Sodium dithionite

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:

read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study with acceptable restrictions, no analytical dose verification

Justification for type of information:

see attachment “Read-across concept – Human Health/Environment - Category approach for Inorganic sulfites/thiosulfates/dithionite" in section 13.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 211 (Daphnia magna Reproduction Test)

Version / remarks:

Cited as EEC Guideline XI/681/86, Draft 4

Principles of method if other than guideline:

The chronic toxicity to the water flea Daphnia magna STRAUS was investigated in a 21 day semistatic test according to EEC Guideline XI/681/86, Draft 4, "Prolonged toxicity study with Daphnia magna: effects on reproduction".

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

- At the beginning of the test and before changing the test solutions a stock solution of the test substance was freshly prepared. A defined amount of the substance was weighed out and suspended directly in the test medium by stirring.
- The nominal concentration of the stock solutions was 100 mg/L.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Source: The clone of Daphnia magna STRAUS used was supplied by Institut National de Recherche Chimique Appliquée, France, in 1978. The daphnids are cultured under standard conditions in the laboratory of ecotoxicology, BASF AG, "Ludwigshafen".
- Age of parental stock: 2-4 weeks
- Age of the animals at the start of the test: 2 -24 h
- Culture conditions: The daphnid tests are performed under the same environmental conditions as the culture itself.
- Feeding during test: During the test daphnids were fed live green algae (Scenedesmus subspicatus, cultured in a synthetic medium) daily. The algae were separated from culture medium by centrifugation, resuspended in daphnid's medium (M4) and daphnids were fed this- concentrate. The algae were stored in a refrigerator (dark, about 4°C) for 8 days (in general, maximum storage for up to 14 days). Through feeding the concentrate (maximum: 0.3 mL/50 mL test solution/day) the test solution was diluted in the worst case (Friday-Monday, 3 feedings) by 0.9 mL (= 1.8%).

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Hardness:

2.2-3.2 mmol/L

Test temperature:

20±2°C

pH:

7.5-8.0

Dissolved oxygen:

> 7 mg/l

Nominal and measured concentrations:

0, 1, 5, 10 mg/l (nominal)

Details on test conditions:

TEST SYSTEM
- Test vessel: Numbered glass beakers, nominal volume 100 mL, covered with numbered glass caps
- Fill volume: 50 mL
- Renewal of test solution: three times per week
- No. of organisms per vessel: 1 parent animal
- No. of vessels per concentration (replicates): 10
- No. of vessels per control (replicates): 10

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: synthetic medium M4
- This synthetic medium has the following properties:
Total hardness 2.20 - 3.20 mmol/L
Alkalinity up to pH 4.3: 0.80 - 100 mmol/L
Molar ratio Ca/Mg: about 4:1
pH value: 7.5-8.5
Conductivity : 550 - 650 µS/cm

OTHER TEST CONDITIONS
- Photoperiod: Artificial Iight, day/night-rhythm = 16 / 8 hours
- Light intensity: About 5 - 6 µE/(m2xS) in the range of 400 - 700 nm

EFFECT PARAMETERS MEASURED
- Reproduction and mortality, daily observation intervals

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

> 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: reproduction rate and mortality

Duration:

21 d

Dose descriptor:

other: LC0

Effect conc.:

> 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Conc. (mg/L)	Survival parent animals (%)	Live young / live parent animal (%)
0	100	108.3
1	100	105.0
5	100	119.2
10	90	107.7

Validity criteria fulfilled:

yes

Remarks:

In the control : - mortality of parent animals up to the end of the test was < 10%. - the mean number of live young per parent animal, which survived the test, was > 60. - the coefficient of variation of the mean number of live young per parent animal, wh

Conclusions:

A chronic invertebrate toxicity test was conducted with the cladoceran D.magna, using sodium disulfite as test compound. A NOEC of >10 mg test item/L was derived and this data point can be used for hazard/effects asessment purposes for sodium disulfite and other sulfite compounds (read-across principles)

Reference 2

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Study period:

1993-11-24 to 1993-12-15

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: guideline study

Justification for type of information:

see attachment “Read-across concept – Human Health/Environment - Category approach for Inorganic sulfites/thiosulfates/dithionite" in section 13.

