Sodium chlorate

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study generated according to a valid and internationally accepted testing guideline and was performed under GLP.

Qualifier:

according to guideline

Guideline:

OECD Guideline 211 (Daphnia magna Reproduction Test)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Samples were taken on the first day of the study on preparation and just before changing.
- Further samples were taken weekly.
- Samples were taken in duplicate and were frozen until analysis.

Vehicle:

no

Details on test solutions:

- Procedures: To prepare the stock solutions, approximately 5 or 10 g of test substance was weighed and dissolved directly in 500 or 1000 ml,
respectively of M4 medium.
- The obtained preparations were agitated mechanically for 24 h in an attempt to completely dissolve the test substance.
- The pH of each stock solution was between 6.8 and 8.3.
- The pH was adjusted to between 7.6 and 7.8 with 1 M HCI or NaOH (reagent grade) when necessary.
- A fresh stock solution was prepared for each solution change.

Test organisms (species):

Daphnia magna

Details on test organisms:

Daphnia magna STRAUS-clone 4
- Source/supplier: AquaSense, Amsterdam, The Netherlands
- Breeding method: According to the relevant SOP
- Age: less than 24 hours
- Feeding: Chlorella vulgaris
- Feeding during test: yes, between 0.1 and 0.2 mg of carbon per daphnid per day, from day 8

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Hardness:

133-138 °dH

Test temperature:

20.2-21.4 °C

pH:

7.6-8.2

Dissolved oxygen:

8.0-9.1 mg/l

Nominal and measured concentrations:

- Nominal: 0, 12.8, 32, 80, 200 and 500 mg/L
- Measured: The measured concentrations were within 20% of the nominal concentrations and therefore the nominals were used for all
statistical evaluation.

Details on test conditions:

DILUTION WATER:
- Elendt M4 medium
- Aeration: yes
- Ca/Mg ratio: 4:1
- Na/K ratio: 10:1
- pH: 8.0 ± 0.5
- Holding water: same as dilution water
- Renewal of test solution: every two to three days
- Exposure vessel type: 50 ml glass beakers
- Number of replicates, individuals per replicate: 10, 1
- Conductance: in control 609-663 µs/cm, in 500 mg/L 1099-1145 µs/cm
- Adjustment of pH: no
- Intensity of irradiation: ambient light provided by fluorescent tubes
- Photoperiod: 16 hours photoperiod daily

Reference substance (positive control):

no

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

>= 500 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: reproduction, weight and length

Details on results:

- Unhatched eggs: None found
- Length and weight of surviving animals: No signifacnt difference between the concentrations.
- Numbers of dead young: At all concentrations except the control at least one and at most five neonates were found to be dead.

The mortality appeared to be concentration related but was insignificant compared to the living neonates. Immobilization: one daphnid died in 80 mg/L on day 15.
- EC50 for mortality of adults and for reproduction could not be determined due to insufficient mortality in the test concentrations.

CONTROL:
- Number/percentage of animals showing adverse effects: No mortality occurred
- Average number of juveniles per parent: 103.3 after 21 days

Reported statistics and error estimates:

Weight data were tested for normality using Chi-square test and Barlett's test for homogeneity of variance.
ANOVA was performed on the number of living neonates per parent using Bonferroni t-test and verified with the Dunnett's test.
All other parameters were not tested because the result in the control group was lower than in the test concentrations.

Time to first brood: Number of animals having the first brood on a given day.

Conc (mg/l)	Day of first brood
	8	9	10	11	12	13
0	7	3
12.8	9		1
32	6	3	1
80	6	3		1
200	9	1
500	3	2	4			1

 

Number of juveniles produced: No significant difference was found in total and mean number of juveniles between the concentrations.  

 

Average total number of living juveniles produced per parent per concentration:

Conc (mg/l)	no. juveniles/parent
0	103.3
12.8	109.8
32	120.7
80	121.7
200	126.5
500	108.6

 

Validity criteria fulfilled:

yes

Conclusions:

Test conducted under GLP with analysis, analysis certificate was present and to relevant guideline was used. This study can be considered reliable
without restrictions.
The NOEC for reproduction, weight and length is equal to or greater than 500 mg/l.

