Chlorine dioxide

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:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: No purity provided in the CoA and no batch number provided. The method would have been better run under flow-through conditions considering the potential for loss of chlorine dioxide due to its volatility.

Qualifier:

according to guideline

Guideline:

EU Method C.1 (Acute Toxicity for Fish)

Deviations:

no

GLP compliance:

yes

Remarks:

but no certificate is joined

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
no data

Analytical monitoring:

yes

Details on sampling:

Oxygen, pH, temperature and the test substance concentration were measured daily.

- Concentrations:
- nominal concentrations: 0.009, 0.021, 0.045, and 0.1 mg/L
- measured concentrations: 0.01, 0.02, 0.05, 0.08 mg/L
- Sampling method: samples were analyzed for chlorine dioxide by RBM, with the spectrophotometer HACH and the method supplied by the Sponsor.
- Sample storage conditions before analysis: no data

Vehicle:

no

Details on test solutions:

Some volatility of chlorine dioxide may be expected. Although the test systems were not treated as such, analysis of the fresh test solutions showed that there was low loss during preparation.

Test organisms (species):

Danio rerio (previous name: Brachydanio rerio)

Details on test organisms:

TEST ORGANISM
- Common name: Zebrafish
- Strain: no data
- Source: AQUA, Turin, IT
- Age at study initiation (mean and range, SD): no data
- Length at study initiation (length definition, mean, range and SD): 3 cm
- Weight at study initiation (mean and range, SD): 0.4 g
- Method of breeding: no data
- Feeding during test: NO
- Food type:
- Amount:
- Frequency:

ACCLIMATION
- Acclimation period: 2 wks before start of test. All fish were exposed (in a glass aquarium) to water.
- Acclimation conditions (same as test or not): in water , from municipal water main system, at 22°C, pH: 7.2, Hardeness: 21 mg/L of CaCO3, [O2]: 8.1 mg/L
- Type and amount of food: Mangine SERA (Aquaristik GmbH, batch CH 09-3)
- Feeding frequency: daily
- Health during acclimation (any mortality observed): no mortality was recorded after 7 days of acclimation

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Post exposure observation period:

no data

Hardness:

no data

Test temperature:

21 - 22 °C

pH:

6.6 - 7.1

Dissolved oxygen:

7.7 - 9.0

Salinity:

not applicable

Nominal and measured concentrations:

Nominal concentrations: 0.009, 0.021, 0.045 and 0.1 mg/L

Measured concentrations at t = 0 h: 0.01, 0.02, 0.05 and 0.08 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: glass beakers
- Type (delete if not applicable): open
- Material, size, headspace, fill volume: 5 L
- Aeration:no data
- Type of flow-through (e.g. peristaltic or proportional diluter): no data
- Renewal rate of test solution (frequency/flow rate): no data
- No. of organisms per vessel: 7
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1
- No. of vessels per vehicle control (replicates): not applicable
- Biomass loading rate: no data

OTHER TEST CONDITIONS
- Adjustment of pH:
- Photoperiod: 16:8
- Light intensity: no data

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2.2
- Range finding study
- Test concentrations:
- nominal concentrations: 0.009, 0.021, 0.045, and 0.01 mg/L
- measured concentrations: 0.01, 0.02, 0.05, and 0.08 mg/L

Reference substance (positive control):

no

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

0.049 mg/L

Nominal / measured:

meas. (TWA)

Basis for effect:

mortality (fish)

Remarks on result:

other: 95 % confidence limits 0.04 – 0.061 mg/L

Duration:

72 h

Dose descriptor:

LC50

Effect conc.:

0.049 mg/L

Nominal / measured:

meas. (TWA)

Basis for effect:

mortality (fish)

Remarks on result:

other: 95 % confidence limits 0.04 – 0.061 mg/L

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

0.021 mg/L

Nominal / measured:

meas. (TWA)

Basis for effect:

mortality (fish)

Remarks on result:

other: 95 % confidence limits 0.01 – 0.04 mg/L

Duration:

96 h

Dose descriptor:

LC0

Effect conc.:

0.009 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

LC100

Effect conc.:

0.072 mg/L

Nominal / measured:

meas. (TWA)

Basis for effect:

mortality (fish)

Details on results:

The concentration causing no mortality was lower than 0.009 mg/L. The lowest concentration causing 100% mortality was 0.100 mg/L. In the fish treated at 0.045 and 1.00 mg/L the only sign of abnormality observed was decreased escape reflex that appeared at the 24 h observation until the 72 observation in the fish (in fish treated with 0.045 mg/L. In animals treated at 0.009 and 0.021 mg/L the only sign of abnormality observed was decreased escape reflex that appeared at the 72 h observation in those treated at 0.009 mg/L. In both the treated groups this sign lasted until the end of the study. The study was performed taking into account the actual content of the stock solution of chlorine dioxide. The toxicity values can therefore be expressed as referring to the 100% ClO2 and to the solution at the nominal concentration of 0.2%. The LC50 at 24 h was not calculable.

