Cesium acetate

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Study period:

2011-05-23 to 2011-10-03

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP, OECD study

Justification for type of information:

In water, cesium acetate will dissociate into cesium and acetate ions. Therefore, aquatic organisms living in the column water will never be in direct contact with cesium acetate as such. For short-term toxicity to aquatic algae and cyanobacteria, no study is currently availbale for cesium acetate. However, due to the dissociation in water, toxicity to algae can be extrapolated from studies made from available cesium salts and acetate ion (e.g. acetic anhydride).
In this dossier, the toxicity provokes by the cesium ion has been provide with cesium hydroxide and cesium iodide. In addition, toxicity to acetate has also been provided via acetic anhydride (Acetic anhydride is rapidly hydrolyzed (half-life 4.4 min.) to acetic acid which then, end into acetate and H+).

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Version / remarks:

, adopted 23rd March, 2006

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Version / remarks:

dated July 23, 2009

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Sampling preparation:
For the analysis of the test item concentration, samples from the test media of the test concentration and the control were taken at the start and at the end of the experiment. Representative samples in duplicate series were taken. One series were sent for analysis, and were analyzed immediately after sampling. The analysis was performed depending on the results of the analytical method validation.

- Storage of the Samples: The second series of samples were stored in a refrigerator immediately after sampling, and were kept stored until delivery of the final report to enable additional analyses on request of the sponsor. After delivery of the final report, all samples will be discarded.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Formulation: A solution of the test item with a concentration of 100 mg/L in Algal Mineral Salts Test Medium (“OECD Medium”) was prepared before the start of the experiment.

- Untreated Control: Algal Mineral Salts Test Medium was inoculated (without test item) and examined parallel.

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

TEST ORGANISM
- Source: SAG: Collection of Algal Cultures, Inst. Plant Physiology, University of Göttingen, Nikolausberger Weg 18, D-37073 Göttingen, Germany
- Breeding conditions: The stock cultures are small algal cultures that are planted on agar regularly. These are transferred to fresh medium at least once every two months under standardized conditions according to the test guidelines.
The pre-culture is intended to give an amount of algae suitable for the inoculation of test cultures. The pre-culture was prepared with Algal Mineral Salts Culture Medium, incubated under the conditions of the test and used when still exponentially growing, normally after an incubation period of about three days. The pre-cultured algal cultures were healthy and did not contain deformed or abnormal cells.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

21.8 - 22.2 °C

pH:

pH 8.23 to 8.53 at test start
pH 8.78 to 9.70 at test end

Nominal and measured concentrations:

Nominal: 6.25; 12.5; 25, 50 and 100 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Erlenmeyer flasks of 250 mL volume with 100 mL test medium. The test flasks were covered with air-permeable stoppers.
- Initial cells density: Approximately 10.000 algal cells per mL test medium
- Replicates: 3 replicates per test concentration and six replicates in the control group. Volumes of 100 mL algal suspension per replicate were continuously shaken by a laboratory orbital shaker.


GROWTH MEDIUM
- Standard medium used: yes


OTHER TEST CONDITIONS
- Adjustment of pH: Yes, with HCL to ca. 8.11
- Light intensity and quality: 8000 lux (in average of 8046 lux)

EFFECT PARAMETERS MEASURED:
- Determination of cell concentrations: Manual cell counting using a microscope with a counting chamber
- Other: The cell morphology was examined in parallel

TEST CONCENTRATIONS
- Range finding study: Two non-GLP preliminary range-finding tests were performed. In the first range-finding test the examined nominal concentrations were: 0.1, 1, 5, 10, 50 and 100 mg test item/L. In the second range-finding test the same concentration range was investigated.
- Results used to determine the conditions for the definitive study: The parallel running analytical determination (non-GLP, informative) confirmed the nominal concentrations of 50 and 100 mg test item/L.

