Tin difluoride

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: measured concentrations not reported; precipitation of tin salts occured --> Exposure concentration unclear; constitution of controls not described; pH values not in the recommended range; loading rate not assessable; number of replicates unknown

Qualifier:

according to guideline

Guideline:

EU Method C.1 (Acute Toxicity for Fish)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Vehicle:

no

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

the fish in the test ranged in weight from 0.71 to 2.56 g with a mean lenght of 44.3 mm

Test type:

semi-static

Water media type:

freshwater

Total exposure duration:

96 h

Hardness:

in the range 48.3-52.3 mg/l CaCO3

Test temperature:

15 +/- 1 °C

pH:

ranged from 5.4 to 7.8

Dissolved oxygen:

ranged from 9.2 to 9.8 mg/l

Salinity:

alkalinity ranged from 28.9 to 30.5 mg/l CaCO3

Conductivity:

conductivity of the water ranged from 130 to 140 microsiemens/cm

Reference substance (positive control):

no

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 38.4 other: mg Sn/L

Nominal / measured:

nominal

Conc. based on:

element

Basis for effect:

mortality (fish)

Details on results:

Observation of dead fish were recorded at 24, 48, 72 and 96 hr during the test, and at the same time a record of any symptoms of toxicity in the surviving fish was made. No fish deaths or symtoms of toxicity were observed in this study.
The 24, 48, 72, and 96 h LC50 were determined as greater than 100 mg/l based on nominal concentration

Validity criteria fulfilled:

yes

Conclusions:

No effect of tin (Sn) in the form of tin(II)methanesulfonate on the mortality of Oncorhynchus mykiss (length (mean): 44.3 mm; weight: 0.71-2.56 g) was observed at the tested concentrations in this semi-static test according to EU Method C.1. Thus, a 96 h LC50 of > 38.4 mg Sn/L (total Sn, nominal) was derived.

Executive summary:

It was not possible to expose fish to the test material. Exposure was only to the hydrolysis products.

Reference 2

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: no GLP compliance; application not verified; Sn dissolved at 1000 mg SnMSA/L (nominal) around 0.03 mg Sn/L; validity not assessable, oxygen content not measured; loading rate not assessable

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

Deviations:

yes

Remarks:

In contrast to the guidelines during the range finding test, individual batches of 5 fishes were exposed for a period of 96 h to a range of different concentrations of test sample under identical environmental standard conditions

GLP compliance:

no

Analytical monitoring:

yes

Details on sampling:

Samples were taken from the treatment with the highest concentration (1000 mg SnMSA/L).

Vehicle:

no

Test organisms (species):

Danio rerio (previous name: Brachydanio rerio)

Details on test organisms:

TEST ORGANISM
- Common name: Zebrafish
- Source: West Aquarium GmbH & Co. KG, Bad Lauterberg, Germany
- Age at study initiation: ca. 4 month
- Length at study initiation: 3.0 ± 0.5 cm

ACCLIMATION
- Acclimation period: 4 d
- Acclimation conditions (same as test or not): same as test (reconstituted water, recirculated and filtered continously)
- Type and amount of food during acclimation: TetraMin Hauptfutter; amount according to actual consumption observed
- Feeding frequency during acclimation: Twice daily
- Health during acclimation: No mortality observed

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Test temperature:

18.8 - 20.0 °C

pH:

7.17 - 7.64

Dissolved oxygen:

not less than 60% of the air saturation value, but no measurements reported

Nominal and measured concentrations:

Nominal: 0 (control), 10, 100, 1000 mg SnMSA/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Glass tanks
- Type: covered with glass plates
- Size, fill volume: length 300 mm, wifth 200 mm & height 220 mm; 10 L
- Aeration: continuous

- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1
- Biomass loading rate: not assessable

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: reconstituted water prepared acc. to OECD 203
- Alkalinity: 0.8 mmol/L
- Ca/mg ratio: 4:1


OTHER TEST CONDITIONS
- Photoperiod: not specified
- Light intensity: not specified

EFFECT PARAMETERS MEASURED:
- Mortality; at 1, 19, 43, 68 and 93 h

TEST CONCENTRATIONS
- Spacing factor for test concentrations: > 2.2
- Justification for using less concentrations than requested by guideline: not given

Reference substance (positive control):

no

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 384.3 other: mg Sn/L

Nominal / measured:

nominal

Conc. based on:

element (total fraction)

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 0.03 other: mg Sn/L

Nominal / measured:

meas. (not specified)

Conc. based on:

element (dissolved fraction)

Basis for effect:

mortality (fish)

Details on results:

All fish survived and no other relevant toxicological effects which were adverse for Zebra-fish were found under the condition of the test. Formation of precipitate was observed when solving the test substance in synthetic water. The test substance decomposed rapidly in water and formed water-insoluble tin salts.

