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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2017-06-12 to 2017-10-26
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)
Version / remarks:
2011
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Version / remarks:
2009
Deviations:
no
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
- Sampling method: at test start, after 24 and 48 hours and at the end of the test (after the 72 hours test period)
- Sample storage conditions before analysis: 4 ± 4°C
- Fortified samples: 50 mg of the test item were dissolved in 50 mL acetonitrile to obtain a stock solution of approx.1 g test item/L. Different dilutions were carried out and exact values are documented in the raw data of the study.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION:
- Stock solution: 400.4 mg of test item/L in 2002 mL test water, mixed manually;
- Dilutions of stock solution: 1:1, 1:2, 1:4, 1:8, 1:16 prepared for testing
- Controls: test water without addition of the test item
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: Pseudokirchneriella subcapitata
- Strain: No. 61.81 SAG
- Source: available in study report
- Age of inoculum (at test initiation): 3 days old pre-culture
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Hardness:
0.24 mmol/L as CaCO3
Test temperature:
21.8 to 23.9 °C
pH:
6.0 to 6.1 at test start and 6.3 to 6.5 at test end
Nominal and measured concentrations:
Nominal concentrations: stock solution (test substance in test media with a concentration as close to saturation as possible) and dilutions of 1:2, 1:4, 1:8, 1:16
Measured concentrations (geometric mean measured): 0.495, 0.164, 0.0488, 0.0350 and 0.0253 mg test item/L
Details on test conditions:
TEST SYSTEM
- Test vessel: Erlenmeyer flasks of 50mL volume
- Initial cells density: at test start approx. 5000 algal cells/mL were incubated (nominal)
- Control: reconstituted water (OECD medium), test water without addition of the test item
- No. of organisms per vessel: approx. 5000 algal cells/mL
- No. of treatment groups: 6 (5 dose rates of the test item and a control)
- No. of replicates: 3 per test concentration and 6 for the control

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: OECD medium

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Photoperiod: continuous illumination
- Light intensity (mean): 5045 lux

EFFECT PARAMETERS MEASURED: influence of test item on yield and growth rate of organisms

RANGE-FINDING STUDY
- Test concentrations: test item dissolved in OECD medium and stock solution dilutions of 1:10, 1:100, 1:1000
- Sampling points : at test start (0h) and test end (72h).
- Results used to determine the conditions for the definitive study: nominal concentration of 200 mg test item/L caused inhibition rates of 96.1 % for yield and 100 % for growth rate. The lower concentrations showed no inhibitory effect on algal cell growth.
Reference substance (positive control):
yes
Remarks:
Potassium dichromate tested at least twice a year
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
0.113 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
0.064 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
0.049 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
0.076 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: Yield inhibition
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
0.043 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: Yield inhibition
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
0.049 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: Yield inhibition
Details on results:
- Exponential growth in the control (for algal test): yes
- Unusual cell shape: no morphological abnormalities
Results with reference substance (positive control):
- Results with reference substance valid? yes
- EC50: 1.12 mg/L growth rate inhibition (95% conf. interval) and 0.549 mg/L yield inhibition (95% conf. interval)
- EC10: 0.541 mg/L growth rate inhibition (95% conf. interval) and 0.278 mg/L yield inhibition (95% conf. interval: )
Reported statistics and error estimates:
Based on the calculated cell densities, the 72 hours ErC50 and the 72 hours EyC50 (see Definitions), the corresponding EC20 and EC10 values and where possible their 95%-confidence limits were calculated by Probit analysis.
For the determination of the 72 hours LOEC and the 72 hours NOEC, the calculated growth rates and yields at each test concentration were tested for significant differences compared to the control values by Williams t-test.
The software used to perform the statistical analysis was ToxRat Professional, Version 3.2.1, ToxRat Solutions GmbH.

