13-β-ethyl-3-methoxygona-2,5(10)-dien-17-one

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:

Sept 1997

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

Principles of method if other than guideline:

not relevant

GLP compliance:

yes

Analytical monitoring:

yes

Vehicle:

no

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.005 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.077 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 0.047 - 0.107

Table 1: Inhibition of the growth rate (%) of Scenedesmus subspicatus after 72 hours exposure to ZK 28520

Dilution of	Concentration	Inhibition in percent
ZK 28520	of ZK 28520 (mg/I)	Biomass	Growth rate
		(integral)
0	0,0 (control)	0	0
1:1000	0,004	8	0
1 :100	0,04	71	28
1:10	0,4	93	92
Saturated solution	4	98	111

Validity criteria fulfilled:

yes

Conclusions:

D-ET-Dienon had an inhibitory effect on the growth of Scenedesmus subspicatus. The EbC50 (biomass) was 0.005 mg/L (confidence limits could not be calculated), the ErC50 (growth rate) was 0.077 mg/L [95% confidence limits: 0.047-0.107] on the basis of concentrations
extrapolated from TOC analysis. Consequently, D-ET-Dienon is very toxic to the green algae Scenedesmus subspicatus.

Executive summary:

The purpose of this study was to determine the effects of the test compound D-ET-Dienon (ZK 28520) on the growth of the green algae Scenedesmus subspicatus. D-ET-Dienon is an intermediate of the synthesis of levenorgestrel. The study was conducted in agreement with the OECD guideline no. 201.

The test substance was incubated in an aqueous solution including nutrients with an algae population of Scenedesmus subspicatus for a test duration of approximately 72 hours. The nutrient solution was made up of mainly nitrate, phosphates and some trace elements. For the preparation of the test solutions a suspension with a nominal loading of 100 mg ZK 28520/L was stirred for 24 hours. This suspension was filtered through a glassfibre filter. The resulting solution served as the highest concentration (saturated solution). It was further diluted 1:10, 1:100 and 1:1000 with demineralized water. The organic carbon concentration of the stock solution was analysed with a TOC analyser at the start of the incubation. The substance concentration was calculated on the basis of the molecular formula. It was 4.1 mg/L. The test concentrations extrapolated 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 in an incubator shaker under continuous light.

As a parameter for the growth of the algae population, the cell concentrations of the test and control solutions were counted with an electronic particle counter ("Coulter Counter"). The increase of biomass and the growth rate were calculated on the basis of the cell counts. The calculated biomass and growth rate of each concentration were, compared to those of the controls, and the inhibition was calculated.

At 4 mg/L the growth rate was negative and the inhibition was> 100%, accordingly.

Description of key information

D-ET-Dienon had an inhibitory effect on the growth of Scenedesmus subspicatus. The EbC50 (biomass) was 0.005 mg/L (confidence limits could not be calculated), the ErC50 (growth rate) was 0.077 mg/L [95% confidence limits: 0.047-0.107] on the basis of concentrations

extrapolated from TOC analysis. Consequently, D-ET-Dienon is very toxic to the green algae Scenedesmus subspicatus.

Key value for chemical safety assessment

EC50 for freshwater algae:

0.077 mg/L