Cobalt disodium ethylenediaminetetraacetate

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:

experimental study

Adequacy of study:

key study

Study period:

From October 08 to 12, 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Sampling method: 400 mg test item/L was freshly prepared with dilution water. The dispersion was agitated until the solution was visually clear. The stock solution was diluted to obtain the required test item concentrations

Vehicle:

no

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: Pseudokirchneriella subcapitata
- Strain: HINDÁK, CCAP 278/4
- Source (laboratory, culture collection): SAMS Research Services Ltd, Dunstaffnage Marine Laboratory- Dunbeg, OBAN; Argyll PA37 1QA; Scotland, UK
- Method of cultivation at test facility: fresh stocks are prepared every month on Z-Agar. Light intensity amounted to 2590 - 5180 lux corresponding to 35 - 70 µE ∙ m-2 ∙ s-1 for 24 hours per day

ACCLIMATION
- Culturing media and conditions (same as test or not): Nutrient medium Z according to LÜTTGE et al. (1994);

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

21 - 24°C, controlled at ± 2°C

Nominal and measured concentrations:

10.2 - 25.6 - 64.0 - 160 - 400 mg/L (nominal concentration)
0.0171 – 0.0617 – 0.157 – 0.140 – 0.220 mg/L (geometric mean measured cobalt concentrations)

Details on test conditions:

TEST SYSTEM
- Test vessel: Erlenmeyer flasks
- Type (delete if not applicable): open / closed
- Material, size, headspace, fill volume: Sterile glass Erlenmeyer flasks, volume: 250 mL
- Test volume: 100 ml
- Initial cells density: approximately 5 x 103 - 104 cells/mL
- Control end cells density: 6442 cells/mL
- No. of organisms per vessel:
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes. EDTA was not included in the medium in order to avoid interferences with the test item

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Photoperiod: 24 hours/day light
- Light intensity and quality: Approximately 4440 to 8880 lux, corresponding to 60 to 120 µE*m-2*s-1

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Chlorophyll measurement: the cell density was measured daily via Chlorophyll a-fluorescence, excitation at 436 nm, emission at 685 nm. Dilution water was used as a background signal. No self-fluorescence was found in the definitive test at the concentration of 400 mg/L.


TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2.5

Range finding study
- Test concentrations:0.100 - 1.00 - 10.0 – 100 mg/L (nominal). The measured concentrations were below the lowest calibration level (0.002 mg/L) in all test concentrations.

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

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:

EC50

Effect conc.:

> 235 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Details on results:

The EC50-values for inhibition of growth rate (ErC50) and yield (EyC50) after 72 hours were > 400 mg/L [0.220 mg Co2+/L] and 235 (138 - 363) mg/L [0.190 (0.158 - > 0.220) mg Co2+/L], respectively. The NOEC for both growth rate and yield was 160 mg/L [0.140 mg Co2+/L]. The measured concentrations of cobalt at the start of the exposure (0 hours) were between 0 and 1% of the nominal concentrations and at the end of the exposure (72 hours) between of 1 and 8% of the nominal concentration because most of the Co-complex remained undissociated.

Results with reference substance (positive control):

The toxicity of potassium dichromate (SIGMA ALDRICH, batch number MKBV0900V, purity 99.0%, CAS RN 7778-50-9) to the unicellular freshwater green alga Pseudokirchneriella subcapitata was determined over a period of 72 hours from 2018-09-25 to 2018-09-28. The reference item toxicity is in the valid range following test facility SOPS

Validity criteria fulfilled:

yes

Conclusions:

ErC50 > 400 mg/l based on nominal concentration

Executive summary:

Method

The toxicity of the test item to the unicellular freshwater green alga Pseudokirchneriella subcapitata was determined according to the principles of OECD guideline 201.

The aim of the study was the determination of the effects on growth rate and yield over a period of 72 hours. 

The study was conducted under static conditions with an initial cell density of 6442 cells/mL. A stock solution with a nominal loading of 400 mg test item/L was freshly prepared with dilution water. This dispersion was agitated until the solution was visually clear. The stock solution was diluted to obtain the required test item concentrations. Five concentrations were tested in a geometrical series with a spacing factor of 2.5: 10.2 - 25.6 - 64.0 - 160 - 400 mg/L, corresponding to the geometric mean measured cobalt concentration of 0.0171 – 0.0617 – 0.157 – 0.140 – 0.220 mg/L.

Three replicates were tested for each test item concentration and six replicates for the control. The environmental conditionswere within the acceptable limits.

 

The concentrations of the test item were analytically verified via spectrophotometric analysis at the start (0 hours) and at the end of the exposure (72 hours).