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

133.99 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

CsOH monohydrate

Basis for effect:

growth rate

Remarks on result:

other: 95% CL: 99.24 - 180.91 mg/L

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

12.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

CsOH monohydrate

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

25 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

CsOH monohydrate

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

119.62 mg/L

Nominal / measured:

estimated

Conc. based on:

other: calculated for CsOH anhydrous

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

11.2 mg/L

Nominal / measured:

nominal

Conc. based on:

other: calculated for CsOH anhydrous

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

22.3 mg/L

Nominal / measured:

nominal

Conc. based on:

other: calculated for CsOH anhydrous

Basis for effect:

growth rate

Details on results:

At the start and at the end of the test the three highest (nominal) concentrations, 25, 50 and 100 mg/L were above the quantification limit (the limit of quantification of the analytical method was 19 mg cesium hydroxid monohydrat/L) of the analytical method, and these measured test item concentrations were 96-108 % of the nominal at the start and 96-110 % of the nominal at the end of the test. The concentrations of 6.25 and 12.5 mg/L were out of the measurable range. There is evidence that the concentrations of the tested substance (25-100 mg/L) were satisfactorily maintained within ± 20 % of the nominal concentrations throughout the test. The two lowest not analysed concentration levels were considered as being within the ± 20 % of the nominal range; therefore the analysis of the results was based on the nominal concentration values. All reported biological results are related to the nominal concentrations of the test item.

Results with reference substance (positive control):

The ErC 50 of Potassium dichromate: 1.52 mg/L, (95 % confidence limits: 1.40 – 1.64 mg/L). The growth rate, 72h value is in accordance with the accepted 1.10 ± 0.48 mg/L range for Pseudokirchneriella subcapitata.

Reported statistics and error estimates:

The EC50 values of the test item and their confidence limits were calculated using Probit analysis. The analysis was done using the TOXSTAT statistical software program.
For the determination of the LOEC and NOEC, the calculated mean biomass b (area under the growth curve), growth rates r and yield at the test concentrations were tested on significant differences to the control values by Bonferroni t-Test (TOXSTAT software). The data were checked for normality by Chi-Square Test, for homogeneity of variance by Levene’s Test.

The test item had a statistically significant inhibitory effect on the growth based on the average specific growth rate, yield and areas under the growth curves of Pseudokirchneriella subcapitata after the exposure period of 72 hours in the concentration range of 25–100 mg test item/L (Bonferroni t-Test, α=0.05).

Cell Density in Control: In the control the cell density has increased from nominal N= 1 x 104 cells/mL at the start of the test (0 hours) to N= 72.83 x 104 cells/mL (mean value) after 72 hours by a factor of 72.83. Thus, the algal growth in the control was high enough to pass the validity criteria in this assay.

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of this acute algal growth inhibition test on Pseudokirchneriella subcapitata the observed endpoints for the effect of cesium hydroxide monohydrate based on the growth rate were the following: 72h EC50 value: 133.99 mg test item/L; 72h NOEC value: 12.5 mg test item/L and 72h LOEC value: 25 mg test item/L.
Based on these data the 72h-EC50 calculated for cesium hydroxide anhydrous was 119.62 mg/L., the 72h-LOEC was 22.3 mg/L and the 72h NOEC was 11.2 mg/L. All reported biological results are related to the nominal concentrations.
Regarding the extrapolation for cesium acetate, the values have been calculated as: 72h-EC50: 153.17 mg/L., 72h-LOEC 28.55 mg/L and the 72h NOEC 14.34 mg/L

Executive summary:

An Acute Growth Inhibition Test of cesium hydroxide monohydrate on Algae (Pseudokirchneriella subcapitata) over an exposure period of 72 hours in a static system was assessed according to OECD Guideline 201 and EU method C.3. Five different concentrations arranged in a geometric series and an untreated control group were tested in the main study. The highest concentration was 100 mg/L. The following concentrations were used in the main study: 6.25; 12.5; 25, 50 and 100 mg/L. The shape of the algal cells growing was obviously not affected. Under the conditions of this acute algal growth inhibition test on Pseudokirchneriella subcapitata the observed endpoints for the effect of cesium hydroxide monohydrate based on the growth rate were the followings: 72h EC50 value: 133.99 mg test item/L (estimated); 72 EC50 >100 mg test item/L; 72h NOEC value: 12.5 mg test item/L and 72h LOEC value: 25 mg test item/L.

Based on these data the 72h-EC50 calculated for cesium hydroxide anhydrous was 119.62 mg/L., the 72h-LOEC was 22.3 mg/L and the 72h NOEC was 11.2 mg/L.

