Sodium dithionite

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-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:

1989-05-08 to 0989-05-10

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Comparable to guideline study with acceptable restrictions (eg. low initial oxygen concentration at higher test concentrations - inherent property of the test substance when brought in aqueous solution)

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:

Directive 79/831/EEC, Annex V, Part C

GLP compliance:

no

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: 500 mg/l nominal.
- Differential loading: 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

Test type:

static

Water media type:

freshwater

Total exposure duration:

48 h

Hardness:

2.7 ± 0.5 mmol/l total hardness

Test temperature:

20-22 °C

pH:

see below

Dissolved oxygen:

see below

Nominal and measured concentrations:

- Test concentrations: 0.976, 1.95, 3.9, 7.81, 15.6, 31.2, 62.5, 125.0, 250.0, 500.0 mg/L (nominal)

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Type (delete if not applicable): no data
- Material, size, headspace, fill volume: 20 ml glass tubes with flat bottom, 10 ml test volume
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: reconstituted water using deionized water was prepared and then aerated (oil-free air) and stored for 24h hours to allow stabilization.
Total hardness: 2.88 mmol/L
Alkalinity up to pH 4.3: 0.97 mmol/L
Ratio Ca/Mg ions: about 4:1
pH value: 8.0
Conductivity: 690 microS/cm


OTHER TEST CONDITIONS
- Photoperiod: 16:8 hours, diffuse light (about 5 microeinstein/m*m*s (400-750 nm))


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
Observations: mobile daphnids after 0, 3, 6, 24 and 48 h
Measurements: Temperature, pH and oxygen content after 0 and 48 h


TEST CONCENTRATIONS
Nominal test concentrations: 0.976, 1.95, 3.9, 7.81, 15.6, 31.2, 62.5, 125.0, 250.0, 500.0 mg/L (nominal). A control was tested in parallel.

Duration:

48 h

Dose descriptor:

EC0

Effect conc.:

62.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC100

Effect conc.:

250 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

98.31 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 59.61-162.12

Details on results:

- Mortality of control: no

- Number of mobile test animals after exposure (48 h) to
various test concentrations:
concentration (mg/L)  mobile daphnids
      0.976                 20
      1.95                  20
      3.9                   20
      7.81                  20
     15.6                   20
     31.2                   20
     62.5                   19
    125.0                    4
    250.0                    0 
    500.0                    0 
   control                  20    

- Effect values after 48 h:
  EC50 = 98.31 mg/L 
   95 % confidence limits: 59.61 - 162.12 mg/L

- Effect values after 24 h:
  EC0   = 62.5 mg/L
  EC50  = 116.88 mg/L
   95 % confidence limits: 79.64 - 171.54 mg/L
  EC100 = 250.0 mg/L

- pH at start:  concentration (mg/L)    pH
                     0.976             7.97
                     1.95              7.93
                     3.9               7.88
                     7.81              7.77
                    15.6               7.62
                    31.2               7.33
                    62.5               7.02
                   125.0               6.61
                   250.0               5.97 
                   500.0               5.58 
                  control              8.01    

- pH after 48 h: concentration (mg/L)   pH
                     0.976             7.99
                     1.95              7.99
                     3.9               7.99
                     7.81              7.99
                    15.6               7.97
                    31.2               7.94
                    62.5               7.85
                   125.0               7.27
                   250.0               5.29 
                   500.0               3.65 
                  control              8.01    

- Oxygen (O2, mg/L) at start:
                concentration (mg/L)   oxygen
                     0.976             9.40
                     1.95              9.33
                     3.9               9.18
                     7.81              9.04
                    15.6               8.86
                    31.2               8.43
                    62.5               7.42
                   125.0               5.10
                   250.0               0.56 
                   500.0               0.40 
                  control              9.22   
 
- Oxygen (O2, mg/L) after 48 h: 
                concentration (mg/L)   oxygen
                     0.976             8.51
                     1.95              8.42
                     3.9               8.32
                     7.81              8.28
                    15.6               8.23
                    31.2               8.21
                    62.5               7.96
                   125.0               7.66
                   250.0               8.05 
                   500.0               1.44 
                  control              8.33

- Mortality at 250.0 mg/L and 500.0 mg/L may be due to
oxygen deficiency in the test assays

Conclusions:

A standard acute invertebrate toxicity test was conducted with the cladoceran D.magna, using sodium dithionite as test compound. An LC50 of 98.3 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)

Reference 2

Endpoint:

short-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:

