Registration Dossier

Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
2012-05-28 - 2012-07-17
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
GLP guideline study on supporting substance. This result is read-across from ‘1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-nonanethiol’. Read-across is justified as the two substances ‘1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-dodecanethiol’ and ‘1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-nonanethiol’ are virtually the same: the only difference between those two UVCB substances is that one of the used raw materials (alkanethiol) has a diversity in the C-range, i.e. on the one hand a tert. C12-alkanethiol is used in the manufacturing process, on the other hand a tert. C9. Hence, based on the (structural) similarity of both substances it is safe to say that the physicochemical, toxicological and ecotoxicological properties are likely to be similar.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2012
Report date:
2012

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Qualifier:
according to guideline
Guideline:
EU Method C.3 (Algal Inhibition test)
GLP compliance:
yes (incl. QA statement)
Remarks:
The Department of Health of the Government of the United Kingdom

Test material

Constituent 1
Reference substance name:
1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-nonanethiol
EC Number:
293-927-7
EC Name:
1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-nonanethiol
Cas Number:
91648-65-6
Molecular formula:
not applicable (UVCB substance)
IUPAC Name:
1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-nonanethiol
Test material form:
other: liquid
Details on test material:
- Name of test material: 1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-nonanethiol
- Physical state: amber colored liquid
- Storage condition of test material: Room temperature in the dark

Sampling and analysis

Analytical monitoring:
yes
Details on sampling:
- pH mesurement: Initiation of the test and after 72 h exposure
- temperature measurement: Daily

Test solutions

Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Water Accommodated Fractions (WAFs)
- Preparation: 200 mg of test substance were each separately added to the surface of 2 L of culture medium to give the 100 mg/L loading ratey. After the addition of the test substance, the culture medium was magnetically stirred. Such a stirring rate was chosen that a vortex was formed to give a dimple at the water surface. The stirring was stopped after 23 hours and the mixtures were allowed to stand for 1 hour. A wide bore glass tube, covered at one end with Necsofilm was submerged into the vessel, sealed end down, to a depth of approximately 5 cm from the bottom of the vessel. A length of Tygon tubing was inserted into the glass tube and pushed through the Nescofilm seal. Microscopic inspection of the WAFs showed no micro-dispersions or undissolved test substance to be present. The aqueous phase or WAF was removed by mid-depth siphoning (the first approximate 75 - 100 mL discarded) to give the test loading rate WAFs.
The concentration and stability of the test substance in the preparations were verified by chemical analysis at 0 and 72 hours.
- Validation of mixing period: Pre-study work was carried out to determined whether stirring for a prolonged period produced significantly higher measured test concentrations in the WAF. A WAF of a nominal loading rate of 100 mg/L was prepared, in duplicate, in deionized reverse osmosis water. One loading rate was stirred for a period of 23 hours and the other for a period of 71 hours. After a 1-h standing period the mixtures were then removed by siphon and the concentration of the test substance in the 100 mg/L loading rate WAFs was verified by chemical analysis.

Test organisms

Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Strain: CCAP 278/4
- Source: Culture Collection of Algae and Protozoa (CCAP), SAMS Research Services Ltd., Scottish Marine Institute, Oban, Argyll, Scotland.
- Age of inoculum (at test initiation):
- Method of cultivation: Master cultures were maintained in the laboratory by the periodic replenishment of culture medium, constant aeration and illumination at 21 +/- 1 °C
- Master culture conditions: Master culture was added to approx. 100 mL volumes of culture media in conical flasks, which were plugged with polyurethane foam stoppers. The flasks were kept under constant agitation (orbital shaker, 100 - 150 rpm) and constant illumination at 24 +/- 1 °C.
- Initial cell density: approx. 10E3 cells/mL
- Final cell density: 10E4 - 10E5 cells/mL

Study design

Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Post exposure observation period:
No post exposure observation period described.

Test conditions

Hardness:
Not applicable.
Test temperature:
24 +/- 1 °C
pH:
Control (mean from 6 replicates): 7.1 (start) - 7.9 (end)
100 mg/L (mean from 6 replicates): 6.8 (start) - 7.7 (end)
Dissolved oxygen:
No details available.
Salinity:
Not applicable.
Nominal and measured concentrations:
0 and 100 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: conical flasks
- Type: closed
- Material, size, fill volume: glass, 250 mL, 100 mL
- Aeration: none
- No. of vessels per concentration (replicates): 6
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Detailed composition: 25.5 mg/L NaNO3, 12.164 mg/L MgCL2 x 6 H2O, 4.41 mg/L CaCl2 x 2 H2O, 14.7 mg/L MgSO4 x 7 H2O, 1.044 mg/L K2HPO4, 15.0 mg/L NaHCO3, 0.1855 mg/L H3BO3, 0.415 mg/L MnCl2 x 4 H2O, 0.00327 mg/L ZnCl2, 0.159 mg/L FeCl3 x 6 H2O, 0.00143 mg/L CoCl2 x 6 H2O, 0.00726 mg/L Na2MoO4 x 2 H2O, 0.000012 mg/L CuCl2 x 2 H2O, 0.30 mg/L Na2EDTA x 2 H2O
The culture medium was prepared using reverse osmosi purified deionized water (Elga Optima 15+) and the pH adjusted to 7.5 +/- 0.1 with 0.1 N NaOH or HCl.

