Oestr-5(10)-ene-3,17-dione

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:

Oct 2003

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Sampling method: SampIes for the concentration analysis by TOC were taken at 0, 24, 48 and 72 hours after start of exposure.
The calculated results derived from TOC analysis gave mean concentrations of 11.5 mg/L (saturated solution).

Vehicle:

no

Details on test solutions:

For the preparation of the test solutions, a suspension with a nominal loading of 100 mg/L was ultrasonified (30 min) and stirred for approximately 24h at room temperature. This suspension was filtered through a glassfibre filter. The resulting solution served as the highest concentration (saturated solution). It was further diluted 1:1.25 by adding nutrient solution and inoculum for the highest concentration, and diluted 1:5, 1:10, 1:25, 1:50 and 1:100 with demineralized water, inoculum (2.5 mL) and nutrient solution (2.5 mL) for the other concentrations, all by electronically controlled syringe.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

The alga was obtained from the "Sammlung von Algenkulturen, Universität Göttingen" and kept on slant agar containing a nutrient solution under standardized conditions (10-15 °C, diffuse light (light/dark rhythm 12h/12h)). This culture was dissolved in a nutrient solution and subsequently transferred once weekly.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

The temperature was 22-24 °C during the whole test period, fulfilling the validity criterion.

pH:

The pH was between 7.7 to 9.1. For technical reasons, no pH can be analysed at the beginning of the test. Since the pH cannot be adjusted throughout the test, this criterion has no further significance for the test. Therefore, the measurement of pH after incubation indicates whether extreme pH increases (>10) occurred due to algal growth.

Nominal and measured concentrations:

A nominal concentration of 100 mg/L was used as the stock solution. This corresponds to a measured concentration of 11.5 mg/L. It was further diluted 1:1.25 by adding nutrient solution and inoculum for the highest concentration, and diluted 1:5, 1:10, 1:25, 1:50 and 1:100 with demineralized water, inoculum (2.5 mL) and nutrient solution (2.5 mL) for the other concentrations, all by electronically controlled syringe.

Details on test conditions:

TEST SYSTEM
- Initial cells density: 100000 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 5

GROWTH MEDIUM
- Standard medium used: yes

OTHER TEST CONDITIONS
- Photoperiod: continuous light
- Light intensity and quality: 6000 - 8000 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: fluorescence every 24 h

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.14 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: 95% CI: 0.06 - 0.27 mg/L

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.23 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% CI: 0.19 - 0.42 mg/L

Details on results:

As a parameter for the growth of the algal population, the fluorescence of the algal cells was measured with a fluorescence photometer. The increase in biomass and the growth rate was calculated on the basis of the fluorescence. The calculated biomass and growth rate of each concentration were compared to those of the controls, and the inhibition was calculated.

Results with reference substance (positive control):

No positive control used.

Table 1: Inhibition of biomass and the growth rate (%) of Desmodesmus subspicatus after 72 hours exposure to ZK 67026

		Inhibition in percent ZK 67026 (mg/L)
Dilution of ZK 67026	Concentration of ZK 67026	Biomass (integral)	Growth rate
0	0.0 (control)	0.0	0.0
1:100	0.1	43.0	16.3
1:50	0.2	74.0	50.7
1:25	0.5	87.3	82.0
1:10	1.2	93.6	107.5
1:5	2.3	91.6	97.6
1:1.25	9.2	100.1	112.3

Validity criteria fulfilled:

yes

Conclusions:

The test item had a concentration-depended inhibitory effect on the growth of Desmodesmus subspicatus.
The EbC50 (biomass) was 0.14 mg/L [95% confidence limits: 0.06-0.27 mg/L], the ErC50 (growth rate) was 0.23 mg/L [95% confidence limits: 0.19-0.24 mg/L] on the basis of TOC- measured concentrations.

Executive summary:

The purpose of this study was to detennine the effects of the test compound Delta-5-Norandrostendion (ZK 67026) on the growth of the green algae Desmodesmus subspicatus. The study was conducted according to OECD 201.

The test substance was incubated in an aqueous solution including nutrients with an algae population of Desmodesmus subspicatus for a test duration of approximately 72 hours in an electronically controlled dosing and incubation apparatus. The nutrient solution was made up of mainly ammonia, phosphates and some trace elements. For the preparation of the test solutions a suspension with a nominal concentration of 100 mg/L in water was ultrasonified for approximately 30 min and stirred for approximately 24 hours. This suspension was filtered through a glassfibre filter. The resulting solution was used for the preparation of the test solutions. The highest concentration was obtained from a 1: 1.25 dilution by adding nutrient solution and inoculum, the further concentrations were obtained by dilutions of 1:5, 1:10, 1:25, 1:50, and 1:100 with demineralized water, nutrient solution and inoculum. Additionally, a control solution was prepared with demineralized water without test material. The organic carbon concentration of the stock solution was analyzed with a TOC analyzer in a sample taken at the start of the incubation. The substance concentration was calculated on the basis of the molecular formula. It was 11.5 mg/L. The further test concentrations were extrapolated from the result of the TOC-analysis and are shown in the table below. The algae were exposed to each concentration in triplicate. Six vessels were prepared for the control. The algae were incubated under standardized conditions (continuous light, controlled temperature). As a parameter for the growth of the algae population, the fluorescence of the algal cells was measured with a fluorescence-photometer. The increase of biomass and the growth rate were calculated on the basis of the fluorescence. The calculated biomass and growth rate of each concentration were compared to those of the controls, and the inhibition was calculated.

The biomass and growth rate was inhibited at all dilutions. This was considered to be a compound related effect. The study resulted in an ErC50 (72 h) of 0.23 mg/L (measured).

Description of key information

The EbC50 (biomass) was 0.14 mg/L [95% confidence limits: 0.05-0.19 mg/L], the ErC50 (growth rate) was 0.23 mg/L [95% confidence limits: 0.20-0.27 mg/L] on the basis of TOC-measured concentrations.

Key value for chemical safety assessment

EC50 for freshwater algae:

0.23 mg/L