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Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study without restrictions
Justification for type of information:
The target substance 1,3-propanesultone hydrolyses rapidly. The product of hydrolysis is the source substance 3-hydroxypropanesulphonic acid.
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
PHYSICO-CHEMICAL PROPERTIES
- Stability in water: due to the strucuture, no hydrolysis is expected
Analytical monitoring:
yes
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The test solutions were prepared separately for each test concentration. For this the test substance was pipetted in and was made up with OECD medium to reach concentrations of 111% of the nominal concentration to compensate for the dilution by the later addition of inoculum. To reach the correct nominal concentrations at test start, inoculum culture was added to each 111% stock test solution at a ratio of 1:10.
- Evidence of undissolved material (e.g. precipitate, surface film, etc): All stock test solutions appeared colorless and clear.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
-Test species and strain: Desmodesmus subspicatus CHODAT (SAG 86.81)
- Age (on study day 0): A stock algal culture is maintained continuously at the test facility. Before the exposure an inoculum culture is prepared from the stock culture and incubated for 3 days at 21 – 24 °C (max. temperature difference 2 °C). After this time, the inoculum culture is in exponential growth phase and can be used to initiate the test (study day 0).
- Supplier: Collection of algal cultures in University of Göttingen/Germany
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
21.5 – 22.5 °C
pH:
at 0 h: 7.1 - 7.4
at 72 h: 7.1 - 7.4 (control), 9.5 - 9.6 (test concentrations)
Nominal and measured concentrations:
Nominal test substance concentrations: control, 15.5, 48.3, 155, 483, 1546 mg/L
Nominal concentrations based on the dimer content (20.7%) of the test substance: control, 3.2, 10, 32, 100, 320 mg/L

Geometric mean measured concentrations: 12.6, 41.2, 132, 428, 1321 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel:
- Material, size, headspace, fill volume: Erlenmeyer flasks (nominal volume 250 mL) closed with glass plugs, 100 ml fill volume
- Initial cells density: 0.5 x 10E+04 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6


GROWTH MEDIUM
- Standard medium used: yes, the test medium (OECD medium) was prepared according to OECD Guideline for Testing of Chemicals, No. 201 Algal growth inhibition test, Mar 2006, Annex 3. To accommodate testing in a closed system (see Mayer 2000; ISO/DIS 14442, 2004) the concentration of NaHCO3 in the final modified OECD medium was increased to 300 mg/L and was adjusted to pH 7 by the addition of 1M HCL. The test medium was sterilized after preparation.

OTHER TEST CONDITIONS
- Adjustment of pH: yes for nominal test substance concentrations 100 mg/L (483 mg/L) and 320 mg/L (1546 mg/L)
- Photoperiod: 16:8
- Light intensity and quality: Average 4900 lux (within ±15% variability) at a wave length of 400 - 700 nm

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations:Algal growth measured as in vivo chlorophyll-a fluorescence (pulsed excitation with light flashes having a wavelength of 430 nm) after 0, 24, 48 and 72 hours

TEST CONCENTRATIONS
- Range finding study: yes
- Results used to determine the conditions for the definitive study: ErC50 > 100 mg/L.
Reference substance (positive control):
yes
Remarks:
Potassium dichromate
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
> 320 mg/L
Nominal / measured:
nominal
Conc. based on:
other: Dimer
Basis for effect:
growth rate
Remarks on result:
other: Nominal concentrations (based on the dimer content (20.7%) of the test substance) verified analytically as all measured concentrations of the test substance in the test water deviated less than 20% from the nominal concentration.
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 320 mg/L
Nominal / measured:
nominal
Conc. based on:
other: Dimer
Basis for effect:
growth rate
Remarks on result:
other: Nominal concentrations (based on the dimer content (20.7%) of the test substance) verified analytically as all measured concentrations of the test substance in the test water deviated less than 20% from the nominal concentration.
Details on results:
The pH of the control medium increased by >1.5 units over the course of the test. The OECD 23 guidance document acknowledges that pH will typically increase in a closed system and recommends a reduced initial cell density and additional NaHCO3 in the test medium as were used in this test. The increase in pH did not affect control algal growth since all validity criteria were fulfilled.
Results with reference substance (positive control):
ErC50 (72 h) of potassium dichromate: 1.08 mg/L
Validity criteria fulfilled:
yes
Conclusions:
The product of hydrolysis of 1,3-propanesltone is with high probability not harmful to algae.

Description of key information

The determined EC50(72 h) value >320 mg/L (nominal)

Key value for chemical safety assessment

EC50 for freshwater algae:
320 mg/L
EC10 or NOEC for freshwater algae:
320 mg/L

Additional information

Studies investigating the acute toxicity of 1,3-propanesultone to aquatic algae are not available. The substance hydrolyses rapidly forming 3-hydroxypropanesulphonic acid. The assessment is therefore based on the product of hydrolysis 3-hydroxypropanesulphonic acid. The acute toxicity to the green algae Desmodesmus subspicatus was tested in a guideline study following OECD 201. Detrimental effects were not observed. Based on the algal growth rate an EC50 (72 h) >320 mg/L (nominal concentrations (based on the dimer content (20.7%) of the test substance)) was observed. The determined EC10 was >320 mg/L (nominal concentrations (based on the dimer content (20.7%) of the test substance)).