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Toxicity to aquatic algae and cyanobacteria

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Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2010-04-30 to 2010-07-13
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Version / remarks:
2006
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
yes
Details on sampling:
In order to confirm correct dosage and stability of exposure concentration samples (about 50 mL) of the control and all test concentrations were taken from separate vessels including culture medium (controls), test solutions and algae at 0 h and 72 h. In order to remove the algae from the test solutions, AES-analysis was performed after centrifugation of the samples at 3950 rpm for 10 minutes, followed by dilution of the samples in deionised water to meet the linear range of the calibration lines.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
The test solutions were prepared in a dilution series from a stock solution of 100 mg/L of the test item in culture medium for the range-finding test and from a stock solution of 400 mg/L of the test item in culture medium for the definitive test, respectively. The stock solutions and the corresponding dilutions were prepared using a mixing device (Ultra-Turrax, Janke & Kunkel; 8000 rpm, 2 minutes). The test solutions were clear at all test concentrations. The range-finding test and the definitive test were performed as static tests, i.e., without renewal of the test solutions. The controls were kept in culture medium. Vessels including culture medium (controls) and test solutions were kept under the same conditions as the test vessels for concentration analysis. Concentration analysis was performed at 0 h and 72 h. The Alga-test was carried without adjustment of the pH.

Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name: Desmodesmus subspicatus (Chlorophyceae, Chlorococcales),
- Strain: SAG 86.81
- Source (laboratory, culture collection): Albrecht von Haller Institut für Pflanzenwissenschaften der Universität Göttingen
- Method of cultivation: Sterile on agar tubes (0.8 % Agar). Transferred to a new agar tube every 2 months.

Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
24.2 to 24.7 °C
pH:
in the flasks at 0 h:
7.7 to 8.0

in the flasks at 72 h:
9.6 to 10.5

The test item had a significant effect on the pH of the test solutions at the start of the exposure period.
Nominal and measured concentrations:
Nominal test concentrations: Control, 25.0 mg/L, 50.0 mg/L, 100 mg/L, 200 mg/L, 400 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: 250 mL Erlenmeyer flasks (test volume 100 mL)
- Aeration: none
- Initial cells concentration: 5000 cells/mL
- No. of vessels per test group (replicates): 3
- No. of vessels per control group (replicates): 3

GROWTH MEDIUM
- Standard medium used: yes

Reference substance (positive control):
no
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 400 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
80 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
25 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
50 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
112 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: yield
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
130 mg/L
Nominal / measured:
nominal
Conc. based on:
other: calculated for lithium nitrate
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
652 mg/L
Nominal / measured:
nominal
Conc. based on:
other: calculated for lithium nitrate
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
41 mg/L
Nominal / measured:
nominal
Conc. based on:
other: calculated for lithium nitrate
Basis for effect:
growth rate
Details on results:
The test item had no significant effect on the pH of the test solutions at the start of the exposure period. The increase of pH in the control and test concentrations of 25.0 to 400 mg/L during the exposure period is caused by the growth of the algae in the test vessels. In common with other species of freshwater algae, Desmodesmus subspicatus gains CO2 from HCO3-, leading to a release of hydroxide ions, that raise the pH of the medium. In the test the increase of pH in the control of 2.6 (> 1.5 units as recommended in OECD-Guideline 201) had no effect on the growth of the algae as the validity criteria for algal growth were fulfilled.

Reported statistics and error estimates:
The Kolmogorov-Smirnov-test determined normality of the data (α = 0.05). The results of a one-way ANOVA showed a significant effect on the specific growth rate [µ] in the presence of Lithium chloride (F = 132.8; F critical = 5, 12, α = 0.05 = 3.11). Bartlett`s test detected homogeneity of variances(α = 0.05). Dunnett`s test for comparison of the treatment groups with the control showed significant differences between the control and the effective concentrations of 50.0, 100, 200 and 400 mg/L (α = 0.05).

Concentration of the test item, cells/mL in the test flasks at 72 h, average specific growth rate [µ] over the whole testing period 0-72 h, mean value of the average specific growth rate [µ], standard deviation and coefficient of variation Vc[%], inhibition [%] and mean value of inhibition [%] of the average specific growth rate [µ] in the definitive test:

Concentration

[mg/L]

Cells / mL

Average

Specific

growth rate

[µ]

Average

Specific

growth rate

[µ]

Mean value

Standard deviation

Coefficient of variation

Vc [%]

Inhibition of Average

Specific

growth rate

[%]

Inhibition of Average

Specific

growth rate

Mean value

[%]

 

72 h

0-72 h

0-72 h

0-72 h

0-72 h

0-72 h

0-72 h

Control 1

720000

1.66

 

1.66

 

 

0.01

 

 

0.90

 

 

 

 

 

 

 

Control 2

752000

1.67

Control 3

688000

1.64

25.0

720000

1.66

 

1.66

 

 

0.01

 

 

0.87

 

-0.01

 

-0.52 *

 

25.0

720000

1.66

-0.01

25.0

776000

1.68

-1.52

50.0

576000

1.58

 

1.56

 

 

0.02

 

 

1.26

 

4.48

 

5.65 **

 

50.0

544000

1.56

5.63

50.0

512000

1.54

6.85

100

288000

1.35

 

1.42

 

 

0.07

 

 

4.59

 

18.4

 

14.2 **

 

100

424000

1.48

10.6

100

368000

1.43

13.5

200

248000

1.30

 

1.28

 

 

0.03

 

 

2.64

 

21.4

 

22.6 **

 

200

248000

1.30

21.4

200

208000

1.24

25.0

400

144000

1.12

 

1.11

 

 

0.02

 

 

2.05

 

32.4

 

33.2 **

 

400

128000

1.08

34.8

400

144000

1.12

32.4

* Remark: A negative inhibition value means an enhancement of the parameter.