Executive summary:

The purpose of this study was to assess the toxicity of the test substance dissolved in fresh water, on the reproductive efficacy of Daphnia magna STRAUS - clone 4, in a 21-day semi-static test complying with the OECD Guideline No. 211 , 21st September 1998.

The test criterion of toxicity used was reproductive capacity expressed as the number of neonates per daphnid per day.

The nominal concentrations used in the study were as follows: 0, 12.8, 32.0, 80.0, 200 and 500 mg/l

Analytical determinations of the test solutions were made on six occasions during the test. The concentrations were found to remain stable to within ±20% of the nominals. The nominal concentrations were used to calculate the effect concentrations.

The validity criteria were respected: No mortality occurred in the control group over the test period.

The average number of juveniles per parent in the control was 103.3 after 21 days The No Observed Effect Concentration (NOEC) is determined as the concentration used in the study that is immediately below the Lowest Observed Effect Concentration (LOEC), the latter derived statistically from the data, where possible, using the appropriate statistical test.

Reproductive output and length of adults at the end of the study were lower in the control than in any other concentration tested and was therefore not evaluated statistically. Weight data were found to be normally distributed and homogeneous. Using Dunnett’s and Bonferroni-t tests, the lowest Observed Effect Concentration (LOEC) based on weight was found to be greater than 500 mg/l. Based on these statistical results the NOEC for reproduction, weight and length is 500 mg/l.

The EC50 for adult mortality and for reproduction could not be determined due to insufficient mortality in any of the test concentrations.

Reference 2

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

31 May 2010 until 4 June 2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: well conducted study according to standard protocol with chemical analyses and GLP.

Qualifier:

according to guideline

Guideline:

other: ISO/DC 20666

Deviations:

yes

Remarks:

test duration is 96h and performed in continuous light

Principles of method if other than guideline:

The toxicity test was conducted with 8 wells with 1 animal in each for each test concentration, 16 control wells were used for control. The test animals were less than 24 hours old. Newly hatched rotifers were selected based on shape and size. A 24 Multiwell plate was used for incubation. A concentrated culture of Nannochloropsis oceanica and Tetraselmis suecica were added to each well at the start to give an algal cell concentration of >3x10E6 cells/ml.

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Sodium Chlorate levels were analysed in the test solution before addition of test organisms and feed algae suspension and at the end of the test.

Vehicle:

no

Details on test solutions:

The test concentrations were prepared by diluting a stock solution of 1000 mg/l of Sodium Chlorate with appropriate amount of aged sea water.

Test organisms (species):

other: brachionus plicatilis

Test type:

static

Water media type:

saltwater

Limit test:

no

Total exposure duration:

96 h

Test temperature:

20.1-20.5°C

pH:

7.89-8.16

Dissolved oxygen:

>7.7 mg/L

Nominal and measured concentrations:

Sample nominal Measured Sodium Chlorate % of nominal
10 mg/l initial 8.2 82
10 mg/l end 6.6 66
22 mg/l initial 19.3 88
22 mg/l end 16.8 76
46 mg/l initial 42 92
46 mg/l end 35 77
100 mg/l initial 99 99
100 mg/l end 92 92
220 mg/l initial 218 99
220 mg/l end 185 84
460 mg/l initial 471 102
460 mg/l end 392 85
1000 mg/l initial 1031 103
1000 mg/l end 865 86

Details on test conditions:

TEST SYSTEM
- Test vessel: 24 Multiwell plate
- No. of organisms per vessel: 1
- No. of vessels per concentration (replicates): 8
- No. of vessels per control (replicates): 16

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Aged sea water was used as control medium and for dilution of Sodium Chlorate. The sea water was sieved (1 μm) in order to exclude particles and other organisms.
- Culture medium different from test medium: No

OTHER TEST CONDITIONS
- Adjustment of pH: No
- Photoperiod: continuous light
- Light intensity: not known

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : number of offspring using a low power stereoscopic microscope, mortality

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

596 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks on result:

other: 95%CL 417-1215 mg/L

Key result

Duration:

96 h

Dose descriptor:

EC10

Effect conc.:

21.9 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks on result:

other: 95%CL 6.8-55.6 mg/L

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

46 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Details on results:

Chemical analysis
Initial test concentrations are measured to be between 82 and 103 % of nominal. After test end the test solutions were collected and filtered before chemical analysis. Test concentrations were then measured to be between 66 and 92 % of nominal. Most test concentrations showed a decrease of approximately 15 % from start to end.
Almost all mean concentrations were > 80% of the nominals. Only the lowest test concentration was below 80% (74%), but this is not a critical concentration, therefore nominals were used for effect calculations.