Results with reference substance (positive control):

Not applicable

Reported statistics and error estimates:

no data

Sublethal observations / clinical signs:

Table A7_4_1_1(1)-5:        Mortality data

Test-Substance Concentration nominal [mg/l]	Mortality
	Number     24 h          48 h          72 h          96 h				Percentage     24 h         48 h          72 h           96 h
0.0	0/7	0/7	0/7	0/7	0	0	0	0
0.009	0/7	0/7	0/7	1/7	0	0	0	14
0.021	0/7	0/7	0/7	3/7	0	0	0	43
0.045	0/7	1/7	1/7	4/7	0	14	14	57
0.100	4/7	7/7	7/7	7/7	57	100	100	100

Table A7_4_1_1(1)-6:        Effect data

	48 h [mg/l]^1	95 % c.l.	96 h [mg/l]^1	95 % c.l.
LC0	Not stated	Not stated	0.009 (n)	Not stated
LC50	0.054 (n)	Not stated	0.030 (n)	Not stated
LC100	Not stated	Not stated	0.100 (n)	Not stated

¹ effect data are based on nominal (n) concentrations

Validity criteria fulfilled:

no

Remarks:

no reference substance was tested

Conclusions:

96 h LC50 = 0.021 mg/L (based on the TWA)

Executive summary:

Acute toxicity test was conducted on zebrafish, Danio rerio, to assess effects of chlorine dioxide. The experiment was realized under GLP conditions, and following C.1 EEC Guideline. 4 measured concentrations were tested, with 7 fish exposed to each ones: 0.01, 0.02, 0.05, and 0.08 mg/L of chlorine dioxide. LC50(96h) = 0.030 mg/L of 100 % ClO2; i.e. 0.015 g/L of 0.2% ClO2

Description of key information

Based on results from Gnemi (1996), an LC50(96h) of 0.021 mg/L was determined for chlorine dioxide on the zebrafish, Danio rerio. Chlorine dioxide is highly acutely  toxic to fish, it has a short half-life in the environment following use, and there is no direct release of the active substance to aquatic systems. Chlorine dioxide in aqueous solution reacts rapidly, abiotically with organic matter and oxidisable metals, generating chlorite, chlorate and ultimately chloride as dominant species. Under the conditions of use, no chlorine dioxide is expected to be found in the environment, however the principal decomposition products, chlorite, chlorate and chloride will be. Therefore, supporting studies concerning these substances (except chloride) have also been included in this section such that their toxicity and ultimately risk can be characterised in the CSR.  

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Dose descriptor:

LC50

Effect concentration:

0.021 mg/L

Additional information

One acute toxicity study valid was found in Chlorine dioxide for zebrafish Danio rerio (Gnemi 1996, according to C.1 EEC Guideline). Two acute toxicity studies valid were used in Sodium chlorite for sheepshead minnow Cyprinodon variegates (Ward and Boeri 1991, according to EPA OPP 72 -1; Yurk 1994, according to EPA-FIFRA 72 -3). Finally, two acute toxicity studies valid from the same authors (Ward and Boeri 1991, according to EPA OPP 72 -1 and Ward and Boeri 1991, EPA-FIFRA 72 -3 severally) were used in Sodium chlorate for rainbow trout Oncorhynchus mykiss and sheepshead minnow, respectively.

Based on results from Gnemi (1996), LC50(96h) = 0.021 mg/L of chlorine dioxide on zebrafish. Chlorine dioxide is highly acutely toxic to fish. It has a short half-life (seconds to minutes) in the environment, and there is no direct release of the active substance to aquatic systems. Chlorine dioxide in aqueous solution reacts rapidly, abiotically with organic matter and oxidisable metals, generating chlorite, chlorate and ultimately chloride as dominant species. Under the conditions of use, no chlorine dioxide is expected to be found in the environment, however the principal decomposition products, chlorite, chlorate and chloride will be.

For sodium chlorite the two lowest 96 h LC50s for fish were found at 78 mg/L of chlorite and 55.9 mg/L of chlorite (Ward 1991 and Yurk 1994 respectively). For sodium chlorate 96 h LC50s for fish > 1000 mg/L were observed.