Tin difluoride

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:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: Exposure concentration not chemically verified, validity not assessable, test did not exacty follow existing guidance (1972-study), but test method well described and test conditions (eg.g. test medium composition) were properly identified.

Qualifier:

no guideline available

Principles of method if other than guideline:

Not a guideline study but meets generally accepted scientific standards and methodology is well documented and described

GLP compliance:

not specified

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Daphnia magna
- Strain: laboratory clone
- Source: University of Michigan
- Age at study initiation (mean and range, SD): 12h +/- 12h
- Feeding during test: no

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

45.2 mg/L as CaCO3

Test temperature:

18 +/- 1 °C

pH:

7.74

Dissolved oxygen:

+/- 9 mg O2/L

Salinity:

not reported

Nominal and measured concentrations:

nominal/measured test concentrations not reported: geometric series of 5-12 concentrations (not specified for Sr)

Details on test conditions:

- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates):2
- No. of vessels per control (replicates): not reported



TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Lake Superior water; unfiltered water strained through a #20 bolting cloth
- Metals: 14 µg Ba/L ; 16 µg Sr/L ; 0.78 µg Zn/L ; <0.5 µg Ni/L ; 1.51 µg Cu/L ; <0.5 µg Co/L ; < 0.01 g Hg/L ; < 0.1 µg Cd/L
- Chloride: 1.22 mg/L
- Alkalinity: 42.3 mg/L as CaCO3
- Ca: 13.7 mg /L
- Mg: 3.12 mg/L
- K: 0.53 mg/L
- Na: 1.13 mg/L


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : complete immobilisation or death

Reference substance (positive control):

no

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

55 000 µg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

metal ion -based

Basis for effect:

mortality

Remarks:

including immobility

Remarks on result:

other: not reported

Reported statistics and error estimates:

Results were statistically evaluated with the method of Litchfield and Wilcoxon (1949). LC50 was used for survival and represents an interpolation from three or more partial-effect concentrations.

Chemical characteristics of Lake Superior water were monitored during the testing period according to procedures outlined by the American Public Health Association and procedures employing atomic absorption spectroscopy.

Validity criteria fulfilled:

no

Conclusions:

The effect of tin (Sn) in the form of tin chloride dihydrate (SnCl2 * 2 H2O) on the mobility of Daphnia magna (age: 12 ± 12 h) was assessed in this 48 h acute toxicity test conducted in Lake Superior water in a static test system, following no specific guideline. A 48 h LC50 of 55000 µg Sn/L (nominal) was derived, however exposure concentrations were not analytically verified.

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: No data are provided on test method, physicochemistry of ther test medium, or applied statistics. Exposure period of 64h is not relevant for hazard assessment purposes, validity not assessable

Qualifier:

no guideline followed

Principles of method if other than guideline:

Test methodology was poorly described.

GLP compliance:

not specified

Analytical monitoring:

not specified

Test organisms (species):

Daphnia magna

Details on test organisms:

no specific information was provided

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

64 h

Hardness:

not reported (Lake Erie water)

Test temperature:

not reported

pH:

not reported (Lake Erie water)

Dissolved oxygen:

not reported

Nominal and measured concentrations:

not reported

Duration:

64 h

Dose descriptor:

LC50

Effect conc.:

< 66 000 µg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

metal ion (derived from molar value)

Basis for effect:

mortality

Reported statistics and error estimates:

No statistics are reported

Validity criteria fulfilled:

not specified

Conclusions:

The acute effect of tin (Sn) in the form of tin(II) chloride on the mortality of Daphnia magna was assessed in a 64 h test conducted in Lake Eerie water, following no specific guideline. A 64 h LC50 value of 66 mg Sn/L (nominal) was reported. The reported effect concentration is however only considered supportive as no data on test method are provided, information on physisochemistry of the test medium is lacking, and statistics are not reported. Furthermore, the exposure period of 64 h is not relevant for hazard assessment purposes.