The measured concentrations of Cobaltat the start of the exposure (0 hours) were between 0 and 1% of the nominal concentration. At the end of the exposure (72 hours), the Cobalt concentration was detected in the range of 1 and 8 % of the nominal concentration

Results

The EC₅₀-values for inhibition of growth rate (E_rC₅₀) and yield (E_yC₅₀) after 72 hours were > 400 mg/L [0.220 mg Co²⁺/L] and 235 (138 - 363) mg/L [0.190 (0.158 - > 0.220) mg Co²⁺/L], respectively. The NOEC for both growth rate and yield was 160 mg/L [0.140 mg Co²⁺/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:

key study

Study period:

From October 08 to 12, 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

For the detailed read across justification see the document provided in section 13.2 of this dossier.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

assessment report

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Sampling method: 400 mg test item/L was freshly prepared with dilution water. The dispersion was agitated until the solution was visually clear. The stock solution was diluted to obtain the required test item concentrations

Vehicle:

no

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: Pseudokirchneriella subcapitata
- Strain: HINDÁK, CCAP 278/4
- Source (laboratory, culture collection): SAMS Research Services Ltd, Dunstaffnage Marine Laboratory- Dunbeg, OBAN; Argyll PA37 1QA; Scotland, UK
- Method of cultivation at test facility: fresh stocks are prepared every month on Z-Agar. Light intensity amounted to 2590 - 5180 lux corresponding to 35 - 70 µE ∙ m-2 ∙ s-1 for 24 hours per day

ACCLIMATION
- Culturing media and conditions (same as test or not): Nutrient medium Z according to LÜTTGE et al. (1994);

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

21 - 24°C, controlled at ± 2°C

Nominal and measured concentrations:

10.2 - 25.6 - 64.0 - 160 - 400 mg/L (nominal concentration)
0.0171 – 0.0617 – 0.157 – 0.140 – 0.220 mg/L (geometric mean measured cobalt concentrations)

Details on test conditions:

TEST SYSTEM
- Test vessel: Erlenmeyer flasks
- Type (delete if not applicable): open / closed
- Material, size, headspace, fill volume: Sterile glass Erlenmeyer flasks, volume: 250 mL
- Test volume: 100 ml
- Initial cells density: approximately 5 x 103 - 104 cells/mL
- Control end cells density: 6442 cells/mL
- No. of organisms per vessel:
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes. EDTA was not included in the medium in order to avoid interferences with the test item

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Photoperiod: 24 hours/day light
- Light intensity and quality: Approximately 4440 to 8880 lux, corresponding to 60 to 120 µE*m-2*s-1

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Chlorophyll measurement: the cell density was measured daily via Chlorophyll a-fluorescence, excitation at 436 nm, emission at 685 nm. Dilution water was used as a background signal. No self-fluorescence was found in the definitive test at the concentration of 400 mg/L.


TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2.5

Range finding study
- Test concentrations:0.100 - 1.00 - 10.0 – 100 mg/L (nominal). The measured concentrations were below the lowest calibration level (0.002 mg/L) in all test concentrations.

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

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:

EC50

Effect conc.:

> 235 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Details on results:

The EC50-values for inhibition of growth rate (ErC50) and yield (EyC50) after 72 hours were > 400 mg/L [0.220 mg Co2+/L] and 235 (138 - 363) mg/L [0.190 (0.158 - > 0.220) mg Co2+/L], respectively. The NOEC for both growth rate and yield was 160 mg/L [0.140 mg Co2+/L]. The measured concentrations of cobalt at the start of the exposure (0 hours) were between 0 and 1% of the nominal concentrations and at the end of the exposure (72 hours) between of 1 and 8% of the nominal concentration because most of the Co-complex remained undissociated.

Results with reference substance (positive control):

The toxicity of potassium dichromate (SIGMA ALDRICH, batch number MKBV0900V, purity 99.0%, CAS RN 7778-50-9) to the unicellular freshwater green alga Pseudokirchneriella subcapitata was determined over a period of 72 hours from 2018-09-25 to 2018-09-28. The reference item toxicity is in the valid range following test facility SOPS

Validity criteria fulfilled:

yes

Conclusions:

ErC50 > 400 mg/l based on nominal concentration

Executive summary:

Method

The toxicity of the test item to the unicellular freshwater green alga Pseudokirchneriella subcapitata was determined according to the principles of OECD guideline 201.

The aim of the study was the determination of the effects on growth rate and yield over a period of 72 hours. 

The study was conducted under static conditions with an initial cell density of 6442 cells/mL. A stock solution with a nominal loading of 400 mg test item/L was freshly prepared with dilution water. This dispersion was agitated until the solution was visually clear. The stock solution was diluted to obtain the required test item concentrations. Five concentrations were tested in a geometrical series with a spacing factor of 2.5: 10.2 - 25.6 - 64.0 - 160 - 400 mg/L, corresponding to the geometric mean measured cobalt concentration of 0.0171 – 0.0617 – 0.157 – 0.140 – 0.220 mg/L.

Three replicates were tested for each test item concentration and six replicates for the control. The environmental conditionswere within the acceptable limits.

 

The concentrations of the test item were analytically verified via spectrophotometric analysis at the start (0 hours) and at the end of the exposure (72 hours).

The measured concentrations of Cobaltat the start of the exposure (0 hours) were between 0 and 1% of the nominal concentration. At the end of the exposure (72 hours), the Cobalt concentration was detected in the range of 1 and 8 % of the nominal concentration

Results

The EC₅₀-values for inhibition of growth rate (E_rC₅₀) and yield (E_yC₅₀) after 72 hours were > 400 mg/L [0.220 mg Co²⁺/L] and 235 (138 - 363) mg/L [0.190 (0.158 - > 0.220) mg Co²⁺/L], respectively. The NOEC for both growth rate and yield was 160 mg/L [0.140 mg Co²⁺/L].

Description of key information

A study according to OECD 201 was conducted on Co(NH4)EDTA. A read across approach to CoNa2EDTA is reasonable (see the justification provided in section 13.2 of this dossier). Based on the nominal concentrations of the Co-EDTA-complex it can be stated that the EC50 is > 400 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:

400 mg/L