Diquat dibromide

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

Study period:

5 Jan 1989 to 31 Jan 1989

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 204 (Fish, Prolonged Toxicity Test: 14-day Study)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Samples of the test solutions were taken for analysis from the middle of each test vessel on days 1, 2, 3, 7, 9, 13, 15 and 21.

Vehicle:

no

Details on test solutions:

Glass jars of 2 L capacity were filled with 1 L of distilled water. The amounts of the test substance concentrate required to provide nominal stock concentrations of 126, 70.6, 40.3, 22.7, 12.6 and 7.06 g/L in 1.6 L of distilled water were added to the glass jars. The solutions were then made up to 1.6 L with distilled water and fed to the system. The stock solutions were fed to the system by a series of peristaltic pumps and the dilution water was supplied using a capillary flow control system. The stock solutions of the cast material and freshwater diluent were passed to a series of glass mixing chambers where magnetic stirrers were used to ensure mixing before the test solutions passed into the fish exposure vessels. The mean dilution ratio of the stock solutions to dilution water was 1:1043 (nominal value = 1:1000) in all concentrations.

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM
- Common name: Rainbow trout
- Obtained date: 10 November 1988
- Food type: During the test the fish were fed with commercial diet.
- Feeding frequency: During the test the fish were fed at a rate of 2.0% of the mean body weight per day. The mean weight of the fish was determined by bulk weighing each test population on days 0, 14 and 21.

ACCLIMATION
- Acclimation period: 3 weeks
- Acclimation conditions: The fish were held in glass aquaria under daylight and artificial lighting and at 15 ± 1 °C.
- Health during acclimation: No sickness, injury or abnormality and less than 1% mortality was observed in the fish in the 3 weeks prior to the test. The last medication given to the fish was a 1 ppm treatment of malachite green on 25 November 1988 (6 weeks prior to the test).

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Hardness:

46.3 - 57.3 mg CaCO3/L

Test temperature:

15 ± 2 °C

pH:

7.4 - 7.8

Dissolved oxygen:

9.8 - 10.4 mg O2/L

Conductivity:

120 - 150 µs/cm

Nominal and measured concentrations:

- Nominal concentration: 0 (negative control), 1.5, 2.6, 4.7, 8.4, 14.7 and 26.2 mg test substance cation/L
- Measured concentration: < LOQ (negative control), 1.4, 2.4, 4.8, 8.4, 13.3 and 23.0 mg test substance cation/L, respectively. See Table 1 in 'Any other information on materials and methods incl. tables'.

Details on test conditions:

TEST SYSTEM
- Test vessel: 55 L glass vessel
- Aeration: No
- Type of flow-through: Peristaltic pump
- Flow rate: 250 mL/minute (95% exchange of the test solutions was calculated to occur within 9.0 hours)
- No. of organisms per vessel: 10
- No. of vessels per concentration: 2
- No. of vessels per control: 2

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The dilution water was dechlorinated tap water supplied from a 100 m3 reservoir with an average retention time of 24 hours. After dechlorination with sodium thiosulphate, the water was passed through activated carbon, filtered to remove particulate material and preheated to 15 °C. Calibration of the dilution water and toxicant flow rate was undertaken daily for the first three days and then 3 times per week. The dilution water and toxicant flow rates were measured by collecting into measuring cylinders for 1 and 4 minutes respectively.
- Intervals of water quality measurement: The dissolved oxygen, pH and temperature were measured in each test vessel daily for the first 3 days and then 3 times per week until the end of the study. The flow rates of the dilution water and concentrated test material were measured with the same frequency. In addition, the water hardness, conductivity, and the free and total available residual chlorine content of the dilution water were determined on every weekday.
- Resudual chlorine measurement: The available free and total residual chlorine were determined separately by a colorimetric method using a Lovibond comparator based upon the reaction between the various chlorine species and NN-diethyl-p-phenylene diamine(DPD) to form a stable pink complex. Interference from metal ions was suppressed using EDTA as a chelating agent. The combined available residual chlorine was calculated by subtracting the free available from the total available residual chlorine.