Validity criteria fulfilled:

yes

Conclusions:

No mortality of Danio rerio (lenght: 3.0 ± 0.5 cm) exposed to tin (Sn) in the form of tin(II)methanesulfonate was observed after 96 h in this acute toxicity test conducted in reconstituted water according to OECD test guideline 203. A nominal LC50 (96 h) of > 384.3 mg Sn/L can be derived. Owing to the inherent chemical properties of the test substance (it decomposed in synthetic water and a precipitate was formed), measured values of dissolved tin varied greatly from nominal values and a 96 h LC50 of > 0.03 mg dissolved Sn/L (measured) was determined.

Executive summary:

Exposure was only to the hydrolysis products.

Reference 3

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: GLP compliance according to OECD 215 and EC method C14; acceptability of filters for tin analysis not checked; dissolved tin concentrations below 80% of nominal value

Qualifier:

according to guideline

Guideline:

other: OECD Guideline 215 (Fish, Juvenile Growth Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: EU Method C.14 (Fish Juvenile Growth Test)

Deviations:

no

Principles of method if other than guideline:

In a preliminary range finding test, the acute toxicity of SnMSA to juvenile Oncorhynchus mykiss was assessed at 96 h.

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

At test start and thereafter twice weekly, water was sampled at all test concentrations and analysed representatively for the content of methanesulfonate, dissolved tin and total tin content. Samples were taken from the test chambers at medium depth of the water column using a Pasteur pipette by pipetting sub-samples into 20 mL polyethylene vials.

Vehicle:

no

Details on test solutions:

A stock solution of 31.25 mg test item/L was prepared by mixing or agitating the test substance in the dilution water by using mechanical meands. The stock solution was continually dispensed and diluted with dilution water using the respective equipment to deliver a series of concentrations to the test chambers.

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM
- Common name: Rainbow trout
- Strain: Walbaum
- Source: freshly fertilized eggs were obtained from the NRW Landesanstalz für Fischerei (governmental fisheries agency), Germany
- Length at study initiation (mean and range, SD): 4.7-5.8 cm
- Weight at study initiation (mean and range, SD): 1.2-1.9 g
- Holding: Rainbow trout fingerling were reared at 14 ± 2 °C under flow-through conditionsin water of the same quality as used in the test. Trout were fed a ratio of 2 % body weight per day with commercial food (Trouvit Alleinfuttermittel, Milkivit, Germany)

FEEDING DURING TEST
- Food type: Trouvit 40/2 (Milkivit, Burgheim, Germany)
- Amount: 4 % of body weight
- Frequency: Twice daily

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Hardness:

1.0 mmol

Test temperature:

14 - 15 °C

pH:

7.7 - 8.3

Dissolved oxygen:

oxygen saturation between 76% and 96%

Conductivity:

179-181 µS/cm

Nominal and measured concentrations:

Nominal concentrations: 0 (control), 6.25, 12.5, 25.0, 50, 100 mg test item/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Full glass aquaria
- Material, size, headspace, fill volume: 42x28x28 cm (l x w x h); 25 L test solution
- Aeration: not specified
- Type of flow-through: Dilution water was pumped by a water dosage pump (membrane pump, prominent); stock solution was dispensed by a stock solution dosage pump (peristaltic pump)
- Renewal rate of test solution (flow rate): 5.2 L/h
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1
- Biomass loading rate: 0.62 g/L at test start

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Purified drinking water, filtrated with activated charcoal, passage through a lime-stone column and aeration untily oxygen saturation
- Dissolved organic carbon: 0.0 mg/L
- Alkalinity: 1.4-1.5 mmol
- Intervals of water quality measurement: Monthly

OTHER TEST CONDITIONS
- Photoperiod: light/dark 16/8 h
- Light intensity: 713-871 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Mortality; daily

Reference substance (positive control):

no

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 38.43 other: mg Sn/L

Nominal / measured:

nominal

Conc. based on:

element

Basis for effect:

mortality (fish)

Details on results:

No mortality was observed. Precipitation of the test item occurred in the aqueous solution.

Reported statistics and error estimates:

Survival data were analysed by means of probit analysis.