** Significant difference compared to the control according to Dunnett`s test (p = 0.05).

Validity criteria fulfilled:
yes
Conclusions:
In this 72-h algal growth inhibition test with Desmodesmus subspicatus the 72-h EC50 based on growth rate was determined as greater than 400 mg/L. The overall NOEC was determined to be 25 mg/L. The results are based on the nominal concentrations.
Executive summary:

A test on toxicity to algae with lithium nitrate is not available. Consequently, read-across was applied using study results obtained from a supporting substance, lithium chloride.

The effect of lithium chloride on the growth of the algal species Desmodesmus subspicatus over a 72 hour static exposure period was assessed according to OECD guideline 201. The test solutions were prepared in a dilution series from a stock solution of 100 mg/L of the test item in culture medium for the range-finding test and from a stock solution of 400 mg/L of the test item in culture medium for the definitive test, respectively. The stock solutions and the corresponding dilutions were prepared using a mixing device (Ultra-Turrax, Janke & Kunkel; 8000 rpm, 2 minutes). The test solutions were clear at all test concentrations. The controls were kept in culture medium. Vessels including culture medium (controls) and test solutions were kept under the same conditions as the test vessels for concentration analysis. AES-analysis confirmed that the test solutions were correctly dosed, i.e. the recoveries were within 91.9 to 98.2 % of the nominal concentrations at study start. At the end of the exposure, i.e. after 72 hours, the recoveries ranged from 92.4 to 97.8 % of the nominal concentrations demonstrating that the lithium concentrations were stable throughout the exposure period. Consequently, the results of the definitive test were based on nominal concentrations. In this 72-h algal growth inhibition test with Desmodesmus subspicatus the 72-h EC50 based on growth rate was determined as greater than 400 mg/L. The overall NOEC was determined to be 25 mg/L. The results are based on the nominal concentrations.

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
other: legislative text
Adequacy of study:
supporting study
Study period:
1991, 1998, 2000
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Legal Directives of the European Community regarding nitrate pollution in drinking water.
Key result
Dose descriptor:
other: limit concentration
Effect conc.:
50 mg/L
Conc. based on:
other: Concentration based on nitrate ions.
Dose descriptor:
other: limit concentration
Effect conc.:
55.6 mg/L
Conc. based on:
other: Calculated for LiNO3
Conclusions:
A limit concentration of 50 mg/L nitrate (equivalent to 55.6 mg LiNO3/L) in drinking water was agreed in the Drinking water Directive.
Executive summary:

As laid down in Council Directive 98/83/EC a limit concentration of 50 mg/L nitrate (equivalent to 55.6 mg LiNO3/L) in drinking water was agreed. Also Directive 2000/60/EC and Council Directive 91/676/EEC refer to the limit value laid down in the Drinking Water Directive.

Description of key information

In this 72-h algal growth inhibition test with Desmodesmus subspicatus the 72-h EC50 based on growth rate was determined as greater than 400 mg/L. The overall NOEC was determined to be 25 mg/L. The results are based on the nominal concentrations. Based on read-across approach, the calculated EC10, EC50 and NOEC for lithium nitrate are 130, 652, and 41 mg/L, respectively.

Key value for chemical safety assessment

EC50 for freshwater algae:
652 mg/L
EC10 or NOEC for freshwater algae:
41 mg/L

Additional information

Key study

A test on toxicity to algae with lithium nitrate is not available. Consequently, read-across was applied using study results obtained from a supporting substance, lithium chloride.

The effect of lithium chloride on the growth of an algal species Desmodesmus subspicatus over a 72 hour static exposure period was assessed according to OECD guideline 201. The test solutions were prepared in a dilution series from a stock solution of 100 mg/L of the test item in culture medium for the range-finding test and from a stock solution of 400 mg/L of the test item in culture medium for the definitive test, respectively. The stock solutions and the corresponding dilutions were prepared using a mixing device (Ultra-Turrax, Janke & Kunkel; 8000 rpm, 2 minutes). The test solutions were clear at all test concentrations. The controls were kept in culture medium. Vessels including culture medium (controls) and test solutions were kept under the same conditions as the test vessels for concentration analysis. AES-analysis confirmed that the test solutions were correctly dosed, i.e. the recoveries were within 91.9 to 98.2 % of the nominal concentrations at study start. At the end of the exposure, i.e. after 72 hours, the recoveries ranged from 92.4 to 97.8 % of the nominal concentrations demonstrating that the lithium concentrations were stable throughout the exposure period. Consequently, the results of the definitive test were based on nominal concentrations. In this 72-h algal growth inhibition test with Desmodesmus subspicatus the 72-h EC50 based on growth rate was determined as greater than 400 mg/L. The overall NOEC was determined to be 25 mg/L. The results are based on the nominal concentrations. (Steinbeis, 2010)

Based on read-across approach, the calculated EC10, EC50 and NOEC for lithium nitrate are 130, 652, and 41 mg/L, respectively. (Steinbeis, 2010)

Supporting data

As laid down in Council Directive 98/83/EC a limit concentration of 50 mg/L nitrate (equivalent to 55.6 mg LiNO3/L) in drinking water was agreed. Also Directive 2000/60/EC and Council Directive 91/676/EEC refer to the limit value laid down in the Drinking Water Directive.