Registration Dossier

Administrative data

Endpoint:
activated sludge respiration inhibition testing
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
1996-12-11
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Sorbitanmonococoat is the C12-C14 C chain homologue of the C8 Sorbitanmonocaprylate. Usually toxicity to microorganisms is higher with longer C chain length. Read-across from Sorbitanmonococoat is most likely a worst case approach. The test follows the OECD 209 Guideline. Raw data are not reported but this procedure was not uncommon at that time.Due to this fact a 'reliable with restrictions' is assigned.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1996
Report Date:
1996

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
no
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Sorbitanmonococoat
- Physical state: Liquid, colourless
- Lot/batch No.: 8/96
- Expiration date of the lot/batch: 1997-10-01
- Storage condition of test material: Room temperature, protected from light, in original container.

Sampling and analysis

Analytical monitoring:
no

Test solutions

Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method:direct weighing
- Eluate: Synthetic waste water according to OECD Guidelinie 209
- Differential loadings: 100 - 320 - 1000 - 3200 - 10000 mg/L
- Controls: Test medium without test or reference item.

Test organisms

Test organisms (species):
activated sludge
Details on inoculum:
- Preparation of inoculum for exposure: Non adapted activated sludge from the sewage plant at Hildesheim (Municipal sewage treatment plant of Hildesheim, Germany)
- Pretreatment: Washed twice with chlorine free tap water. Adjustment to a dry sludge concentration of 3.0 g/L ± 10 % was not necessary. The sludge was used within 24 h after sampling.

Dry weight activated sludge: 3.2 g/L

Study design

Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h

Test conditions

Hardness:
Not determined
Test temperature:
20 °C
pH:
pH-value of the activated sludge 7.08

Salinity:
Not determined
Nominal and measured concentrations:
100 - 320 - 1000 - 3200 - 10000 mg/L (nominal)
Details on test conditions:
TEST SYSTEM
- Test vessel: 500 mL Erlenmeyer flask
- Aeration: Shaking of flasks at 150 rpm to keep the dissolved oxygen concentration above 60 - 70 % saturation and to maintain the sludge flakes in suspension.
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
After 3 h incubation, the oxygen concentration of each control, reference item and test item replicate was determined by means of oximeter immediately after transfering the solution to the measuring cell and the oxygen depletion was recorded for at least 3 minutes on a flatbed recorder.

Reference substance (positive control):
yes
Remarks:
Copper (II) sulphate pentahydrate p.a.

Results and discussion

Effect concentrations
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
1 696 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: 95% CI (1404-2048 mg/L)
Details on results:
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: None
Results with reference substance (positive control):
- Results with reference substance valid? Yes
- Relevant effect levels: EC50: 107 mg/L
Reported statistics and error estimates:
The NOEC was determined by calculation of statistical significance of the inhibition of respiration in comparison to the control. One Way Analysis of Variance (ANOVA) and DUNNETT’s test was used for NOEC calculations. When running a One Way Analysis of Variance a Normality test and an Equal Variance test were done first. P-values for both Normality and Equal Variance test are 0.05. The a-value (acceptable probability of incorrectly concluding that there is a difference) is a=0.05.

The EC-values of the test item and the reference item were calculated by linear regression using software GraphPadPrism. Calculations of the confidence intervals for the EC-values were carried out using standard procedures.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
The EC50 of Sorbitanmonococoat is 1696 mg/L. Sorbitancocoat is not toxic up to the concentration of 417mg/L (EC20) to activated sludge of a municipal sewage treatment plant.