1989-05-08 to 1989-05-10

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study with acceptable restrictions; dissolved oxygen <3 mg/L at higher test concentrations; 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:

according to guideline

Guideline:

other: 79/831/EEC, appendix V, part C

GLP compliance:

no

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: A stock solution was prepared (500 mg/l). Following this, serial dilutions of this test medium were prepared in order to obtain the desired test concentrations.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Source: originally obtained from the Institute National de Recherche Chimique Appliquee, France and cultured in the laboratories of BASF since 1978.
- Age at study initiation (mean and range, SD): 2 - 24 h
- Age of stock animals: 2-4 weeks

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

2.88 mmol/

Test temperature:

20±1°C

pH:

test start: 8.05 - 5.39 mg/l
test end: 8.11 - 4.05 mg/l

Dissolved oxygen:

test start: 9.53 - 0.35 mg/l (see also below)
test end: 8.17 - 5.54 mg/l

Nominal and measured concentrations:

0, 7.813, 15.6, 31.3, 62.5, 125.0, 250.0, 500,0 mg/l (nominal)

Details on test conditions:

TEST SYSTEM
- Test vessel: Flat bottom glass tubes
- Fill volume: 10 ml
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: De-chlorinated tap water
- Ca/mg ratio: 4:1
- Conductivity: 600-700 µSiemens/cm

OTHER TEST CONDITIONS
- Light intensity: diffuse light


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
Mobility after 0, 3, 6, 24 and 48 h

Duration:

48 h

Dose descriptor:

EC0

Effect conc.:

62.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC100

Effect conc.:

125 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

89 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Conc. (mg/L)	Dissolved oxygen after 0h (mg/)	Dissolved oxygen after 48h (mg/L)
7.813	9.53	7.47
15.6	9.12	7.73
31.3	7.76	8.03
62.5	3.09	8.13
125	0.74	8.08
250	0.49	7.73
500	0.35	5.54
0	9.47	8.17

Dissolved oxygen (DO) concentrations decreased with increasing substance concentrations at test start, ranging from 9.53 mg/l DO at 7.8 mg/l substance concentration to 0.35 mg/l DO at 500 mg/l. However, at test end DO concentrations were considerably higher ranging from 5.54 to 8.17 for all concentrations tested. Therefore, mortality at concentrations of 125 - 500 mg/l might be explained by high oxygen consumption at start of the test.

EC0, EC50 and EC100 -values are given in nominal concentration.
results after 24 h:
EC0   = 62.5 mg/l
EC50  = 88.8 mg/l
EC100 = 125  mg/l 

Validity criteria fulfilled:

not applicable

Remarks:

no control immobilization; dissolved oxygen <3 mg/L at higher test concentrations

Conclusions:

A standard acute invertebrate toxicity test was conducted with the cladoceran D.magna, using sodium disulfite (Na2S2O5) as test compound. A 48 h EC50 of 89 mg test item/L (nominal) was derived, which corresponds to 74.9 mg sulfite/L (nominal). However, at concentrations of 125 mg test item/L and higher, the dissolved oxygen concentration in the test vessels dropped below the acceptable limit of 3.0 mg/L as specified in OECD test guideline 202. Since dissolved oxygen concentrations were at 3.09 mg/L in the 62.5 mg/L treatment, it can be assumed that they were below the acceptable range (<3 mg/L) at concentrations above, which includes the EC50 value of 89 mg test item/L. Effects observed on the mobility of D. magna at this level are thus presumably associated with indirect effects of oxygen depletion.

Reference 3

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

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

Adequacy of study:

weight of evidence

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline followed. Methodology well destribed.

Justification for type of information:

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

Qualifier:

according to guideline

Guideline:

other: Bionomics protocol for static acute toxicity with th water flea (Daphnia magna), December 1983

Principles of method if other than guideline:

Similar to OECD guidance

GLP compliance:

no

Analytical monitoring:

no

Details on test solutions:

A clear colorless stock solution of 100 mg/L was prepared by adding 2.5 grams of ammonium thiosulfate to a 25 mg/L columetric flask, which was then filled to volume with distilled water. The test solutions were prepared by adding the appropiate volume of stock solution to dilution water to total 1000mL.