Growth rate during test period of 72 h:

Geometric mean measured concentration (mg test item/L) no. of replicates Growth rates μ [1/day] after (mean)
0-24h 0-48h 0-72h
Control 6 1.434 1.796 1.596
standard dev 0.376 2.728 11.597
0.0253 3 1.577 1.806 1.601
standard dev 0.313 2.829 13.522
0.0350 3 1.457 1.761 1.561
standard dev 0.313 4.123 7.215
0.0488 3 0.926 1.402 1.579
standard dev 0.205 1.379 14.177
0.164 3 0.688 0.460 0.316
standard dev 0.118 0.121 1.048
0.495 3 0.184 0 0
standard dev 0.092 0 0

Growth Rates μ and percentage inhibition of μ during the test period:

Geometric mean measured concentration (mg test item/L) no. of replicates 0-24h 0-48h 0-72h
% inhibition of μ % inhibition of μ % inhibition of μ
Control 6 / / /
0.0253 6 -10 -0.5 -0.3
0.0350 6 -1.6 2 2.2
0.0488 6 35.4 21.9 1.1
0.164 6 52 74.4 80.2
0.495 6 87.2 100 100

Results for the determination of the test item in the test samples:

Sample description
(mg test item/L)
Age (h)
0 (fresh) 24 (aged) 48 (aged) 72 (aged)
Control        
Rep 1 < LOD < LOD < LOD < LOD
Rep 2 < LOD < LOD < LOD < LOD
E.F. 2.5
Concentration calculated-mean  n.a. n.a. n.a. n.a.
1:16 dilution of stock solution        
Rep 1 0.135 < LOQ < LOQ < LOD
Rep 2 0.140 < LOQ < LOQ < LOD
E.F. 2.5
Concentration calculated-mean  0.055 0.025 0.025 0.012
1:8 dilution of stock solution        
Rep 1 0.252 0.131 < LOQ < LOD
Rep 2 0.238 0.125 < LOQ < LOD
E.F. 2.5
Concentration calculated-mean 0.098 0.051 0.025 0.012
1: 4 dilution of stock solution        
Rep 1 0.468 0.253 < LOQ < LOD
Rep 2 0.478 0.247 < LOQ < LOD
E.F. 2.5
Concentration calculated-mean 0.189 0.100 0.025 0.012
1:2 dilution of stock solution        
Rep 1 0.984 0.521 0.317 0.175
Rep 2 0.960 0.523 0.311 0.182
E.F. 2.5 
Concentration calculated-mean 0.389 0.209 0.126 0.071
stock solution        
Rep 1 2.107 1.203 1.261 0.788
Rep 2 2.188 1.185 1.019 0.810
E.F. 2.5
Concentration calculated-mean 0.859 0.478 0.456 0.320
Validity criteria fulfilled:
yes
Conclusions:
After an exposure of 72 h, the test item was found to inhibit the growth of Pseudokirchneriella subcapitata. The reported EC50-values are 0.113 mg/L for growth rate inhibition and 0.076 mg/L when yield inhibition was studied. The 72-hour EC10-values for inhibition of growth rate and yield were 0.064 and 0.043 mg/L, respectively.
Executive summary:

For this endpoint, one study is available in which the effect of the test item on growth of freshwater green algae Pseudokirchneriella subcapitata after 72 hours exposure was assessed according to OECD 201. The organisms were exposed over a period of 72 hours to 5 concentrations of the test item (nominal concentrations were stock solution and its dilutions: 1:2, 1:4, 1:8, 1:16).

Validity criteria were fulfilled with this test set-up.

The test item was found to inhibit the growth of Pseudokirchneriella subcapitata. The 72-hour EC50-values with 95 % confidence intervals for both inhibition of growth rate (ErC50) and yield (EyC50) were 0.113 and 0.076 mg/L. The EC10-values for inhibition of growth rate and yield after 72 hours were 0.064 and 0.043 mg/L, respectively.

Description of key information

ErC50 (72 h): 0.113 mg/L based on growth inhibition of Pseudokirchneriella subcapitata (OECD 201)

ErC10 (72 h): 0.064 mg/L based on growth inhibition of Pseudokirchneriella subcapitata (OECD 201)

Key value for chemical safety assessment

EC50 for freshwater algae:
0.113 mg/L
EC10 or NOEC for freshwater algae:
0.064 mg/L

Additional information

One experimental study is available investigating the toxicity of the substance to aquatic freshwater algae. The study was conducted according to OECD 201 and GLP under static conditions using Pseudokirchneriella subcapitata. 5 dilution levels of 1:1, 1:2, 1:4, 1:8 and 1:16 corresponding to geometric mean measured concentrations of 0.495, 0.164, 0.0488, 0.035 and 0.0253 mg/L. The test concentrations were verified by GC-FID analysis after 0, 24, 48,72 hours. Based on geometric mean measured concentrations, Inhibition of growth was recorded resulting in an ErC50 of 0.113 mg/L and an ErC10 of 0.064 mg/L after 72 h.