SDBR

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

11-14 July 2000 (range-finding study); 15-18 August 2000 (main study)

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Version / remarks:

1992

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Version / remarks:

1984

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Storage conditions: at room temperature, not protected from light

Analytical monitoring:

yes

Details on sampling:

At the start and end of the growth inhibition test, single 100 mL samples were taken from the test series containing nominal test substance concentrations of 0, 0.03, 0.18 and 1.0 mg/L. The samples were placed in brown glass flasks and immediately transferred for analysis.

Vehicle:

yes

Remarks:

Tert.-butanol was used as an auxiliary solvent for dispersal.

Details on test solutions:

For the range-finding test, an amount of 110.4 mg test substance was dissolved in 10 mL TBA using ultrasonic treatment. Dilutions were prepared in TBA so as to yield a test substance concentration series of 0, 0.04, 0.06, 0.11, 0.20, 0.35, 0.62 and 1.1 x 10E4 mg/L.
For the main study, an amount of 101.6 mg SDBR was dissolved in 10 mL TBA using ultrasonic treatment. Dilutions were then prepared in TBA so as to yield a test substance concentration series of 0, 0.03, 0.06, 0.10, 0.18, 0.33, 0.57 and 1.0 x 10E4 mg/L.

The series included concentrations above the water solubility to compensate for the loss of substance during the test due to its reaction with water during the study.

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Remarks on exposure duration:

The algal growth was determined by electronic particle counting after 0, 22.5, 46 and 71 hours incubation.

Hardness:

24.2 mg CaCO3/L

Test temperature:

20.4-25.2ºC

pH:

8.1-8.2 in absence of algal cells;
In the presence of algal cells the final pH was found to have increased to 8.8-9.0.

Nominal and measured concentrations:

The results of analysis are included below in tabular format.

At the start of the test the measured test substance concentrations were found to be 79%-89% of the nominal concentrations (mean value 84%)
The measured test substance concentration decreased during the test, and the final measured concentration was 0.043 mg/L or 36% of the reported solubility in water.

Details on test conditions:

Range-finding test:
Testing was performed in conical test flasks of 200 mL.
A suspension of algae in the algal medium containing 10E4 cells/mL was prepared by dilution of a pre-culture containing 4.86x10E6 cells/mL. A volume of 10 µl of the appropriate solutions of the test substance was added to 100 mL of the algal suspension in the test flasks, yielding a nominal inoculum cell density of 1x10E4 cells/mL and a test concentration series of 0, 0.04, 0.06, 0.11, 0.20, 0.35, 0.62 and 1.10 mg/L.
The test was carried out in duplicate with four controls containing algae only, and a single background series containing test substance without algae. All flasks were incubated at approximately 100 rpm. with light intensity in a range of 60-120 µmol*sE-1*mE-2. After three days of incubation algal densities and biovolume were determined with the electronic particle counter. Measured values were corrected for the background values in the appropriate blanks.

The main study was performed following a similar protocol. The test was carried out in duplicate with four controls containing algae only, and a single background series containing test substance without algae. Algal densities and biovolume were determined after 0, 22.5, 46 and 71 hours.
The pH was measured at the start (medium without algae) and after 72 hours in selected cultures. The morphology of the algae was examined visually with the aid of a microscope at the start and end of the test.

Reference substance (positive control):

yes

Remarks:

The test system used was checked with reference substances K2Cr2O7 and/or 3,5-dichlorophenol on an approximately yearly basis.

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

1.2 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.12 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Details on results:

Range-finding test:
No inhibitory effect was found at nominal test substance concentrations up to and including 1.1 mg/L.
Main study:
Detailed results are given below in tabular format. As no inhibition was observed, the NOEC of SDBR was concluded to be 1.0 mg/L when based on nominal concentrations.
In addition, microscopic inspection of the morphology of algal cells in the preculture at the start of the test revealed normal cells. At the end of the test no abnormal cells were observed in the cultures containing different concentrations of SDBR.

The exposure concentrations during the initial phase of the test were above or at aqueous solubility of SDBR (0.12 mg/L), and did then decrease to a value lower than the water solubility during the test. The NOEC that is based on measured concentrations of SDBR is consequently very close to the reported aqueous solubility limit of 0.12 mg/L.

Results with reference substance (positive control):

The results of the yearly reference tests demonstrate a constant quality of the test system during an extended period of at least 15 years.

Individual growth parameters calculated from the results of the growth inhibition test with SDBR

Nominal conc. SDBR (mg/L)	Calculated inoculum (10E4 particles/mL)	Calculated growth rate (per hour)	Inhibition of growth rate (%)
0	0.6	0.076	-
0.03	0.6	0.077	-0.6
0.06	0.67	0.074	3.6
0.10	0.70	0.072	5.1
0.18	0.63	0.074	3.2
0.33	0.72	0.071	6.4
0.57	0.74	0.070	7.9
1.0	0.62	0.075	1.9

 

Validity criteria fulfilled:

yes

Conclusions:

The NOEC of SDBR was found to be approximately at the aqueous solubility limit of 0.12 mg/L.

Description of key information

The NOEC of SDBR was found to be approximately at the aqueous solubility limit of 0.12 mg/L.