Chlorine dioxide

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

yes

Remarks:

No reference substance was tested

Principles of method if other than guideline:

not applicable

GLP compliance:

yes

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:

Samples were taken after 0, 24, 48 and 72 h.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method:
- Eluate:
- Differential loading:
- Controls:
- Chemical name of vehicle (organic solvent, emulsifier or dispersant):
- Concentration of vehicle in test medium (stock solution and final test solution(s) including control(s)):
- Evidence of undissolved material (e.g. precipitate, surface film, etc):

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: Green algae
- Strain: no data
- Source (laboratory, culture collection): American Type Culture Collection 22662
- Age of inoculum (at test initiation):
- Method of cultivation: in a chamber with a temperature range of 23 +- 2°C, and continuous uniform illumination of 6000 L/ux in the spectral range 400-700 nm.

ACCLIMATION
- Acclimation period: no data
- Culturing media and conditions (same as test or not): no data
- Any deformed or abnormal cells observed: no data

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Post exposure observation period:

no data

Hardness:

no data

Test temperature:

23 ± 2 °C

pH:

7.1 - 8.6

Dissolved oxygen:

no data

Salinity:

not applicable

Nominal and measured concentrations:

Nominal concentrations: 0.022, 0.048, 0.106, 0.234 and 5.15 mg/L

Measured concentrations (at t = 0 h): 0.02, 0.03, 0.08, 0.26 and 0.50 mg/L
Measured concentrations (at t = 72 h): Not determined

Details on test conditions:

TEST SYSTEM
- Test vessel: glass beakers
- Type (delete if not applicable): open
- Material, size, headspace, fill volume: 500 ml of capicity, filled with 100 ml of solution
- Aeration: no
- Type of flow-through (e.g. peristaltic or proportional diluter): no data
- Renewal rate of test solution (frequency/flow rate): no data
- Initial cells density: 10^4 cells/ml
- Control end cells density: cell density was determined at 24, 48, and 72 hours after the start of the study.
- No. of organisms per vessel: 10^6 cells per beaker
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6
- No. of vessels per vehicle control (replicates): not applicable

GROWTH MEDIUM
- Standard medium used: yes
- Detailed composition if non-standard medium was used: not applicable

OTHER TEST CONDITIONS
- Sterile test conditions: yes/no
- Adjustment of pH: no data
- Photoperiod: no data
- Light intensity and quality: no data
- Salinity (for marine algae): not applicable

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations:counting chamber
- Chlorophyll measurement: no data

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2.2
- Justification for using less concentrations than requested by guideline: not applicable
- Range finding study
- Test concentrations: 0.022, 0.048, 0.106, 0.234, and 0.515 mg/L

Reference substance (positive control):

no

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

0.246 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

act. ingr.

Remarks:

100 %

Basis for effect:

growth rate

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

1.35 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

act. ingr.

Remarks:

100 %

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

1.096 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

act. ingr.

Remarks:

100 %

Basis for effect:

growth rate

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

0.047 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

act. ingr.

Remarks:

100 %

Basis for effect:

biomass

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

0.258 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

act. ingr.

Remarks:

100 %

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.324 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

act. ingr.

Remarks:

100 %

Basis for effect:

biomass

Duration:

24 h

Dose descriptor:

NOEC

Effect conc.:

0.02 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

act. ingr.

Remarks:

100 %

Basis for effect:

growth rate

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

0.02 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

act. ingr.

Remarks:

100 %

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.02 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

act. ingr.

Remarks:

100 %

Basis for effect:

growth rate

Duration:

24 h

Dose descriptor:

NOEC

Effect conc.:

< 0.02 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

act. ingr.

Basis for effect:

biomass

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

0.02 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

act. ingr.

Remarks:

100 %

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.02 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

act. ingr.

Remarks:

100 %

Basis for effect:

biomass

Details on results:

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 a referring to the 100% ClO2 and to the solution at the nominal concentration of 0.2%. At 72 h, the EbC50 for ClO2 100% was 0.324 mg/L. The 72 h NOEC (d) was 0.02mg/L, the ErC50 was 1.096 and the NOEC (r) was 0.02 mg/l.