Test organisms (species):

Daphnia magna

Details on test organisms:

The daphnids used in this toxicity test were obtained from laboratory cultures maintained at Springborn Bionomics, Inc., Wareham, Massauchusetts.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

Total hardness: 150 mg/L as CaCO3

Test temperature:

20 +- 1 °C

pH:

7.3-7.9

Dissolved oxygen:

greater than 60% of saturation

Nominal and measured concentrations:

1000, 600, 360, 220 and 130 mg/L

Details on test conditions:

250 mL glass beakers

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

230 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

360 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Reported statistics and error estimates:

probit analysis

Conclusions:

A standard acute invertebrate toxicity test was conducted with the cladoceran D.magna, using ammonium thiosulfate as test compound. A 48h EC50 of 230 mg test item/L was derived and this data point can be used for hazard/effects asessment purposes for ammoniu mthiosulfate and other thiosulfate compounds (read-across principles)

Reference 4

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

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

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study with acceptable restrictions

Justification for type of information:

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

Guideline:

other: FIFRA Guideline 72-3, SLI protocol #:120992/FIFRA 72-3 MYS-SA (Appendix 1)

Guideline:

other: Standard Evaluation Procedure issued by the Hazard Evaluation Division of EPA's Office of Pesticides Program (U.S. EPA, 1982)

Principles of method if other than guideline:

Routine water and food contaminant screening analyses for pesticide, PCB's and toxic metals were conducted using standard US EPA procedures by Lancaster Laboratories, Pennsylvania, USA. These data were not collected in accordance with GLP procedures. Stability, characterization, and verificiation of the test material identity and maintenance of records on the test material are the responsibilty of the Study Sponsor.

Analytical monitoring:

no

Details on test solutions:

Prior to test initation, a 25 mg A.I./mL stock solution was prepared by dissolving ammonium thiosulfate with distilled water to volume in a 200mL volcumetric flask.Treatment level solutions were prepared by adding the appropriate amount of 25 mg A.I./mL stock solution directly to 1.0L of dilution water which resulted in the desired test concentration.

Test organisms (species):

Americamysis bahia (previous name: Mysidopsis bahia)

Details on test organisms:

source: the mysid shrimp used in this study were obtained from laboratory cultures maintained at SLI and held in a 500-L fiberglass tank under a photoperiod of 16 hours light and 8 hours darkness.

Test type:

static

Water media type:

saltwater

Limit test:

no

Total exposure duration:

96 h

Hardness:

Seawater

Test temperature:

25+-1 °C

pH:

7.2-7.8

Dissolved oxygen:

Measured during tests, no aeration.

Salinity:

25-26 °/oo

Nominal and measured concentrations:

0, 30, 48, 78, 130, 220, 350, 600, 1000 mg/L (nominal)

Details on test conditions:

The toxicity test was conducted in 1.6L glass vessels which contained 1.0L of test solution. The test solution in each aquarium had a depth of 3.5 cm with a surface area of 280 cm2.

Duration:

24 h

Dose descriptor:

LC50

Effect conc.:

190 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: (lower and upper 95% confidence interval = 140 and 270)

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

80 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: (lower and upper 95% confidence interval = 64 and 100)

Duration:

72 h

Dose descriptor:

LC50

Effect conc.:

77 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: (lower and upper 95% confidence interval = 62 and 97)

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

77 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: (lower and upper 95% confidence interval = 62 and 97)

Reported statistics and error estimates:

probit analysis

Table: Dissolved oxygen concentrations and % saturation over the 96 h test

Test item concentration [mg/L]	Dissolved oxygen (mg/L) (% saturation)
	0 h	24 h	48 h	72 h	96 h
0	7.7 (105)	6.4 (88)	6.2 (85)	5.9 (81)	6.4 (88)
30	7.6 (104)	5.8 (79)	5.5 (75)	5.7 (78)	6.1 (84)
48	7.6 (104)	5.6 (77)	4.5 (62)	4.3 (59)	6.2 (85)
78	7.6 (104)	5.6 (77)	3.3 (45)	3.0 (41)	6.1 (84)
130	7.6 (104)	5.8 (79)	3.0 (41)	-	-
220	7.6 (104)	5.9 (81)	2.9 (40)	-	-
350	7.6 (104)	5.8 (79)	2.7 (37)	-	-
600	7.6 (104)	5.9 (81)	-	-	-
1000	7.6 (104)	6.1 (84)	-	-	-

Conclusions:

An acute toxicity test was conducted with the mysid shrimp M.bahia (new name: A.bahia), using ammonium thiosulfate as test compound, and a 96 h LC50 of 77 mg test item/L was derived. However, at concentrations of 48 mg test item/L and higher, the dissolved oxygen concentration in the test vessels dropped below the acceptable limit of 60 % saturation as specified in “Ecological Effects Test Guidelines OCSPP 850.1035: Mysid Acute Toxicity Test”. Since dissolved oxygen concentrations were down to 41 % of air saturation and thus significantly below 60 % saturation at the test concentration of 78 mg test item/L, which is close to the derived LC50 of 77 mg/L, effects observed on the mortality of M. bahia at this level are presumably associated with indirect effects of oxygen depletion.