Reference 3

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: Study conducted in GLP accreditated laboratory according to EU Method C.2

Remarks:

no information on life stage of test organisms, controls, purity, feeding, test concentrations, chemical analytical method, loading rate, replicates; precipitation of tin salts reported and measured concentrations were < 20% of the nominal concentrations; measured concentrations not reported

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

Daphnia magna

Details on test organisms:

obtained from continuous laboratory cultures

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Test temperature:

the temperature recorded at 0, 24 and 48 hours were 20.1, 20.3 and 19.9 °C respectively

pH:

ranged from 7.72 to 8.48

Dissolved oxygen:

ranged from 8.3 to 9.2 mg/l

Reference substance (positive control):

no

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 38.43 other: mg Sn/L

Nominal / measured:

nominal

Conc. based on:

element

Basis for effect:

mobility

Validity criteria fulfilled:

yes

Conclusions:

A toxic effect of tin (Sn) in the form of tin(II)methanesulfonate on Daphnia magna (age not spcified) could be observed in this 48 h acute toxicity test, following EU method C.2. A 48 h EC50 of > 38.43 mg Sn/L (nominal) for the immobilisation of daphnids was determined. However, precipitation of tin salts occurred and measured concentrations were below 80 % of nominal values (measured values not reported).

Reference 4

Endpoint:

short-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 conducted in GLP accredited laboratory according to OECD 211 and EC method C.20 T

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

other: OECD Guideline 211 (Daphnia magna Reproduction Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: EU Method C. 20 (Daphnia magna Reproduction Test)

Principles of method if other than guideline:

The immobilisation of Daphnia magna was assessed after 7 d exposure to SnMSA in purified drinking water in a semi-static system.

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

At test start and afterwards three times weekly, a sample was taken for the analysis of methanesulfonate, dissolved tin and total tin content of each test concentration from the test solution preparation (fresh solution). At each removal, aged test solutions were analysed for dissolved tin and methanesulfonate.

Vehicle:

no

Details on test solutions:

Each test concentration was prepared by weighing adequate amounts of the test item into a mixing vessel, stirring it for 20 h and distributing it to replicates. The pH of diultion water was adjustet to pH 7.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Strain/clone: Daphnia magna Straus
- Source: Umweltbundesamt (German Federal Environment Agency), bred in the laboratory of the testing facillity
- Age of parental stock: at least 3 weeks old
- Age at study initiation: < 24 h
- Feeding during test
- Food type: Suspensions of unicellular green algae
- Amount: 7 mg C/L to 15 mg C/L
- Frequency: not specified

ACCLIMATION
- Acclimation period: not specified
- Acclimation conditions (same as test or not): at room temperature, in dilution water
- Type and amount of food: algal suspension (Scenedesmus subspicatus) and LiquizeIIR
- Feeding frequency: daily

METHOD FOR PREPARATION AND COLLECTION OF EARLY INSTARS OR OTHER LIFE STAGES:
- Newborn daphnia are separated by sieving, the first generation is discarded.

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

7 d

Hardness:

total hardness 1.0 mmol/L

Test temperature:

20 +/- 0.5 °C

pH:

from 7.7 to 7.9

Dissolved oxygen:

The oxygen saturation between 85% and 121%., never below 7.0 mg/L

Salinity:

Alkalinity 1.4-1.6 mmol/L;

Conductivity:

Conductivity 181-192 microS/cm

Nominal and measured concentrations:

The study was conducted at nominal concentration of 6.25, 12.5, 25, 50 and 100 mg test item/L.

Details on test conditions:

TEST SYSTEM
- Test vessel: 60 mL glass beakers
- Type: covered with a glass pane
- Fill volume: 50 mL
- Aeration: none
- Renewal rate of test solution (frequency): three times weekly
- No. of organisms per vessel: 1
- No. of vessels per concentration (replicates): 10
- No. of vessels per control (replicates): 10

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Purified drinking water (filtration with activated charcoal, passage through a lime-stone column & aeration until oxygen saturation)
- Dissolved organic carbon: 0 mg/L
- Conductivity: 181-192 µS/cm

OTHER TEST CONDITIONS
- Photoperiod: light/dark 16/8 h
- Light intensity: 700 ± 50 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- immobility

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2
- Range finding study
- Test concentrations: Up to 100 mg/L
- Results used to determine the conditions for the definitive study: No toxicity at 100 mg/L in a 48 h acute toxicity test.