Results with reference substance (positive control):

Not applicable

Reported statistics and error estimates:

EC50 and statistical limits were calculated usingthe modified probit method set up by the Flemish Institute for Technological Research (VITO)

Table A7_4_1_3(1)-4:        Cell concentration data

Chlorine Dioxide Concentration (mg/L)	Mean Cell Density 10^4 cells/ml
	T(0)0	T(1)24	T(n-1)48	T(n)72
0	1.6	5.23	16.17	68.67
0.02	1.6	3.9	17	82.67
0.03	1.6	3.37	12	53
0.08	1.6	3.1	11.33	56
0.26	1.6	3.1	9.6	52
0.50	1.6	2.6	9.4	18

Validity criteria fulfilled:

no

Remarks:

No reference substance was tested

Conclusions:

At 72 h, the EbC50 for ClO2 100% was 0.324 mg/L. The 72 h NOEC (d) was 0.02mg/L, the ErC50 was 1.096 and the NOEC (r) was 0.02.

Executive summary:

Effect of chlorine dioxide on inhibition growth was tested on Selenastrum capricornutum, under GLP and following C.3 EEC Guidelines. 5 different concentrations have been tested during 72 hours: 0.022, 0.048, 0.106, 0.234, and 0.515 mg/L nominal concentration of chlorine dioxide. Experiment was conducted with 3 replicates for each concentration tested, and 6 replicates for controls. EbC50(72h) = 0.324 mg/L for chlorine dioxide 100% i.e. 0.162 g/L for chlorine dioxide 0.2%, and NOEC(b) = 0.02 mg/L

for chlorine dioxide 100% i.e. 0.10 g/L for chlorine dioxide 0.2%. ErC50(72h) = 1.096 mg/L for chlorine dioxide 100% i.e. 0.548 g/L for chlorine dioxide 0.2%, and NOEC(r) = 0.02 mg/L for chlorine dioxide 100% i.e. 0.010 g/L for chlorine dioxide 0.2%

Description of key information

Based on results from Gnemi (1996), the ErC50(72h) and NOECr(72h) were 1.096 mg/L and 0.02 mg/L as chlorine dioxide, respectively, on the freshwater algae, Selenastrum capricornutum. Chlorine dioxide reacts rapidly in aqueous solution degrading to chlorite and chlorate as dominant species under environmental conditions. In the absence of oxidisable substances, and in the presence of pH > 9, chlorine dioxide dissolves in water and decomposes with the slow formation of  chlorite and chlorate ions.

Key value for chemical safety assessment

EC50 for freshwater algae:

1.096 mg/L

EC10 or NOEC for freshwater algae:

0.02 mg/L

Additional information

One valid acute toxicity study was found on Chlorine dioxide for freshwater algae Selenastrum capricornutum (Gnemi 1996; according to EU Method C.3). Based on results from Gnemi (1996), EC50(72h) = 1.096 mg/L of chlorine dioxide on freshwater algae.

Toxicity of the substance has been tested on Macrocystis pyrifera, in a 48h acute-static test, following US EPA Guideline EPA-600 -R-95 -136. The results demonstrated a NOEC of 0.143 mg/L of chlorine dioxide for germination and germ tube length criteria; an EC50(48h) = 0.202 mg/L for germination, and an EC50(48h) = 0.206 mg/L for germ tube length criterion.

Chlorine dioxide reacts rapidly degrading to chlorite and chlorate as dominant species.

Three valid acute toxicity studies were included for Sodium chlorite, two on the same freshwater algae species (Ward et al. 1991, according to EPA-FIFRA Guideline 122 -2; Van Wijk 1998, no standard guideline), and one on the marine algae Phaeodactylum tricornutum (Gyimesi 2008, according to ISO 10253).

 

Sodium chlorite studies on freshwater algae demonstrated an EC50(96h) = 0.75 mg/L as chlorite and 0.8 mg/L as chlorite depending the study (Ward 1991; Van Wijk 1998), on marine algae, the EC50(72h) = 11.8 mg/L as chlorite.

Finally, three acute toxicity studies were included for Sodium chlorate, two on Guideline test species with EC50s >100 mg/L and one on the marine microalgae Nitzschia closterium (Stauber 1998) although this study was not performed using a standard test protocol and is included only to characterise the relationship between chlorate and nitrate concentrations and its role in algae toxicity.