Molybdenum zinc tetraoxide

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:

11 October 2018 - 19 December 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

The concentration of the test item were measured at each test concentration at the beginning and end of the test in triple determination.
The samples were preserved with acid (HNO3, 65 %) and cool storage.

Vehicle:

no

Details on test solutions:

A stock solution of the test item of 32 mg/l was prepared in dilution water. The solution was stirred overnight at room temperature afterwards. The next day the stock solution was filtered, so that only the dissolved proportion was tested. The test solutions were prepared by adding dilution water (ISO Test water) to the stock solution of the test item.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Daphnia magna
- Strain/clone: Straus
- Source: In-house culture
- Age of parental stock (mean and range, SD): Less than 24 hours old.
- Feeding during test: No.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Test temperature:

19.5-20.5 °C

pH:

7.47-7.87

Dissolved oxygen:

8.8-8.9 mg/l

Nominal and measured concentrations:

Nominal concentrations: 0, 1, 2, 4, 8, 16, 32 mg/L
Measured concentrations (initial): 0.907, 1.90, 3.68, 7.69, 15.1, 30.5 mg/L
Measured concentrations (final): 0.813, 1.79, 3.45, 7.39, 14.9, 29.5 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 50 mL glass beakers
- Type (delete if not applicable): coveed with watch glass dishes
- Material, size, headspace, fill volume: glass, 50 mL, - , 20 mL
- Aeration: No.
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 1

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: ISO Test water
- Culture medium different from test medium: No.


OTHER TEST CONDITIONS
- Adjustment of pH: No.
- Photoperiod: Dark.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Mobility

RANGE-FINDING STUDY
- Test concentrations: 0, 0.16, 0.8, 4.0, 20, 100 mg/L (static, 48 hours).
- Results used to determine the conditions for the definitive study: 0, 0, 10, 90 and 100 % immobilization. The expected EC50-value (48 hours) was between 4 and 20 mg/L:

Reference substance (positive control):

yes

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

- Behavioural abnormalities: No.
- Mortality of control: No immobilization was observed in control.
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: No.
- Effect concentrations exceeding solubility of substance in test medium: No.

Results with reference substance (positive control):

The reliability of the test conditions was tested with the reference item (positive control) potassium dichromate (K2Cr2O7) in a separate study (R18-1001-008) at 25/26.07.2018. The determined EC50-24h of 1.9 mg/l lies within the range from the inter laboratory test to ISO 6341. So the test conditions were reliable.

Reported statistics and error estimates:

From the determined effects the EC50-, EC20- and EC10-values of the test item after 24 and 48 hours were calculated by non-linear regression. In addition, the NOEC/LOEC of the test item were determined. In both cases the calculation was carried out with the software SigmaPlot 13.

Nominal and measured concentrations:

Nominal concentration of ZnMoO4 (mg/L)	Correspondingdetermined concentration of ZnMoO4		Average of the determined concentration of Zn
	at 0 hours (mg/L)	at 48 hours  (mg/L)	at 0 hours (mg/L)	at 48 hours (mg/L)
0	<0.24	<0.24	<0,07	<0,07
1	0.907	0.813	0.263	0.236
2	1.90	1.79	0.551	0.521
4	3.68	3.45	1.068	1.001
8	7.69	7.39	2.231	2.144
16	15.1	14.9	4.387	4.330
32	30.5	29.5	8.847	8.559

Recovery of the nominal concentrations:

Nominal concentration of ZnMoO4 (mg/L)	Recoveryof ZnMoO4
	at 0 hours (%)	at 48 hours (%)
1	90.7	81.3
2	94.9	89.7
4	92.1	86.3
8	96.1	92.4
16	94.5	93.3
32	95.3	92.2

The recovery of the test item was normally between 81 and 96 %. In the measurement the recovery was within the range of ± 20 % of the nominal concentration. Thus it can be assumed that the test item was stable over the test duration. Because the difference between the nominal and the measured concentration was smaller than 20 %, the results below were calculated with the nominal concentrations at the beginning of the test.

Test results:

Test concentration (mg/L)	Number of daphnids	Number of immobilised daphnids		Percentage immobilised daphnids		Percentage immobilised daphnids. Total
		24 h	48 h	24 h	48 h	24 h	48 h
0	5	0	0	0	0	0	0
0	5	0	0	0	0
0	5	0	0	0	0
0	5	0	0	0	0
1	5	0	0	0	0	0	0
1	5	0	0	0	0
1	5	0	0	0	0
1	5	0	0	0	0
2	5	0	0	0	0	0	0
2	5	0	0	0	0
2	5	0	0	0	0
2	5	0	0	0	0
4	5	0	0	0	0	0	0
4	5	0	0	0	0
4	5	0	0	0	0
4	5	0	0	0	0
8	5	0	3	0	60	10	55
8	5	1	2	20	40
8	5	0	3	0	60
8	5	1	3	20	60
16	5	0	4	0	80	25	85
16	5	1	3	20	60
16	5	2	5	40	100
16	5	2	5	40	100
32	5	1	5	20	100	25	95
32	5	2	5	40	100
32	5	1	5	20	100
32	5	1	4	20	80

Calculated effect concentrations after 24 and 48 hours:

	Results after 24 hours			Results after 48 hours
	Concentration (mg/L)	95% Conf. Limit		Concentration (mg/L)	95% Conf. Limit
		Lower	Upper		Lower	Uppper
EC10	8.3	3.6	14.5	4.3	3.4	5.5
EC20	19	12.4	>32	5.4	4.4	6.4
EC50	>32	-	-	8.0	7.1	8.9
NOEC	16	-	-	4	-	-
LOEC	32	-	-	8	-	-

pH and dissolved oxygen at the beginning and at the end of the test:

Test concentration (mg/L)	pH-value		O2-conc. (mg/L)
	0 h	48 h	0 h	48 h
0	7.87	7.85	8.8	8.9
1	7.78	7.76	8.8	8.9
2	7.73	7.75	8.9	8.9
4	7.67	7.73	8.9	8.9
8	7.61	7.69	8.9	8.9
16	7.58	7.66	8.9	8.9
32	7.47	7.66	8.8	8.8

Validity criteria fulfilled:

yes

Remarks:

(in the control <10% of immobilization observed, dissolved oxygen concentration at the end of the test >3mg/L)

Conclusions:

The EC50 was determined to be 8.0 mg/L after 48 hours in Daphnia magna.

Executive summary:

An acute Daphnia immobilization test was performed according to the OECD Guideline 202 (GLP study). Based on preliminary tests, 20 Daphnia magna per dose were (in 4 replicates) were exposed to 0 (control), 1, 2, 4, 8, 16 and 32 mg/L test item for 48 hours under static conditions. The recovery of the test item was normally between 81 and 96 %. In the measurement the recovery was within the range of ± 20 % of the nominal concentration. Thus it can be assumed that the test item was stable over the test duration. Because the difference between the nominal and the measured concentration was smaller than 20 %, the results below were calculated with the nominal concentrations at the beginning of the test. No immobilised daphnids were observed in the control group. The dissolved oxygen concentration at the end of the test was ≥ 8 mg/l in each test concentration. The observed percentage of immobilization at the end of the test was 0% (control), 0% (1 mg/L), 0% (2 mg/L), 0% (4 m/L), 55% (8 mg/L), 85% (16 mg/L) and 95% (32 mg/L). The 48h-EC50 of the test item was found to be 8.0 mg/L.

Description of key information

Short-term toxicity to aquatic invertebrates: Key study: Test method OECD 202. GLP study. The EC50 was determined to be 8.0 mg/L after 48 hours in Daphnia magna.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

8 mg/L