Results with reference substance (positive control):

EC50 = 5.6 mg/L for growth inhibition.

Reported statistics and error estimates:

NOEC was determined using the Dunnett’s test with JMP statistical package of SAS institute (1989-1997). EC10 and EC50 values were determined using logistic regression analysis.

Number of offspring after 96 hours exposure to Sodium Chlorate.

Replicate no	Control	1000 mg/L	460 mg/L	220 mg/L	100 mg/L	46 mg/L	22 mg/L	10 mg/L
1	7	4	3	5	4	7	6	7
2	7	2	3	5	3	7	7	7
3	6	2	3	3	4	6	8	8
4	6	3	4	5	7	5	7	7
5	7	5	6	3	6	5	6	7
6	6	2	5	4	3	5	6	8
7	6	2	4	3	5	6	7	8
8	6	2	7	5	4	4	4	6
9	7
10	6
11	8
12	8
13	7
14	7
15	9
16	8
Total	111	22	35	33	36	45	51	58
Average	6.9	2.8	4.4	4.1	4.5	5.6	6.4	7.3
% inhib	0.0	60.4	36.9	40.5	35.1	18.9	8.1	-4.5

Validity criteria fulfilled:

yes

Conclusions:

The test was well conducted according to standard protocol with chemical analysis and GLP.
Sodium chlorate is not very toxic to the marine rotifer Brachionus plicatilis.

Executive summary:

The effect of Sodium Chlorate on the reproduction to the marine rotatoria Brachionus plicatilis has been investigated. The test was performed according to ISO/DC 20666- Water quality – Determination of the chronic toxicity to Brachionus calcyflorus in 48h. The test concentrations were 10, 22, 46, 100, 220, 460 and 1000 mg/l of Sodium Chlorate. Aged seawater was used as control in the test.

The test was performed with 8 replicate vessels with 1 animal in each, for each test concentration and 16 control replicate vessels. The vessels were incubated for 96 hours at 20 ±1 °C. Mortality and number of offspring were recorded after 96 hours.

There was a dose dependent reduction in reproduction observed for B. plicatilis, when exposed to Sodium Chlorate. Statistical assessment indicate a NOEC of 46 mg/l Sodium Chlorate. EC50 was estimated to be 596 mg/l Sodium Chlorate. Mortality of parent rotatoria was not observed at any concentration.

The test indicates that high concentration of Sodium Chlorate exerts a reproductive inhibition on B. plicatilis.

Description of key information

Two long-term studies on aquatic invertebrates are available and were performed on sodium chlorate.

The NOEC for aquatic invertebrates Daphnia magna is equal or greater than 500 mg/l sodium chlorate.

The EC10 for marine rotatoria Brachionus plicatilis is  21 mg/l sodium chlorate.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

NOEC

Effect concentration:

>= 500 mg/L

Marine water invertebrates

Marine water invertebrates

Dose descriptor:

EC10

Effect concentration:

21 mg/L

Additional information

One chronic study with sodium chlorate for the freshwater aquatic invertebrates Daphnia magna was found. The test was performed according to OECD guideline 211 and GLP conditions. Chemical analyses showed that the test substance concentrations were stable and close to nominal concentrations. The test was therefore considered valid without restrictions. The NOEC for freshwater aquatic invertebrates is equal or greater than 500 mg/l sodium chlorate.

In addition, One long-term study (valid without restrictions) is available for the rotifer Brachionus plicatilis with sodium chlorate. This study by Tobiesen (2010b) was performed according to standard guideline with GLP and chemical analysis of the test substance. B. Plicatilis turned out to be the most sensitive marine species with an EC₁₀of 21 mg/l sodium chlorate.