19-Norpregn-5(10)-ene-21-nitrile, 17-hydroxy-3-oxo-, (17.alpha.)-

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:

Jan - Mar 2003

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.:

<= 1 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

<= 1 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Table 1: Inhibition of biomass and the growth rate (%) of Desmodesmus subspicatus after 72 hours exposure to ZK37877

		Inhibition in percent
Dilution of ZK37877	Concentration of ZK 37877 (mg/L)	Biornass (integral)	Growth rate
0	0,0 (control)	0	0
1:100	0,24	80,7	64
1:50	0,49	82,4	71,1
1:25	0,97	84,6	77,3
1:10	2,44	88,9	92,9
1:5	4,87	86,1	83,6
1: 1,25	19,5	93,8	101,4

Validity criteria fulfilled:

yes

Conclusions:

5-Dehydrocyanomethylketon had a concentration-depended inhibitory effect on the growth of Desmodesmus subspicatus. The EbC50 (biomass) and the ErC50 (growth rate) was below 1 mg/L. The highest concentration without effect could not be determined, since it was below the lowest
concentration tested. Consequently, ZK 37877 was considered to be very toxic to the green algae Desmodesmus subspicatus, since the EC50
was < 1 mg/L.

Executive summary:

The purpose of this study was to determine the effects of the test compound 5 -Dehydrocyanomethylketon (ZK 37877) on the growth of the green algae Desmodesmus subspicatus. ZK 37877 is an intermediate of the synthesis of Dienogest. The study was conducted in agreement with the test guideline OECD no. 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 nitrate, phosphates and some trace elements. For the preparation of the test solutions a suspension with a nominal loading of 125 mg/L ZK 37877 was suspended in water, ultrasonified for approximately 30 min and constantly 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 I: 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 fonnula. It was 24.4 mg/L. The further test concentrations were extrapolated from the result ofthe TOC-analysis.

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 test concentrations. This was considered to be a compound related effect.

Description of key information

5-Dehydrocyanomethylketon had a concentration-depended inhibitory effect on the growth of Desmodesmus subspicatus. The EbC50 (biomass) and the ErC50 (growth rate) was below 1 mg/L. The highest concentration without effect could not be determined, since it was below the lowest

concentration tested. Consequently, ZK 37877 was considered to be very toxic to the green algae Desmodesmus subspicatus, since the EC50

was < 1 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:

1 mg/L