Dimolybdenum trizinc nonaoxide

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.1 (Acute Toxicity for Fish)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Water samples were taken from the control and all surviving test groups at 0, 24, 48 and 72 hours from fresh media and at 24, 48, 72 and 96 hours from old media for quantitative analysis. Samples were taken for immediate analysis and acidified before analysis. Samples were analyzed for zinc content.

Details on test solutions:

A nominal amount of test item in duplicate (2200 mg) was dispersed in 22 liters of test water with the aid of propeller stirring at approximately 1500 rpm for 48 hours. After 48 hours the stirring of both preparations was stopped, any undissolved test item was removed by filtration through a 0.2 μm Sartorius Sartopore filter (first approximate 1 liter used to pre-condition the filter was discarded) to give a 100% v/v saturated solution.

The 100% v/v saturated solutions from both preparations were pooled in a 44 L capacity tank and then mixed thoroughly with a flat bladed stirrer. A series of dilutions was made from this saturated solution to give test solutions of 1.0, 3.2, 10 and 32% v/v saturated solution.

Each test solution was mixed with a flat bladed stirrer for approximately 1 minute to ensure adequate mixing and homogeneity.

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM
- Common name: Rainbow trout
- Strain: NA
- Source: Fish were obtained from Brow Well Fisheries Limited, Hebden, near Skipton, Yorkshire, UK.
- Age at study initiation (mean and range, SD): Juvenilles
- Length at test termination (length definition, mean, range and SD): 5.4 cm (SD = 0.51)
- Weight at test termination (mean and range, SD): 1.16 g (SD = 0.4)

ACCLIMATION
- Acclimation period: 7 days
- Acclimation conditions (same as test or not): Under test conditions
- Type and amount of food during acclimation: The stock fish were fed commercial trout pellets which was discontinued approximately 27.5 hours prior to the start of the definitive test.
- Feeding frequency during acclimation: Not specified
- Health during acclimation (any mortality observed): There was no mortality in the 7 days prior to the start of the definitive test.

FEEDING DURING TEST
- None

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Remarks on exposure duration:

Standard as per OECD Guideline

Post exposure observation period:

Not applicable

Hardness:

Approximately 140 mg/L as CaCO3

Test temperature:

Temperatures were mainatined at 13 to 14°C throughout the test.

pH:

7.5 to 8.3

Dissolved oxygen:

10 to 11.1 mgO2/L

Salinity:

Not applicable

Conductivity:

Typically 497 µS/cm at 20°C

Nominal and measured concentrations:

Nominal: 1, 3.2, 10, 32 and 100 mgL
Geometric mean measured test concentration as Zinc: 0.027, 0.078, 0.24, 0.81 and 2.5 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Glass exposure vessels
- Type (delete if not applicable): open (covered to reduce evaporation)
- Material, size, headspace, fill volume: 28 L containing 20 liters of test media
- Aeration: Aerated via narrow bore glass tubes
- No. of organisms per vessel: 7
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The test water used for both the range-finding and definitive tests was the same as that used to maintain the stock fish.
Laboratory tap water was dechlorinated by passage through an activated carbon filter (Purite Series 500) and partly softened (Elga Nimbus 1248D Duplex Water Softener) giving water with a total hardness of approximately 140 mg/L as CaCO3. After dechlorination and softening the water was passed through a series of computer controlled plate heat exchangers to achieve the required temperature.

OTHER TEST CONDITIONS
- Adjustment of pH: None
- Photoperiod: 16 hours light to 8 hours darkness cycle
- Light intensity: Not specified

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Any mortalities and sub-lethal effects of exposure were recorded as a minimum at 1, 3, 6, 24, 48, 72 and 96 hours after the start of exposure. The criteria of death were taken to be the absence of both respiratory movement and response to physical stimulation.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: Standard as per guidelines
- Justification for using less concentrations than requested by guideline: NA
- Range finding study
- Test concentrations: 0.01, 0.1, 1 and 10 mg/L.
- Results used to determine the conditions for the definitive study: Based on the results of the range-finding test the following test concentrations were assigned to the definitive test: 1.0, 3.2, 10, 32 and 100 mg/L as a saturated solution.

Reference substance (positive control):

not required

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

68 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

1.7 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

element

Remarks:

Zinc

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

4.6 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat. (dissolved fraction)

Remarks:

Test item calculated based on zinc component

Basis for effect:

mortality (fish)

Details on results:

- Behavioural abnormalities:
- Observations on body length and weight: Not specified
- Other biological observations: Sub-lethal effects of exposure were observed at test concentrations of 10% v/v and above. These responses were swimming at bottom of the vessel and swimming at surface of the test media.
- Mortality of control: None
- Other adverse effects control: None noted
- Abnormal responses: None noted
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: Most of the control and test item preparations were observed to be clear colorless solutions throughout the test, except for the 100% v/v saturated solution preparations at 48 hours (old) and 96 hours (old), which were observed to be very slightly hazy dispersions.

Results with reference substance (positive control):

Not applicable

Reported statistics and error estimates:

Analysis of the mortality data by Probit analysis using Linear Maximum-Likelihood regression based on the nominal, geometric mean measured zinc and mean calculated test item concentrations was employed.

Sublethal observations / clinical signs:

LC50 Responses:

Time	LC50 [95% Confidence limits]
Hour	Nominal Concentrations (% v/v)	Zinc Measured Concentrations (mg/L)	Test item Calculated Concentrations based on zinc (mg/L)
1	> 100	> 2.5	> 6.7
3	> 100	> 2.5	> 6.7
6	> 100	> 2.5	> 6.7
24	> 100	> 2.5	> 6.7
46	> 100	> 2.5	> 6.7
72	84 [43 – 3830]	2.1 [1.1 – 191]	5.7 [2.9 – 534]
96	68 [35 – 215]	1.7 [0.9 – 5.6]	4.6 [2.3 – 15]

Geometric mean calculations:

Nominal Test Concentration (% v/v)	Geometric Mean Measured Test Concentration as Zinc (mg/L)	Test item calculated Concentration based on zinc (mg/L)
1	0.027	0.072
3.2	0.078	0.21
10	0.24	0.65
32	0.81	2.2
100	2.5	6.7

Validity criteria fulfilled:

yes

Remarks:

The test was considered to be valid given that none of the control fish died or showed signs of stress during the test and that the oxygen concentration at the end of the test was ≥60% of ASV (≥6.1 mg O2/L) in the control and test vessels.

Conclusions:

An OECD guideline GLP compliant study with fish provided a 96 hour LC50 value of 1.7 mg/L based on measured zinc concentrations and 4.6 mg/L based on the test substance calculated from the measured zinc concentrations.

Description of key information

An OECD guideline GLP compliant study with fish provided a 96 hour LC50 value of 1.7 mg/L based on measured zinc concentrations and 4.6 mg/L based on the test substance calculated from the measured zinc concentrations.

The effect concentration based on the measured zinc concentrations is considered to be the most conservative for chemical safety assessment purposes.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

1.7 mg/L