Registration Dossier

Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

Currently viewing:

Administrative data

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:
Feb - 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.:
34.1 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks on result:
other: 95% CL = 27.2 - 43.3
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 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 ZK 56407/56510

 Nominal concentration of  

 Inhibition in percent  

 ZK 56407/56510 (mg/L)    Biomass (integral)    Growth rate  
 0,0 (control)   0 0
3,1 5,1 -2,6
6,3 2,1 0,7
12,5 19,1 8,4
25 41,5 19,4
50 66,6 39,3
100 76,7 45,2
Validity criteria fulfilled:
yes
Conclusions:
ZK 56407 and its hydrolysis product ZK 56510 had a concentration-depended inhibitory effect on the growth of Desmodesmus subspicatus.
The EbC5O (biomass) was 34.1 mg/L [95% confidence limits: 27.2 - 43.3], the ErC50 (growth rate) was> 100 mg/L.
Consequently, ZK 56407 and its hydrolysis product were considered to be harmful to the green algae Desmodesmus subspicatus, since the EbCso was between 10 and 100 mg/L.
Executive summary:

The purpose ofthis study was to determine the effects ofthe test compound Valeriansäureanhydrid (ZK 56407) on the growth of the green algae Desmodesmus subspicatus. ZK 56407 is an intermediate ofthe synthesis of various steroids. It is an acid anhydride and hydrolyzes quickly to the corresponding acid (ZK 56510). Therefore, the acid is the predominant compound available in the test. The study was conducted in agreement with the test guideline OECD no. 201.

The test substance ZK 56407 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 phosphates and some trace elements. For the preparation of the test solutions 125 mg/L ZK 56407 was suspended in water, ultrasonified for approximately 30 min and constantly stirred for approximately one hour. The resulting solution was fixed to a pR of 7.0 and used for the preparation ofthe 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 :2.5, 1 :5, 1: 10, 1 :20, and 1 :40 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 sampie taken at the start of the incubation. If the substance concentration is calculated on the basis ofthe molecular formula ofthe hydrolysis product ZK 56510, it was 145.5 mglL, corresponding to 116.4 mg/L in the 1 :1.25 dilution. If it is based on ZK 56407, it was slightly lower (106,2 mg/L). The nominal concentration (100 mg/L) was used for the following calculations in this test. The algae were exposed to each concentration in triplicate. Six vessels were prepared for the control. The algae were incubated under standardized conditions (continous 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 ofbiomass 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 relevantly (> 10%) inhibited from concentrations of 12.5 and 25.0 mg/L upwards, respectivily. This was considered to be a compound related effect.

Description of key information

ZK 56407 and its hydrolysis product ZK 56510 had a concentration-depended inhibitory effect on the growth of Desmodesmus subspicatus.

The EbC5O (biomass) was 34.1 mg/L [95% confidence limits: 27.2 - 43.3], the ErC50 (growth rate) was> 100 mg/L.

Consequently, ZK 56407 and its hydrolysis product were considered to be harmful to the green algae Desmodesmus subspicatus, since the EbCso  was between 10 and 100 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
100 mg/L

Additional information