OTHER TEST CONDITIONS
- Photoperiod: 16 hours light and 8 hours darkness

EFFECT PARAMETERS MEASURED
Observations of the symptoms of toxicity and mortalities were made daily.

Reference substance (positive control):

no

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

11.39 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

other: pure test substance

Basis for effect:

mortality (fish)

Remarks on result:

other: Recalculated value, expressed as pure substance, see ‘Any other information on results incl. tables’ for respective calculation

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

6.1 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

other: test substance cation species

Basis for effect:

mortality (fish)

Remarks on result:

other: Original value presented in study

Remarks:

95% C.L.: 3.9 - 8.9 mg/L

Details on results:

An overview of the results is provided in Table 2 and Table 3 in 'Any other information on results incl. tables'
Following 24 hours of exposure, all fish survived in the negative control, 1.4 and 2.4 mg test substance cation/L treatment groups. The mortality of 10, 80, 100 and 100% was observed in the 4.8, 8.4, 13.3 and 23.0 mg/L mean measured concentrations, respectively. Significant symptoms of toxicity were observed in ≥ 4.8 mg/L treatments.

Sublethal observations / clinical signs:

Table 2. Percentage of mortality during the test

Nominal concentration of the test substance concentrate (mg/L)	Nominal concentration of the cation (mg/L)	Mean measured concentration of the cation (mg/L)	Cumulative percentage mortality observed
			Day 4	Day 7	Day 10	Day 14	Day 21
126	26.2	23.0	100	100	100	100	100
70.6	14.7	13.3	100	100	100	100	100
40.3	8.4	8.4	80	100	100	100	100
22.7	4.7	4.8	10	90	90	90	100
12.6	2.6	2.4	0	0	20	20	20
7.06	1.5	1.4	0	0	0	0	0
negative control	-	-	0	0	0	0	0

 

Table 3. Symptoms of toxicity observed

Day	Nominal concentration of the cation (mg/L)
	26.2	14.7	8.4	4.7	2.6	1.5
1	A	A	A	A	A	A
2	C/2,3,4,6,8	C/2,4,7	A	A	A	A
3	TD	C/2,3,4,5,6	C/2,3,4,5,6,8	C/3,5	A	A
4	-	TD	C/2,3,4,5,6	C/1,3,5	A	A
5	-		TD	C/2,3,5	A	A
6	-	-	-	C/1,3,4,5,6	C/1,5	A
7	-	-	-	C/2,5,8	C/1,3,4,5	A
8	-	-	-	C/2,6,7	C/1,3,4,5,6	A
9	-	-	-	C/2,5,7	C/1,3,4,5,6	A
10	-	-	-	C/2,5,7	C/1,3,4,5,6	A
11	-	-	-	C/2,5,7	C/1,3,4,5,6	A
12	-	-	-	C/2,5,7	C/1,3,4,5,6	A
13	-	-	-	C/2,5,8	C/1,4,5,6,7	A
14	-	-	-	C/2,6,7	B/1,4,5,6	A
15	-	-	-	C/2,6,7	B/1,4,5,6	A
16	-	-	-	TD	B/1,4,5,6	A
17	-	-	-	-	B/1,4	A
18	-	-	-	-	B/1,4	A
19	-	-	-	-	B/1,4	A
20	-	-	-	-	B/4	A
21	-	-	-	-	B/4	A

A = No significant effect. 10% or less of test population dead or exhibiting symptoms of toxicity

B = Partial effect. Between 11% and 30% of test population dead or exhibiting symptoms of toxicity

C = Significant effect. More than 30% of test population dead or exhibiting symptoms of toxicity

TD - Terminated

1 = poor feeding response

2 = no feeding response

3 = quiescent

4 = dark discoloured

5 =loss of balance

6 = sounding

7 = rapid breathing

8 = surfacing

Calculation of key result

The original effect levels were expressed as cation species of the registered substance. The key effect levels are re-calculated and corrected to include the counterion species by multiplying with 1.868 (344.0 g/mol molecular weight of registered substance divided by 184.2 g/mol molecular weight of cation species).:

1.868 x 6.1 mg/L = 11.39 mg/L

Validity criteria fulfilled:

yes

Conclusions:

The 96 hour LC50 was determined to be 6.1 mg cation/L with 95% confidence interval of 3.9 – 8.9 mg/L. This LC50 value is equivalent to 11.39 mg registered substance/L.