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Study period:

2011-06-21 to 2011-06-24

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: accordding to GLP and according to OECD and EU guidelines

Justification for type of information:

In water, cesium acetate will dissociate into cesium and acetate ions. Therefore, aquatic organisms living in the column water will never be in direct contact with cesium acetate as such. For short-term toxicity to aquatic algae and cyanobacteria, no study is currently availbale for cesium acetate. However, due to the dissociation in water, toxicity to algae can be extrapolated from studies made from available cesium salts and acetate ion (e.g. acetic anhydride).
In this dossier, the toxicity provokes by the cesium ion has been provide with cesium hydroxide and cesium iodide. In addition, toxicity to acetate has also been provided via acetic anhydride (Acetic anhydride is rapidly hydrolyzed (half-life 4.4 min.) to acetic acid which then, end into acetate and H+).

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Version / remarks:

, 2006

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Version / remarks:

, July 23, 2009

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Sampling, Analysis, Analytical Method: At the start and end of the experiment two parallel samples were taken from each concentration level and from the control. Representative samples (in duplicate series) were taken at the start and at the end of the experiment. One series was stored frozen in the testing laboratory, one series was sent for analysis, and was analysed immediately after sampling. The analysis was performed according to the results of the validated flame photometer analytical method.

Vehicle:

yes

Details on test solutions:

Formulation: A solution of the test item with a concentration of 100 mg/L in Algal Mineral Salts Test Medium (“OECD Medium”) was prepared before the start of the experiment.

Untreated Control: Algal Mineral Salts Test Medium was inoculated (without
test item) and examined parallel.

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

TEST ORGANISM
- Common name: Pseudokirchneriella subcapitata (formerly known as Selenastrum capricornutum) (Printz-Starr)
- Source (laboratory, culture collection): The algae were supplied by the SAG: Collection of Algal Nikolausberger Weg 18, D-37073 Göttingen, GERMANY
- Breeding Conditions: The stock cultures are small algal cultures that are planted on agar regularly. These are transferred to fresh medium at least
once every two months under standardized conditions according to the test guidelines. The pre-culture is intended to give an amount of algae
suitable for the inoculation of test cultures. The pre-culture was prepared with Algal Mineral Salts Culture Medium, incubated under the conditions of the test and used when still exponentially growing, normally after an incubation period of about three days. The pre-cultured algal cultures were healthy and did not contain deformed or abnormal cells.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

22.6 - 23.4 °C

pH:

pH 7.61 to 7.94 at test start
pH 8.20 to 8.88 at test end;
Validity criteria (The pH did not vary by more than 1.5 units in any one test.) fulfilled

Nominal and measured concentrations:

The nominal test item concentrations were 3.125; 6.25; 12.5; 25; 50; and 100 mg test item/L.
At the start and at the end of the test the two highest (nominal) concentrations, 50 and 100 mg/L were above the quantification limit (the limit of quantification of the analytical method was 29 mg cesium iodide of the analytical method, and these measured test item concentrations were 100-105 % of the nominal at the start and 95-99 % of the nominal at the end of the test. The concentrations of 3.125; 6.25; 12.5 and 25 mg/L were out of the measurable range. There is evidence that the concentrations of the tested substance (3.125-100 mg/L) were satisfactorily maintained within ± 20 % of the nominal concentrations throughout the test. The not analysed concentration levels were considered as being within the ± 20 % of the nominal range; therefore the analysis of the results was based on the nominal concentration values. All reported biological results are related to the nominal concentrations of the test item.

Details on test conditions:

TEST SYSTEM
- Test vessel: Erlenmeyer flasks of 250 mL volume with 100 mL test medium
- Initial cells density: The test was started (0 hours) by inoculation of a biomass of approximately 10.000 algal cells per mL test medium. These cells were taken from an exponentially growing pre-culture, set up three days prior to the test start using the same conditions as in the test.
- Replicates The test was performed with three replicates per test concentration and six replicates in the control group. Volumes of 100 mL algal suspension per replicate were continuously shaken by a laboratory orbital shaker in 250 mL Erlenmeyer flasks. The test flasks were covered with airpermeable stoppers.

