biomass concentration: 1.5 g/L dw

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

21.2 - 21.5 °C

pH:

7.4 - 7.5 (initial pH)
7.9 - 8.0 (pH at the end)

Dissolved oxygen:

7.2 - 8.0 mg/L (test start)

Nominal and measured concentrations:

0 (control), 182, 364, 729, 1458, 2915 mg/L (nominal test concentrations)
0 (control), 62.5, 125, 250, 500 and 1000 mg/L (a.i.)

Details on test conditions:

TEST SYSTEM
- Test vessel: 1 L glas beakers
- Fill volume: 500 mL (16 mL 100-fold concentrated synthetic medium with either test substance or reference substance + 234 mL deionized water + 250 mL inoculum suspension)
- Aeration: after preparation of the vessels incubation started by aeration of the vessels with pressured air
- Sludge concentration: 1.5 g/L dw
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6
- No. of vessels per positive control (replicates): 2

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: according to guideline
- Intervals of water quality measurement: temperature was measured 8 times during the incubation in a separate test vessel with deionized water

EFFECT PARAMETERS MEASURED: oxygen uptake was measured for a period of about 8 to 10 min. Due to foaming of the test substance solution in the test vessel during aeration, 25 μL of triisobutyl sulfate was added in all test vessels as antifoam agent

Reference substance (positive control):

yes

Remarks:

3,5 dichlorophenol (1, 10, 100 mg/L)

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 2 915 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

other: EC20

Effect conc.:

140 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

other: EC20

Effect conc.:

410 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Results with reference substance (positive control):

- Results with reference substance valid: yes
- Relevant effect levels: EC50 = 3.5 mg/L

Reported statistics and error estimates:

O2 consumption rates were used for the determination of the ECx by the probit method with the software TOXRAT Professional 2.10.

EC80 > 1000 mg/L based on active ingredient (2915 mg/L based on nominal effect concentration)

Due to technical problems the measured values of the oxygen consumption after 3 hours of incubation of blank control 2 were lost.

Table 1: Validity criteria for OECD 209

Criterion from the guideline	Outcome	Validity criterion fulfilled
The blank controls (without the test substance or reference substance) oxygen uptake rate should not be less than 20 mg oxygen per one gram of activated sludge (dry weight of suspended solids) in an hour.	20 mg/g*h	yes
The coefficient of variation of oxygen uptake rate in control replicates should not be more than 30% at the end of definitive test.	14.1%	yes
The EC50 of 3,5-dichlorophenol should be in the range of 2-25 mg/L	3.5 mg/L	yes

 

Validity criteria fulfilled:

yes

Remarks:

Please refer to tabe 1 at "Any other information on results incl. tables"

Description of key information

One study investigating the toxicity ofAlcohols, C16-18 and C18-unsatd., ethoxylated, sulfates, sodium saltsto activated sludge microorganisms is available. The study was performed according to OECD guideline 209 (GLP) using activated sludge from a municipal wastewater treatment plant. The respiration inhibition of the microorganisms at five different item concentrations (62.5, 125, 250, 500 and 1000 mg/L a.i.) was measered for three hours. An EC50 (3h) > 1000 mg/L a.i. (nominal) was determined.

Additional information

The toxicity of the alkyl ether sulfates (AES) substances to microorganisms was assessed by read-across based on the grouping of substances (category approach). All data on toxicity to microorganisms available for the category were used to assess the toxicity of category substances to microorganisms. The available data indicate no adverse effects of alkyl ether sulfates on microbial activity. All substances of the alkyl ether sulfates category are considered readily biodegradable. In the available screening studies including 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 alkyl ether sulfates.