Principles of method if other than guideline:

Static renewal test according to draft 4 of the EC-guideline XI/681/86

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Concentration of the stock solution: 100 mg/l nominal, freshly prepared at the beginning of the test and before changing the test solution
- Differential loading: no
- Evidence of undissolved material (e.g. precipitate, surface film, etc): no

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Daphnia magna STRAUSS
- Source: Daphnia magna Straus was originally supplied from "Institut National de Recherche Chimique appliquee, France", and has been breeded from 1978 in the Laboratories of BASF.
- Age at study initiation (mean and range, SD): 2 - 24 hours old
- Age of parental stock (mean and range, SD): 2-4 weeks
- Feeding during test: yes, daily, according to a feeding schedule (green algae (Scenedesmus subspicatus, cultured in a synthetic medium))

Test type:

semi-static

Water media type:

freshwater

Total exposure duration:

21 d

Hardness:

2.2-3.2 mmol/l total hardness

Test temperature:

20±2°C

pH:

7.5-8.2

Dissolved oxygen:

> 7.9 mg/l

Nominal and measured concentrations:

0, 1, 5, 10 mg/l (nominal)

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Type (delete if not applicable): closed
- Material, size, headspace, fill volume: glass beakers with caps, nominal volume 100 ml, test volume 50 ml
- Aeration: not during test
- No. of organisms per vessel: 1
- No. of vessels per concentration (replicates): 10
- No. of vessels per control (replicates): 10
- Biomass loading rate: 1/50 (animal/ml)


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: synthetic Medium M4 on the basis of an ultrapure, deionized water. The medium was aerated until saturated with oxygen, and was left to stand for 24 h for stabilization
- Alkalinity: 0.80-1.00 mmol/l (up to pH4)
- Ca/mg ratio: 4:1
- Conductivity: 550-650 uS/cm
- Intervals of water quality measurement: every 24h


OTHER TEST CONDITIONS
- Adjustment of pH: not during test
- Photoperiod: 16:8 L:D
- Light intensity: approximately 5-6 uE/(m2*s) at a wavelenght between 400 and 700 nm


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
mortality, hatching of the young (at the beginning and afterwards daily), pH, oxygen (at every renewal of test solution), temperature (continously)

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

> 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Duration:

21 d

Dose descriptor:

other: LC0

Effect conc.:

> 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Details on results:

see below

Reported statistics and error estimates:

Duncan's multiple range test was used to evaluate potential significant differences among test concentrations and the control.

- In the control and at 10 mg/L the first young were
observed on day 9

- The LC0 (mortality) and the NOEC value for repoduction
after 21 d exposure is based on nominal concentrations,
because of the decomposition of sodium dithionite in water
 
- The quality criteria of the control (mortality of parent animals <=  20%, average of >= 60 juveniles per surviving control adult, coefficient  of variation of the mean number of surviving juveniles <= 25%) were  achieved.

- Summary of the effect of the test substance on the reproduction of  Daphnia magna. The values gien are the mean, cumulative values for parent  animals which survived the exposure for 21 days:

Conc.   survival of     live young per   dead young per
(mg/L)  parent animals  live parent an.  live parent animal
            (%)             (n)                (n)
  0         100            108.3                0
  1         100             99.3                0
  5         100            116.3                0
 10         100            116.9                0

Conc.  aborted eggs per
(mg/L) live parent animal
            (n)
  0          0
  1          0
  5          0
 10          0

- Mean total number of live young per parent animal, which survived the  exposure for 21 days, at various concentrations of the test substance:

conc.  live young per
(mg/L) parent animal 
       (n; mean value)    
  0      108.3
  1       99.3
  5      116.3
 10      116.9