GROWTH MEDIUM
- Standard medium used: yes

OTHER TEST CONDITIONS
- Adjustment of pH: No (Validity criteria (The pH did not vary by more than 1.5 units in any one test.) fulfilled)
- Light intensity and quality: approximately 8000 lux (in average of 8573 lux), which was ensured with fluorescent lamps (with a spectral range of 400-700 nm).

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: Manual cell counting using a microscope with a counting chamber
- Other: The cell morphology was examined in parallel

TEST CONCENTRATIONS
- Range finding study: Two non-GLP preliminary rangefinding tests were performed. In both of the range-finding tests the examined nominal concentrations were: 0.1, 1, 5, 10, 50 and 100 mg test item/L.
- Test concentrations: The following concentrations were used in the main study: 3.125; 6.25; 12.5; 25, 50 and 100 mg/L (geometric series).

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 635.75 (95% CL: 211.10 - 1914.59 mg/L)

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

6.25 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

12.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

All reported biological results are related to the nominal concentrations of the test item.

Results with reference substance (positive control):

The ErC 50 of Potassium dichromate: 0.82 mg/L, (95 % confidence limits: 0.77 – 0.61 mg/L)
The EyC 50 of Potassium dichromate: 0.61 mg/L, (95 % confidence limits: 0.58 – 0.65 mg/L)
The growth rate, 72h value is in accordance with the accepted 1.10 ± 0.48 mg/L range for
Pseudokirchneriella subcapitata.

Reported statistics and error estimates:

Mean values and standard deviations were calculated for each treatment at the start, and at the end of the test using Excel for Windows software.
Percentage inhibition of area (A), yield (Y) and growth rate (r) were calculated using EXCEL for Windows software. The EC50 values of the test item and their confidence limits were calculated using Probit analysis. The analysis was done using the TOXSTAT statistical software program. For the determination of the LOEC and NOEC, the calculated mean biomass b (area under the growth curve), growth rates r and yield at the test concentrations were tested on significant differences to the control values by Bonferroni t-Test (TOXSTAT software). The data were checked for normality by Chi-Square Test, for homogeneity of variance by Levene’s Test.

Validity criteria fulfilled:

yes

Conclusions:

In the 72-h algal growth inhibition test on Pseudokirchneriella subcapitata with cesium iodide the observed endpoints based on the growth rate were the following: 72-h EC50 > 100 mg/L (635.75 mg/L); NOEC = 6.25 mg/L; LOEC = 12.5 mg/L.
Regarding the extrapolation for cesium acetate, the values have been calculated as: 72-h EC50 > 100 mg/L; NOEC = 4,61 mg/L; LOEC = 9,23 mg/L.

Executive summary:

The purpose of this study was to determine the effect of the test item cesium iodide on the growth of a unicellular green algal species Pseudokirchneriella subcapitata (formerly: Selenastrum capricornutum). Exponentially growing cultures of Pseudokirchneriella subcapitata were exposed to various concentrations of the test item over several generations under defined conditions. The algal growth in relation to a control culture was determined over a fixed test period of 72 hours and thus, over several algal generations. The test method of application and the test species Pseudokirchneriella subcapitata are recommended by the test guidelines In the 72-h algal growth inhibition test on Pseudokirchneriella subcapitata with cesium iodide, the 72-h EC50 based on biomass was determined to be 47.94 mg/L, based on the growth rate higher than 100 mg/L (635.75 mg/L) and based on the yield the 72-h EC50 was 59.40 mg/L. The nominal test item concentrations were 3.125; 6.25; 12.5; 25; 50; and 100 mg test item/L. The test item concentration of the test solutions was measured by flame photometer method at the start and at the end of the test. At the start and at the end of the test the two highest (nominal) concentrations, 50 and 100 mg/L were above the quantification limit (the limit of quantification of the analytical method was 29 mg test item/L) of the analytical method, and these measured test item concentrations were 100-105 % of the nominal at the start and 95 -99 % of the nominal at the end of the test. The concentrations of 3.125;6.25; 12.5 and 25 mg/L were out of the measurable range.There is evidence that the concentrations of the tested substance (3.125-100 mg/L) were satisfactorily maintained within ± 20 % of the nominal concentrations throughout the test. The not analysed concentration levels were considered as being within the ± 20 % of the nominal range; therefore the analysis of the results was based on the nominal concentration values. All reported biological results are related to the nominal concentrations of the test item. The NOEC was determined to be 6.25 mg/L based on the growth rate and yield, while it was 3.125 mg/L based on biomass. The LOEC was calculated to be 12.5 mg/L based on the growth rate and yield, while it was 6.25 mg/L based on biomass (all calculations were based on nominal concentrations). Therefore, the overall NOEC was determined to be 3.125 mg/L, while the overall LOEC was calculated to be 6.25 mg test item/L.