OTHER TEST CONDITIONS
- Photoperiod: continuous illumination
- Light intensity and quality: approx. 7000 lux provided by warm white lighting (380 - 730 nm)

EFFECT PARAMETERS MEASURED
- Determination of cell concentrations: at 0, 24, 48 and 72 h using a Coulter(R) Multisizer Particle Counter

RANGE FINDING TEST
- Test concentrations: 10 and 100 mg/L
- Results used to determine the conditions for the definitive study: No effect on growth was observed at 10 and 100 mg/L.
Reference substance (positive control):
yes
Remarks:
Potassium dichromate

Results and discussion

Effect concentrationsopen allclose all
Duration:
72 h
Dose descriptor:
EL10
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
other: loading rate WAF
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EL20
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
other: loading rate WAF
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
other: loading rate WAF
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOELR
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
other: loading rate WAF
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EL10
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
other: loading rate WAF
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
EL20
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
other: loading rate WAF
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
other: loading rate WAF
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
NOELR
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
other: loading rate WAF
Basis for effect:
biomass
Details on results:
- Mean cell density of control: 7.62 x 10E3 cells/mL (start) and 6.69 x 10E5 cells/mL (end)
- Observation of abnormalities: none reported
- Solubility: No globules or micro-dispersions were observed by microscopic examination
- Color: At the start of the experiment, all cultures were observed to be clear colorless solutions. After 72 h, the cultures were observed to be pale green dispersions.
Results with reference substance (positive control):
- ErC50(72h): 1.4 mg/L with 95 % CL: 1.2 - 1.7 mg/L
- EbC50(72h): 0.59 mg/L with 95 % CL: 0.53 - 0.65 mg/L
- NOECr(72h): 0.25 mg/L
- NOECb(72h): 0.25 mg/L
- LOECr(72h): 0.50 mg/L
- LOECb(72h): 0.50 mg/L
The results from the positive control were within the normal range for this reference item (Potassium dichromate).
Reported statistics and error estimates:
- Determination of statistically significant differences between test and control groups: Student´s t-test incorporating Bartlett´s test for homogeneity variance (Sokal and Rohlf, 1981)
- Software package: SAS (1999 - 2001)

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Remarks:
Validation criteria of the applied guideline are fulfilled.
Conclusions:
The report describes a valid guideline study conducted under certificated GLP compliance. The obtained 48h-EL50 value (> 100 mg/L WAF) does not lead to a certain toxicity concern of the test substance.
Executive summary:

The acute toxicity of the supporting substance ‘1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-nonanethiol’ (CAS#91648-65-6) towardsPseudokirchneriella subcapitata was investigated according to OECD 201 / EU Method C.3 under certificated GLP compliance. Pseudokrichneriella subcapitata is a freshwater unicellular alga, thus a representative of primary producers found in natural waters and can therefore be considered as an important non-target organism in freshwater ecosystems. Based on the poor water solubility of the test substance (< 0.1 mg/L at 20°C), a modification of the standard method for the preparation of aqueous media was performed. Using the approach of Water Accommodated Fractions (WAFs), based upon an approach by several important regulatory authorities in the EU and elsewhere, aqueous media are prepared by mixing the test substance with water for a prolonged period. Pre-study work showed that a preparation period of 24 hours was sufficient to ensure equilibration between the test substance and the water phase. After a 1-hour settlement period, the test substance is phase is separated by siphon and the test organisms exposed to the aqeous phase or WAF. Based on the results of a range-finding test (no effects at 10 and 100 mg/L WAF), the definitive test was conducted as "limit test" with a single loading rate of 100 mg/L to confirm that no effect on algal growth was observed. Six substance concentration and control replicates were prepared. Samples were taken at 0, 24, 48 and 72 h and the cell densities were determined using a Coulter(R) Multisizer Particle Counter. The pH was measured at the start and end of the test, the temperature was recorded daily. Potassium dichromate was used as reference substance, revealing an ErC50(72h) of 1.4 mg/L with 95 % CL of 1.2 - 1.7 mg/L and an EbC50(72h) of 0.59 mg/L of 0.53 - 0.65 mg/L. The NOEC was 0.25 mg/L and the LOEC was determined as 0.50 mg/L. At the start of the experiment all cultures were observed to be clear colorless solutions. After 72 h, the cultures were recorded as pale green dispersions. In the microscopic examination, neither globules nor micro-dispersions were present. The temperature was maintained at 24 +/- 1 °C throughout the test. The pH in the control cultures increased from pH 7.1 (0 h) to 7.9 (72 h). Differences between test and control groups were determined by Student´s t-test incorporating Bartlett´s test for homogeneity of variance (Sokal and Rohlf, 1981). Concerning growth rate, the ErC10(72h), ErC20(72h) and ErC50(72h) are reported as > 100 mg/L WAF in each case. The NOELr is reported as 100 mg/L WAF. Identical results are reported regarding yield inhibition, whereat all obtained results in this study are also applicable for the closely related substance1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-dodecanethiol’.