Tricobalt bis(orthophosphate)

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

March-July 2022

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Version / remarks:

2004

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Subsamples were collected from the control, the lowest and the highest test dilutions prior to test commencement and at test termination for chemical analysis. All samples were stored at 4°C in the dark prior to being transported to The Shepherd Color Company for analysis.
Subsamples of the test solutions were sent to The Shepherd Color Company for chemical analysis of the definitive test solutions for confirmation of exposure
concentrations.

Vehicle:

no

Details on test solutions:

The test sample was considered poorly water soluble. Accordingly, preparation of the test solutions followed OECD's Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures (OECD, 2000). A nominal concentration of 100 mg/L was selected as the maximum concentration of the test item to be tested for all range-finding and definitive tests (OECD, 2006). Furthermore, all nominal test solutions were prepared based on the whole product, without correction for purity.

Range Finding Test Solution Preparation:
To prepare the test solution a 1L solution of the highest concentration (i.e., 100 mg/l) was prepared by adding 100mg of Violet 92 into 1L of moderately hard water freshwater in a glass beaker and stirred at 700 rpm for 1 hour at room temperature. This solution will be allowed to settle for approximately 72 hours. Preparation of the remaining test solutions was completed at this time. A total of 900 ml of the 100 mg/l test solution was decanted for testing leaving the settled solids behind. All lower concentrations of the test item (10, 1, 0.1, 0.01) were prepared by serial dilution.

Definitive Test Solution Preparation:
To prepare the test solution a 1.5L solution of the highest concentration (i.e., 100 mg/l) was prepared by adding 150mg of Violet 92 into 1.5L of moderately hard water freshwater in a glass beaker and stirred at 700 rpm for 1 hour at room temperature. This solution will be allowed to settle for approximately 72 hours. Preparation of the remaining test solutions was completed at this time. A total of 1,400 ml of the 100 mg/l test solution was decanted for testing leaving the settled solids behind. All lower concentrations of the test item (100, 50, 25, 12.5, 6.25) were prepared by serial dilution.

The dilution water was moderately hard freshwater with the following composition:
- 64.8 mg/L Magnesium sulfate (anhydrous)
- 110 mg/L Sodium bicarbonate
- 4.36 mg/L Potassium chloride
- 64.8 mg/L Calcium sulfate (dihydrate).

Test organisms (species):

Daphnia magna

Details on test organisms:

The cladoceran D. magna is cultured in mass in aquaculture water at 25°C under 16:8 photoperiod at Hydrosphere Research lab. Lighting is ambient laboratory cool white fluorescent at ~50-100 footcandles. Feeding is daily with YCT and P. subcapitata. Renewal schedule is Monday-Wednesday-Friday. The strain is EPA F2 (Newton, OH 1985).

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

Moderately hard freshwater

Test temperature:

20.0 - 20.8°C - recorded daily

pH:

8.0 - 8.2

Dissolved oxygen:

8.2 - 9.1 mg/L

Conductivity:

320 - 343 umho/cm

Nominal and measured concentrations:

nominal concentrations: 0, 6.25, 12.5, 25, 50, 100 mg/L

Details on test conditions:

- Test type: Static
- Test duration: 48 hours
- Temperature: 20 ± 1 °C, as recorded daily with a max/minimum thermometer (constant within± 1 °C)
- Light quality: Ambient laboratory illumination
- Light intensity: 400 to 800 lux
- Photoperiod: 16-hour light, 8-hour dark
- Feeding regime: None during test
- Test chamber: Glass beaker (30 ml)
- Test volume: 20 ml
- Source of test organisms: In-house culture
- Age of test organisms: <24 hours old
- Number of concentrations for range- finding test: Five concentrations (0.01, 0.1, 1, 10 and 100 mg/L plus a control)
- Number of concentrations for range- finding test: Five concentrations (6.25, 12.5, 25, 50,and 100 mg/L plus a control)
Test replicates: Four per dilution
Number of animals per test chamber: 5
Total Number of organisms per treatment level: 20
Aeration: None
Dilution water Moderately Hard Freshwater
Measured water chemistry parameters: Dissolved oxygen, pH, conductivity at start and end of test, temperature, and visual observations at 0, 24 and 48 hours, dilution water hardness at 0 hours.
- Measured endpoints: 24-, 48-hour EL50
- Test validity criteria: Immobility ≤ 10% in the control

Reference substance (positive control):

yes

Remarks:

Potassium chloride

Key result

Duration:

48 h

Dose descriptor:

EL50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Details on results:

The bioassay tests were acceptable tests based on controls and test conditions specified in the methods. The test met all the test validity criteria.
The results indicate that the 48-hour Effective Loading Rate at the 50% level for D. magna was >100 mg/L.

Results with reference substance (positive control):

The last toxic response obtained on the reference item Potassium chloride (July 1, 2022) gives an LC50-48h of 0.70 g/L, indicating that the daphnids sensitivity is correct.

Reported statistics and error estimates:

For all concentrations and the controls, survival at 24 and 48 hours were calculated for each replicate and then averaged. Due to the low water solubility of the test item, test results will be reported in term of the Effective Loading Rate (EL50), referring to the loading rate that causes an adverse effect (in this case, immobility in 50% of the exposed population) within a specified period (i.e., 24, 48 hours).

Daphnids immobilisation:

Nominal test item concentration in mg/L	% Immobilised daphnids at 0h	% Immobilised daphnids at 24h	% Immobilised daphnids at 48h
Control	0	0	0
6.25	0	5	5
12.5	0	0	0
25	0	5	5
50	0	0	5
100	0	5	45
EL50	> 100 mg/L	> 100 mg/L	> 100 mg/L

Validity criteria fulfilled:

yes

Conclusions:

The results obtained for the test item on the toxicological endpoint 'immobilisation' give an EL50 (48h) > 100 mg/L based on nominal test item concentrations.

Description of key information

The results obtained for the test item in the experimental conditions of an OECD 202 test give an EL50 (48h) > 100 mg/L

based on nominal test item concentrations.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

LC50

Effect concentration:

> 100 ng/L