Reference 3

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

GLP compliance:

not specified

Test organisms (species):

other: Two studies conducted: Chlorella pyrenoidosa (Gloyna, 1967) and Scenedesmus quadricauda (Bringmann, 1980)

Duration:

8 d

Dose descriptor:

other: Toxicity threshold

Effect conc.:

3 400 mg/L

Conc. based on:

test mat.

Remarks on result:

other: made with Scenedesmus quadricauda

Remarks:

Bringmann, 1980

Duration:

5 d

Dose descriptor:

other: reduction compared to controls

Effect conc.:

> 50 - < 400 mg/L

Conc. based on:

test mat.

Remarks on result:

other: made on Chlorella pyrenoidosa

Remarks:

Gloyna, 1967

Duration:

8 d

Effect conc.:

18 mg/L

Conc. based on:

test mat.

Remarks on result:

other: made on Microcystis aeruginosa

Remarks:

Bringmann, 1975

Conclusions:

In the cell multiplication inhibition test (8 days), the following toxic threshold concentrations (EC3) were determined:
- Microcystis aeruginosa (cyanobacteria): 18 mg/l (Bringmann, 1975)
- Scenedesmus quadricauda (green algae): 3,400 mg/l (Bringmann, 1980)
In a 5-day study with Chlorella pyrenoidosa (algae) using chlorophyll reduction as the endpoint, 16.6% to 96.6% reduction was noted compared to the controls over the concentration range 50 mg/l to 400 mg/l (Gloyna, 1967).

Description of key information

No short-term toxicity to aquatic algae and cyanobacteria is currently existing for cesium acetate. However, to fulfil the requirement, read-across strategy with cesium salts have been used to assess the toxicity of cesium acetate (cesium ion) and one supporting study with acetic anhydride to provide data induced by acetate (acetic anhydride is rapidly hydrolyzed (half-life 4.4 min.) to acetic acid which then, ends into acetate and H+).

* CsOH.H2O

Under the conditions (OECD guideline 201) of the acute algal growth inhibition test onPseudokirchneriella subcapitatathe observed endpoints for the effect of cesium hydroxide monohydrate based on the growth rate were the following: 72h EC50 value: 133.99 mg test item/L; 72h NOEC value: 12.5 mg test item/L and 72h LOEC value: 25 mg test item/L.

Based on these data the 72h-EC50 calculated for cesium acetate was calculated as: 72h-EC50: 153.17 mg/L., 72h-LOEC 28.55 mg/L and the 72h NOEC 14.34 mg/L.

* CsI

In the 72-h algal growth inhibition test onPseudokirchneriella subcapitata(OECD guideline 201) with cesium iodide the observed endpoints based on the growth rate were the following: 72-h EC50 > 100 mg/L (635.75 mg/L); NOEC = 6.25 mg/L; LOEC = 12.5 mg/L.

Regarding the extrapolation for cesium acetate, the values were calculated as: 72-h EC50 > 100 mg/L; NOEC = 4,61 mg/L; LOEC = 9,23 mg/L.

* Acetic anhydride

In the cell multiplication inhibition test (8 days), the following toxic threshold concentrations (EC3) were determined:

- Microcystis aeruginosa (cyanobacteria): 18 mg/l (Bringmann, 1975)

- Scenedesmus quadricauda (green algae): 3,400 mg/l (Bringmann, 1980)

In a 5-day study with Chlorella pyrenoidosa (algae) using chlorophyll reduction as the endpoint, 16.6% to 96.6% reduction was noted compared to the controls over the concentration range 50 mg/l to 400 mg/l (Gloyna, 1967).

These values should only be seen as supporting data as the full study report is not available. In addition, the data does not mention if the medium has been neutralized.

Key value for chemical safety assessment

EC50 for freshwater algae:

153.17 mg/L