Validity criteria fulfilled:

yes

Conclusions:

No acute effect of Sn in the form of tin(II)methanesulfonate on the mortality of juvenile Oncorhynchus mykiss could be observed after 96 h of exposure in a preliminary flow-throught test conducted in purified drinking water, following OECD guideline 215, and an unbounded 96 h LC50 of > 38.43 mg Sn/L was derived.

Description of key information

Tin (Sn) is not acutely toxic to freshwater fish up to concentrations of 384.3 mg Sn/L (96 h LC50, nominal).

Additional information

Two acute freshwater fish toxicity studies (both RL3), in which test validities are either not assessable (Rabel et al. 1987) and/or the application of the test substances was not verified via chemical analysis (Rabel et al. 1987 and Hill et al. 1988) show comparable results. Therefore, they are evaluated in a weight of evidence approach to conclude on the acute toxic potential of tin (Sn). In both studies, test organisms were exposed to Sn in the form of tin(II)methanesulfonate. In a worst-case approach, all observed toxicity is attributed to Sn:

No effect of tin (Sn) in the form of tin(II)methanesulfonate on the mortality of Oncorhynchus mykiss (length (mean): 44.3 mm; weight: 0.71-2.56 g) was observed at the tested concentrations in this semi-static test according to EU Method C.1. Thus, an unbounded 96 h LC50 of > 38.4 mg Sn/L (total Sn, nominal) was derived (Hill et al. 1988).

No mortality of Danio rerio (length: 3.0 ± 0.5 cm) exposed to tin (Sn) in the form of tin(II)methanesulfonate was observed after 96 h in an acute toxicity test conducted in reconstituted water according to OECD test guideline 203. A nominal LC50 (96 h) of > 384.3 mg Sn/L can be derived. Owing to the inherent chemical properties of the test substance (it decomposed in synthetic water and a precipitate was formed), measured values of dissolved tin varied greatly from nominal values and a 96 h LC50 of > 0.03 mg dissolved Sn/L (measured) was determined (Rabel et al. 1987).

That Sn is not acutely toxic to freshwater fish is confirmed by a reliable (RL2), supporting study of Schäfers et al. (2006): Juveniles of Oncorhynchus mykiss were exposed to Sn in the form of tin(II)methanesulfonate in a preliminary flow-through acute toxicity test to determine the exposure concentration range to be used in the GLP conform full chronic freshwater fish test with tin(II)methanesulfonate according to OECD guideline 215. No mortality of juvenile Oncorhynchus mykiss could be observed after 96 h of exposure, and an unbounded 96 h LC50 of > 38.43 mg Sn/L (nominal) was derived. Furthermore, in the full GLP conform chronic toxicity test, in which lower tin(II)methanesulfonate concentrations were tested, no mortality was observed up to 1.22 mg Sn/L (nominal) after 8 d of exposure and an unbounded 8 d LC50 of > 1.22 mg Sn/L (nominal) was derived.

Data on marine organisms is not available.

Finally, it is concluded that Sn is not acutely toxic to freshwater fish up to nominal concentrations of 384.3 mg Sn/L (96 h LC50, nominal).

Read across justification:

Tin difluoride is an inorganic solid at room temperature and consists of the tin cation and fluoride anions. Based on the solubility of tin difluoride in water (300-428 g/L according to handbook data (Merck, 2006; Gestis, 2015)), a complete dissociation of tin difluoride resulting in tin and fluoride ions may be assumed under environmental conditions. The respective dissociation is reversible and the ratio of the salt /dissociated ions is dependent on the metal-ligand dissociation constant of the salt, the composition of the solution and its pH. The metal-ligand equilibrium constant for the formation of tin difluoride is reported as follows (Japan Nuclear Cycle Development Institute, 1999):

Sn²⁺+ 2F^-↔SnF2⁰(log K =7.74)

Thus, it may reasonably be assumed that based on the tin-difluoride formation constant, the respective behaviour of the dissociated tin cations and fluoride anions in the environment determine the fate of tin difluoride upon dissolution with regard to (bio)degradation, bioaccumulation, partitioning resulting in a different relative distribution in environmental compartments (water, air, sediment and soil) and subsequently determine its ecotoxicological potential.

Therefore, in the assessment of the ecotoxicity of tin difluoride, read-across to data for fluoride and soluble tin substances is applied since only the ions of tin difluoride are available in an aqueous environment and determine the environmental fate and toxicity. Read-across to environmental fate and toxicity studies of soluble tin salts, including tin dichloride and tin methane sulfonic acid, is therefore appropriate and scientifically justified.