- Survival of parent animals at various concentrations of the test  substance during the test. The values given are the total number of live  parent animals at the corresponding concentration and day of the test:

conc.  time (d)
(mg/L) 0   2   5   7   9   12  14  16  19  21
  0    10  10  10  10  10  10  10  10  10  10
  1    10  10  10  10  10  10  10  10  10  10
  5    10  10  10  10  10  10  10  10  10  10
 10    10  10  10  10  10  10  10  10  10  10

- Oxygen content (mg/L) ot the test solutions at the start of the test or  in the 2- or3-days old test solution:

conc.  range of oxygen between
(mg/L) day 0 and 21 (mg/L)
  0    8.2 - 15.5
  1    8.0 - 11.2
  5    7.9 - 11.9
 10    8.0 - 12.3

- pH of the test solutions at the start of the test or in the 2- or  3-days old test solution:

conc.  range of pH between
(mg/L) day 0 and 21 
  0    7.6 - 8.0
  1    7.6 - 8.1
  5    7.7 - 8.1
 10    7.5 - 8.2

Conclusions:

A chronic invertebrate toxicity test was conducted with the cladoceran D.magna, using sodium dithionite as test compound. A NOEC of >10 mg test item/L was derived and this data point can be used for hazard/effects asessment purposes for sodium dithionite and other dithionite compounds (read-across principles)

Description of key information

An effect of sodium dithionite on the reproduction and mortality of Daphnia magna was not observed in a 21-d chronic reproduction test (21 d NOEC ≥ 10 mg/L), indicating that sodium dithionite and other dithionite substances are not chronically toxic to freshwater invertebrates.

Furthermore, an effect of disodium disulfite on the reproduction and mortality of Daphnia magna was not observed in a 21-d chronic reproduction test (21 d NOEC ≥ 8.41 mg SO32-/L), indicating that sulfite/disulfite/thiosulfate substances are not chronically toxic to freshwater invertebrates. Furthermore, sodium as essential element has a very low potential for toxicity to aquatic invertebrates.

Based on data available for sodium dithionite and read-across to thiosulfate/sulfite/disulfite substances and soluble sodium substances and taking into account ubiquitousness and essentiality of sodium and sulfur, the potential of sodium dithionite for chronic toxicity to aquatic invertebrates is expected to be low.

Additional information

One study on the long-term toxicity of sodium dithionite to aquatic invertebrates is available (Daphnia magna, BASF 1994). In addition, read-across to thiosulfate and sulfite/disulfite substances is applied. Upon contact with water, salts of sulfur oxyacids including sodium dithionite dissociate into sulfur oxyacid anions and the respective counterions. Only the properties of the dithionite anion are considered a relevant determinant of environmental toxicity since sodium cations are essential and have a very low potential for acute toxicity to freshwater and marine invertebrates. Please refer to the respective endpoint summary for sodium (Na) for further details. Dithionite anions are unstable under environmentally relevant conditions and will rapidly disproportionate to (bi-)sulfites and thiosulfates (S₂O₃^2-) in aqueous media.Sulfites and thiosulfates are unstable in the environment, subject to transformation processes including oxidation to sulfate or reduction to sulfide, and will ultimately become part of the natural sulfur cycle.

 

Dithionite, thiosulfate and sulfite/disulfite substances –Long-term toxicity to aquatic invertebrates

In a reliable study (BASF, 1994) on the chronic toxicity of sodium dithionite (Na2S2O4) to the cladoceran Daphnia magna, an unbounded 21 d-NOEC ≥ 10 mg/L was derived for reproduction and mortality. Physico-chemical properties of the test media were monitored during the test, and pH (7.5-8.0) and oxygen content (>7 mg/L) met respective validity criteria.

In a reliable study (BASF, 1993) on the chronic toxicity of disodium disulfite (Na2S2O5) to the cladoceran Daphnia magna, an unbounded 21 d-NOEC ≥ 10 mg/L was derived for reproduction and mortality, corresponding to ≥ 8.41 mg SO32-/L. Physico-chemical properties of the test media were monitored during the test, and pH (7.5-8.0) and oxygen content (>7 mg/L) met respective validity criteria.