Description of key information

A 48 h EC50 of 98.3 mg sodium dithionite/L was determined in a reliable short-term toxicity test with Daphnia magna. Since the derived EC50 is close to the acute OECD test limit of 100 mg/L and significant effects were only observed at concentrations above this limit, i.e. at 125 mg test item/L, the potential of sodium dithionite for acute toxicity to aquatic invertebrates is considered to be low. Furthermore, thiosulfate and sulfite/disulfite substances are not acutely toxic to freshwater and marine invertebrates up to the limit concentration of 100 mg/L (EC50 > 100 mg/L). In addition, sodium as essential element has a very low potential for acute toxicity to freshwater and marine 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 acute toxicity to aquatic invertebrates is expected to be low. A confirmatory study on the acute effects of disodium disulfite to Daphnia magna according to OECD 202 with appropriate aeration and buffering of the test system is currently ongoing.

Additional information

One study on the short-term toxicity of sodium dithionite to aquatic invertebrates is available (Daphnia magna, BASF 1989). In addition, read-across to thiosulfate and sulfite/disulfite and soluble sodium 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 –Short-term toxicity to aquatic invertebrates

A 48 h LC50 of 98.3 mg Na2S2O4/L was derived for sodium dithionite in a standard acute invertebrate toxicity test conducted with Daphnia magna.

 

In a reliable study on the immobilisation of freshwater invertebrate Daphnia magna by ammonium thiosulfate, a 48-h EC50 of 230 mg/L was derived, corresponding to 124.2 mg SO32-/L.

 

Further, in a study on the acute toxicity of disodium disulfite (Na2S2O5) to Daphnia magna, the 48h-EC50 is reported with 89 mg/L, corresponding to 74.9 mg SO32-/L (BASF, 1990). However, observed effects are presumably related to oxygen depletion resulting from sulfite oxidation. At concentrations of ≥ 125 mg/L, dissolved oxygen concentration dropped below the acceptable limit of 3.0 mg/L as specified in OECD TG 202. Since dissolved oxygen concentrations were at 3.09 mg/L at 62.5 mg/L, it is assumed that concentrations were below the acceptable range (< 3 mg/L) at concentrations > 62.5 mg/L and at the EC50 of 89 mg/L. It can thus not be excluded that effects observed on the mobility of D. magna at this level are associated with indirect effects of oxygen depletion.

 

In a supporting study by Dowden and Bennett (1965), acute effects of sodium sulfite on Daphnia magna were studied in a non-guideline test and a 50-h TLm50 (median tolerance limit) of 273 mg/L, corresponding to 173.2 mg SO32-/L, was determined. It should be noted that the reported parameter 50-h TLm50 is not a standard endpoint.

 

Regarding toxicity in saltwater, one study with ammonium thiosulfate is available for Americamysis bahia (formerly Mysidopsis bahia), which reports a 96-h LC50 of 77 mg/L, corresponding to 41.6 mg SO32-/L. However, at concentrations ≥ 48 mg/L, the dissolved oxygen concentration dropped below the acceptable limit of 60 % saturation as specified in “Ecological Effects Test Guidelines OCSPP 850.1035: Mysid Acute Toxicity Test”. Since dissolved oxygen concentrations were down to 41 % of air saturation and thus significantly below 60 % saturation at 78 mg/L, a concentration close to the derived LC50 of 77 mg/L, effects observed on the mortality of A. bahia at this level are presumably associated with indirect effects of oxygen depletion.

 

In sum, in the absence of oxygen depletion, acute toxicity is only observed at a concentration around or well above the respective OECD test limit of 100 mg/L, i.e., at 230 mg ammonium thiosulfate (corresponding to 124.2 mg sulfite/L).The TLm derived for sodium sulfite in the supporting study by Dowden and Bennett (1965) is also above the test limit. However, information on pH and oxygen levels during the test are not available and it is thus not possible to confirm stable conditions. Since effects observed < 100 mg/L are presumably caused by oxygen depletion and do not represent the intrinsic toxicity of dithionite/thiosulfate/sulfite/disulfite substances, it is concluded that dithionite/thiosulfate/sulfite/disulfite substances are not acutely toxic to freshwater and marine invertebrates. Nevertheless, a confirmatory study on the acute effects of disodium disulfite to Daphnia magna according to OECD 202 with appropriate aeration and buffering of the test system is currently ongoing.