Executive summary:

To determine the 96-hour acute toxicity of the test substance to rainbow trout (Oncorhynchus mykiss), the exposure was conducted under flow-through conditions following OECD TG 204. The test was in compliance with GLP criteria. One aquarium, containing ten fish, was established for each nominal treatment level of 1.5, 2.6, 4.7, 8.4, 14.7 and 26.2 mg test substance cation/L, respectively. The mean measured concentration was 1.4, 2.4, 4.8, 8.4, 13.3 and 23.0 mg cation/L, respectively (measured by LC). These concentrations were equivalent to 7.06, 12.6, 22.7, 40.3, 70.6 and 126 mg test material/L.  In addition a negative control was included in the test as well.

These vessels were maintained in 15 ± 2 °C and under 16 hour light and 8 hour dark photoperiod. The exposure was lasted for 21 days with a flow rate approximately 250 mL/min (95% exchange of the test solution within 9 hours). Observations of the symptoms of toxicity and mortalities were made daily. The dissolved oxygen was 9.8 – 10.4 mg O2/L and pH was 7.4 – 7.8. Following 24 hours of exposure, all fish survived in the negative control, 1.4 and 2.4 mg cation/L treatment groups. Mortality of 10, 80, 100 and 100% was observed in the 4.8, 8.4, 13.3 and 23.0 mg cation/L mean measured concentrations, respectively. Significant symptoms of toxicity were observed in ≥ 4.8 mg cation/L treatments. The 96 hour LC50 was determined to be 6.1 mg test cation/L with 95% confidence interval of 3.9 – 8.9 mg/L. This LC50 value is equivalent to 11.39 mg test substance/L.

Description of key information

96-h LC50 = 11.39 mg registered substance/L, Oncorhynchus mykiss, OECD TG 204, Tapp 1989

96-h LC50 = 90.55 mg registered substance/L, Cyprinodon variegatus, EPA 72-3, Nicholson 1987

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Dose descriptor:

LC50

Effect concentration:

11.39 mg/L

Additional information

To determine the 96-hour acute toxicity of the test substance to rainbow trout (Oncorhynchus mykiss), the exposure was conducted under flow-through conditions following OECD TG 204. The test was in compliance with GLP criteria. One aquarium, containing ten fish, was established for each nominal treatment level of 1.5, 2.6, 4.7, 8.4, 14.7 and 26.2 mg test substance cation/L, respectively. The mean measured concentration was 1.4, 2.4, 4.8, 8.4, 13.3 and 23.0 mg cation/L, respectively (measured by LC). These concentrations were equivalent to 7.06, 12.6, 22.7, 40.3, 70.6 and 126 mg test material/L.  In addition a negative control was included in the test as well.

These vessels were maintained in 15 ± 2 °C and under 16 hour light and 8 hour dark photoperiod. The exposure was lasted for 21 days with a flow rate approximately 250 mL/min (95% exchange of the test solution within 9 hours). Observations of the symptoms of toxicity and mortalities were made daily. The dissolved oxygen was 9.8 – 10.4 mg O2/L and pH was 7.4 – 7.8. Following 24 hours of exposure, all fish survived in the negative control, 1.4 and 2.4 mg cation/L treatment groups. Mortality of 10, 80, 100 and 100% was observed in the 4.8, 8.4, 13.3 and 23.0 mg cation/L mean measured concentrations, respectively. Significant symptoms of toxicity were observed in ≥ 4.8 mg cation/L treatments. The 96 hour LC50 was determined to be 6.1 mg test cation/L with 95% confidence interval of 3.9 – 8.9 mg/L. This LC50 value is equivalent to 11.39 mg test substance/L.