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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:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Version / remarks:
respiration test according to OECD 1976
Deviations:
no
Principles of method if other than guideline:
The respiration inhibition of the test substance to a sludge concentration of 1.5 g/L suspended solids is recorded after 3 hours.
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
no
Test organisms (species):
activated sludge
Details on inoculum:
- Initial biomass concentration: 1.5 g/L suspended solids
- Source: Rungsted municipal treatment plant, Denmark, treating almost exclusively domestic sewage
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Reference substance (positive control):
not specified
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
135 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Duration:
30 min
Dose descriptor:
EC50
Effect conc.:
188 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Endpoint:
toxicity to microorganisms
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
10 - 11 Feb 1998
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to
Guideline:
DIN 38412-8 (Pseudomonas Zellvermehrungshemmtest)
Deviations:
no
GLP compliance:
yes
Remarks:
Freie und Hansestadt Hamburg, Behörde für Arbeit, Gesundheit und Soziales
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION:
The test substance was diluted with the culture medium just before use. The stock solution concentration was 2000 mg/L.
No analytical monitoring of the test concentrations was performed.
Test organisms (species):
Pseudomonas putida
Details on inoculum:
- Laboratory culture: Stock cultures were obtained from Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH, Braunschweig
- Method of cultivation: The culture was kept on the nutrient used for stock cultures in agar slant tubes. New stock cultures were started every week. The inoculated stock cultures were incubated at 25 ºC.
- Preparation of inoculum for exposure: One day old stock cultures were used as inoculum for preliminary cultures. Bacterial suspension in preliminary culture was diluted under sterile conditions to a concentration corresponding with a turbidity value of TU/F=10.
100 ml of such suspension was incubated using 250 mL Erlenmeyer flasks at 20-21 ºC for about 7 hours. Subsequently, the cultures were mixed and adjusted with further preliminary culture medium to an extinction value of 0.168 (TU/F = 50 ± 1).
- Initial biomass concentration: Turbidity value = 5. The concentration is expressed as the extinction of the primary light of the monochromatic absorbance at 436 nm for a layer thickness of 10 mm.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
16 h
Post exposure observation period:
none
pH:
6.97 - 7.01
Details on test conditions:
TEST SYSTEM
- Test vessel: 250 mL Erlenmeyer flasks
- Fill volume: 10 mL

- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6
- Biomass loading rate: Turbidity value = 5

TEST MEDIUM / WATER PARAMETERS
- Culture medium different from test medium: yes

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: the test was performed in the dark

EFFECT PARAMETERS MEASURED:
- inhibition of cell multiplication

TEST CONCENTRATIONS
100, 178, 316, 562, 1000 mg/L

- Range finding study
- Test concentrations: 31.6 and 100 mg/L
- Results used to determine the conditions for the definitive study: no toxicity was observed
Reference substance (positive control):
no
Duration:
16 h
Dose descriptor:
EC0
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: inhibition of cell multiplication
Duration:
16 h
Dose descriptor:
EC10
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: inhibition of cell multiplication
Duration:
16 h
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: inhibition of cell multiplication
Duration:
16 h
Dose descriptor:
EC100
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: inhibition of cell multiplication
Details on results:
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: no
- Effect concentrations exceeding solubility of substance in test medium: none
Endpoint:
activated sludge respiration inhibition testing
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Remarks:
Summary of available data used for the endpoint assessment of the target substance
Adequacy of study:
key study
Justification for type of information:
Refer to the Category Approach Justification document provided in IUCLID6 Section 13.
Reason / purpose:
read-across source
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
135 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: Source, key, 151-21-3, 1983

Description of key information

3h EC50 (activated sludge, domestic) = 135 mg/L (respiration inhibition test, similar to OECD 209)

Key value for chemical safety assessment

EC50 for microorganisms:
135 mg/L

Additional information

Since no reliable toxicity test with microorganisms is available for Sulfuric acids, C9-11-iso-C10 rich, alkyl esters, sodium salt, in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 a read-across to other structurally related substances was conducted. As the toxicity of alkyl sulfates is dependent on the carbon chain length, it is expected that the C12 and C12-iso homologues will be the worst case scenario for the C9, C10 and C11 homologues.

The non-GLP test (Dutka, 1983) was performed with C12AS Na (CAS 151-21-3) according to a guideline similar to OECD 209. Activated sludge from a municipal sewage treatment plant was used as inoculum. The EC50 values of 188 and 135 mg/L (nominal concentrations) were obtained for the endpoint respiration inhibition after 30 minutes and 3 hours of exposure, respectively. Since the preference is given to tests with a mixed inoculum that assess the functioning of the entire microbial community in an STP, rather than tests based on single species or even microbial sub-systems, this test is considered to be the key study.

Moreover, one reliable GLP study on toxic effects of C12-isoAS Na (CAS 94200-74-5) to microorganisms is available (Sasol, 1998). The test was performed according DIN 38412, part 8 guideline. The EC10 value based on inhibition of cell multiplication determined after 16-hour exposure to the test substance was above 1000 mg/L (nominal concentration).

Due to structural and property similarities with the tested substance, it can be concluded that the above results apply also to Sulfuric acids, C9-11-iso-C10 rich, alkyl esters, sodium salt. The 3-hour EC50 value of 135 mg/L was used for PNEC STP derivation.