Dipotassium tetraoxomolybdate

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Test followed international guidelines for the used test species, physicochemistry was measured and reported, proper statistics were applied

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2008

Report date:

2008

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

GLP compliance:

no

Remarks:

The study was carried out in compliance with the principles of good laboratory practice.

Test material

Test material information

Constituent 1

Reference substance name:

Sodium molybdate dihydrate

IUPAC Name:

Sodium molybdate dihydrate

Constituent 2

Reference substance name:

Reference substance 001

EC Number:

600-158-6

Cas Number:

10102-40-6

Molecular formula:

H2 O. 1/2 Mo O4. Na

Constituent 3

Reference substance name:

not availabble for the tested dihydrate

IUPAC Name:

not availabble for the tested dihydrate

Details on test material:

- Name of test material (as cited in study report): Sodium Molybdate Dihydrate
- Molecular formula (if other than submission substance): Na2MoO4⋅2H2O
- Molecular weight (if other than submission substance): 241.95 g/mol
- Physical state: solid (white crystalline powder)
- Analytical purity: 99.9% (dihydrate form) based on an analysed Molybdenum content of 39.6%
- Expiration date of the lot/batch: 31 December 2008
- Storage condition of test material: at room temperature (10-30°C) in the dark, dry
- no further significant details stated

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

Samples for total Mo (test initiation) and dissolved Mo (test initiation and termination, filtered through 0.45 µm) were taken from all treatments

Test organisms

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: Pseudokirchneriella subcapitata
- Tested life stage: exponential growing algal cells

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test conditions

Hardness:

25 mg/ as CaCO3 (theoretical hardness, based on reported Ca- and Mg content of OECD medium)

Test temperature:

24 degrees Celsius

pH:

pH of Test 1 at start of exposure:: 7.79 - 8.28
pH of Test 1 after 72 hours: 7.54-8.24
pH of test 2 at start of exposure: 7.15-7.59
pH of Test 2 after 72 hours: 7.54-8.35

pH of Test 3 at start of exposure:: 7.09 - 7.61
pH of Test 3 after 72 hours: 7.48-7.94
pH of test 4 at start of exposure: 7.71-8.26
pH of Test 4 after 72 hours: 7.58-8.03

Nominal and measured concentrations:

nominal: control, 46, 100, 220, 460, 1000, 2200, 4600 mg Mo/L
measured - dissolved (at start of Test 1): measured - dissolved (at start of Test 2): measured - dissolved (at start of Test 3): measured - dissolved (at start of Test 4):
measured - dissolved (at end of Test 1): measured - dissolved (at end of Test 2): measured - dissolved (at end of Test 3): measured - dissolved (at end of Test 4):

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Type (delete if not applicable):closed
- Material, size, headspace, fill volume: glass 100mL Erlenmeyers
- Type of flow-through (e.g. peristaltic or proportional diluter): static
- Initial cells density: 10,000 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3



GROWTH MEDIUM
- Standard medium used: yes:
Test 1 & Test 4: OECD-medium prepared by UGent
Test 2 & Test 3: OECD-medium prepared by CIMM


OTHER TEST CONDITIONS
- Photoperiod: 24l/0D (according to OECD guidance)
- Light intensity: 85-125 μE m-2s-1

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: ; electronic particle counter (coulter counter)
- end parameter: growth rate

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

234 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element

Remarks:

Mo-dissolved

Basis for effect:

growth rate

Remarks on result:

other: Test 1

Effect concentrations 2

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

366.2 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element

Remarks:

Mo-dissolved

Basis for effect:

growth rate

Remarks on result:

other: 294.4-455.5 (Test 1)

Effect concentrations 3

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

1 568.9 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element

Remarks:

Mo-dissolved

Basis for effect:

growth rate

Remarks on result:

other: 1431.2-1719.8 (Test 1)

Effect concentrations 4

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

236 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element

Remarks:

Mo-dissolved

Basis for effect:

growth rate

Remarks on result:

other: Test 2

Effect concentrations 5

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

318.6 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element

Remarks:

Mo-dissolved

Basis for effect:

growth rate

Remarks on result:

other: 278.9-363.9 (Test 2)

Effect concentrations 6

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

1 094.5 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element

Remarks:

Mo-dissolved

Basis for effect:

growth rate

Remarks on result:

other: 1019.6-1174.8 (Test 2)

Effect concentrations 7

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

49.6 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element

Remarks:

Mo-dissolved

Basis for effect:

growth rate

Remarks on result:

other: Test 3

Effect concentrations 8

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

61.2 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element

Remarks:

Mo-dissolved

Basis for effect:

growth rate

Remarks on result:

other: 36.5-102.7 (Test 3)

Effect concentrations 9

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

390.9 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element

Remarks:

Mo-dissolved

Basis for effect:

growth rate

Remarks on result:

other: 312.4-489.2 (Test 3)

Effect concentrations 10

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

48.6 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element

Remarks:

Mo-dissolved

Basis for effect:

growth rate

Remarks on result:

other: Test 4

Effect concentrations 11

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

72.6 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element

Remarks:

Mo-dissolved

Basis for effect:

growth rate

Remarks on result:

other: 48.3-109.2 (Test 4)

Effect concentrations 12

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

295 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element

Remarks:

Mo-dissolved

Basis for effect:

growth rate

Remarks on result:

other: 247.8-351.3 (Test 4)

Details on results:

All validity criteria were fulfilled over the 72 hour exposure period.

Reported statistics and error estimates:

Growth rates based on daily cell density of the treatments during 72 hours were calculated according to OECD Guideline No. 201 (OECD, 2006). The effect concentrations (72h-ErC10 and 72h-ErC50) were estimated based on dissolved concentrations at the start of the test using a standard log-logistic concentration-response model. Calculations were performed using Statistica® software.
For the determination of the NOEC the methods recommended by OECD (2005) were used. The Jonckheere-Terpstra trend test (Lehmann, 1975) was used. All hypothesis testing was conducted one-sided at the α level of 0.05 as recommended by OECD (2005). Hypothesis testing was performed with SPSS16® software.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

Following an internationally recognised standard test procedure for the evaluation of chronic toxicity of sodium molybdate for the freshwater green alga Pseudokirchneriella subcapitata, reliable (K1) EC10, EC50 and NOEC-values were derived. Effect levels for standard exposure period and end parameter were based on measured concentration levels.