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Short-term toxicity to aquatic invertebrates

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Reference
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1998
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to guideline
Guideline:
EU Method C.2 (Acute Toxicity for Daphnia)
Deviations:
not specified
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
Sampled for analysis at 0 and 48 hours.
Vehicle:
no
Details on test solutions:
Preparation: Since TPS 32 is poorly soluble in water; a saturated solution was prepared by vigorously mixing: 100 mg of TPS 32 with dilution water during 23 hours at 20°C (preliminary test) and 2 mg of TPS 32 with dilution water during 68 hours at 20°C (definitive test). After this saturation period, the saturated solution was filtered with a HV 0.45 µm filter. Vehicle, solvent: Ultrapure water. Dilution water was prepared in the laboratory using pure water and salts according to ISO 6341.
Test organisms (species):
Daphnia magna
Details on test organisms:
Strain: Daphnia magna straus strain 5 or A. Source/supplier: Breeding colony was realized in Elendt M7 medium in the laboratory, organisms were selected by sieving. Breeding method: Not available. Age: Less than 24 hours. Feeding: Microscopic algae Raphidocelis subcapitata. Pretreatment: No. Feeding during test: No. Control group: Yes.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
48 h
Post exposure observation period:
No
Hardness:
200 ± 20 mg/L as CaCO3
Test temperature:
20 ± 1°C
pH:
8.2 ± 0.2
Dissolved oxygen:
9.2 ± 0.3 mg/L
Salinity:
Not applicable
Nominal and measured concentrations:
Series of approximately dilutions of the dissolved item from 6.25% to 100 % . Concentrations: 6.25, 12.5, 25, 50, 100 nominal concentration (% vol), forming a geometric progression with a factor of 2. Measured concentrations were not available, because the analytical method did not allow the determination of the test substance concentration.
Details on test conditions:
Type and source of exposure medium: ultrafiltered water with carbon exchange. Test vessel: 250 mL glass flasks. No of organisms per vessel: 5. No of replicates per concentration: 4. Photoperiod: Incubation of test flasks in darkness.
Reference substance (positive control):
yes
Remarks:
Potassium dichromate
Duration:
24 h
Dose descriptor:
NOEC
Effect conc.:
< 0.1 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
dissolved
Basis for effect:
mortality
Remarks on result:
other: Limit of quantification
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
< 0.1 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
dissolved
Basis for effect:
mortality
Remarks on result:
other: Limit of quantification
Details on results:
An EC50 was not reported. This may be due to the fact that the test item was not detected at the limit of detection and quantification of the analytical technique due to its very low solubility. A 5% effect was observed at 24hr and 48 hours but this is considered to be not significant as an immobilisation up to 10% is permitted by the TG in the blank control. The limit of detection and quantification for the analytical technique employed was 0.03 and 0.01 mg/l, respectively.
Results with reference substance (positive control):
The sensitivity of the test organism is confirmed by a toxicity test with Potassium dichromate periodically, EC50/24h =1.1mg/l.
Reported statistics and error estimates:
No data reported

Nominal   Measured                Immobile (%)      
conc      Init        Final          
    %      mg/l        24 hr       24 hr    48 hr 
100       <LQ        <LQ             5           5  
50        <LD        <LD             0           5  
25         NA        NA              0           0 
12.5       NA        NA              5           5 
6.25       NA        NA              0           0

Validity criteria fulfilled:
no
Remarks:
The analytical method used in the test did not allow the determination of the substance concentration as the solubility of the substance in the test medium was below the limit of quantification. The stability of the test substance was also not checked.
Conclusions:
An acute EC50 value could not be calculated for polysulfides, di-tert-dodecyl due to its very low solubility in water and hence the low exposure to the this substance. At the solubility limit of the test substance, no significant immobilization if the test organisms was recorded after 24 and 48 hours. Thus the polysulfides, di-tert-dodecyl was not toxic for daphnia at the maximal exposure concentration corresponding to the solubility limit of the polysulfides, di-tert-dodecyl in the test medium. The solubility/dispersibility limit of polysulfides, di-tert-dodecyl in the test medium was below the range of quantification ( i.e., 0.1 mg/l) and above the detection limit (i.e.0.02 mg/l) of the analytical method, therefore 0.02 mg/l < Solubility limit <0.1 mg/l.
Executive summary:

Thiebaud (1998) is a 48 hour, static, freshwater, GLP-compliant test on Daphnia magna, follows EU Method C2. The results no significant toxicity to aquatic invertebrates at the limit of solubility (which is below the limits of analytical detection). The study is considered reliable and suitable for use for this endpoint.

Description of key information

An acute EC50 value could not be calculated for polysulfides, di-tert-dodecyl due to its very low solubility in water and hence the low exposure to the substance. At the solubility limit, no significant immobilization was recorded at 48 hours. Thus the substance was not toxic to daphnia at the maximal exposure concentration (the solubility limit). The solubility/dispersibility limit was below the range of quantification (0.1 mg/l) and above the detection limit (0.02 mg/l) of the analytical method, therefore 0.02 mg/l < solubility limit <0.1 mg/l.

Key value for chemical safety assessment

Additional information

Thiebaud (1998) is a 48 hour, static, freshwater, GLP-compliant test on Daphnia magna, follows EU Method C2. The results indicate that this substance is not significantly toxic to aquatic invertebrates at the limit of solubility (which is below the limits of analytical detection). The study is considered reliable and suitable for use for this endpoint.