Reference substance (positive control):

no

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

> 38.43 other: mg Sn/L

Nominal / measured:

nominal

Conc. based on:

element

Basis for effect:

mobility

Remarks on result:

other: Nominal concentrations analytically confirmed

Details on results:

Effect values are based on nominal concentrations, but are analytically verified (measured values of total tin and MSA > 80 % of nominal values).
No immobilisation of daphnids was observed up to 38.43 mg Sn/L (nominal total tin, chemically confirmed) after 7 d of exposure.

Reported statistics and error estimates:

ECx values (and 95 % CLs) were determined by regression using Probit-analysis, assuming log-normal distribution of values.

Results of analysis for fresh media (t = 0 hr) and aged (2 - 3 days) prior to media change for dissolved tin gave the following recoveries:

6.25 mg/l test substance = 37 % recovery of expected dissolved tin at t = 0 hr (mean 0.875 mg/l tin) and 0% aged (2 -3 days)

12.5 mg/l = 29% (mean 1.354 mg/l tin) and 0% aged samples

25.0 mg/l = 18% (mean 1.706 mg/l tin) and 5% (0.498 mg/l) aged

50.0 mg/l = 2.8% (mean 0.527 mg/l) and 2.8% (0.532 mg/l) aged

100 mg/l = 0 % (< limit of quatification) and 1.4% (0.530 mg/l) aged

It is clear from this work that a long term solubility of tin salts is about 0.5 mg/l and the fact that the nominal 50 and 100 mg/l concentrations cause immobilisation and no effect to vigour was seen at 25 mg/l or lower suggests that it is not the dissolved tin that is causing the immobilisation but probably exposure to the precipitate.

Validity criteria fulfilled:

yes

Conclusions:

In a GLP confirm chronic toxicity study with Daphnia magna (< 24 h) no immobilisation was observed after 7 d of exposure to Sn in the form of tin(II)methanesulfonate in purified drinking water in a semi-static test, conducted according to OECD guideline 211. An acute unbounded 7 d EC50 of > 38.34 mg Sn/L (nominal, total tin) was derived for the immobilisation of Daphnia magna. Nominal concentrations were chemically verified, with concentrations for total tin and methansulfonate > 80 % of nominal values (Schäfers et al. 2006).

Executive summary:

It is clear from this work that the solubility of tin salts is about 0.5 mg/l and the fact that the nominal 50 and 100 mg/l concentrations cause immobilisation and no effect to vigour was seen at 25 mg/l or lower suggests that it is not the dissolved tin that is causing the immobilisation but probably exposure to the precipitate.

Reference 5

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: no purity reported; only 1 instead of 4 replicates tested; acclimatisation status unclear; exposure concentrations not chemically verified

Qualifier:

according to guideline

Guideline:

other: DIN 38 412

Qualifier:

according to guideline

Guideline:

other: EG-Prüfrichtlinie 84/449

Version / remarks:

1984

GLP compliance:

no

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

The test material is dissolved in water.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Strain/clone: Daphnia magna Strauss
- Source: laboratory culture
- Age of at study initiation: < 24 h
- Feeding during test: no

ACCLIMATION
- Acclimation period: not specified
- Acclimation conditions (same as test or not): not specified
- Type of food: Chlorella vulgaris

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

total hardness: 19.1 °dH (3.41 mmol/L)

Test temperature:

20 ± 2 °C

pH:

7.7-7.9

Dissolved oxygen:

92-99 %

Nominal and measured concentrations:

Nominal concentrations: 0 (control), 50, 100, 200, 400, 600, 1200, 2200 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 250 ml beakers
- Fill volume: 40 ml
- No. of organisms per vessel: 20
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1
- Biomass loading rate: 20 daphnids/40 ml

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: test medium ISO DIN 38412 (Part 11)

OTHER TEST CONDITIONS
- Photoperiod:light/dark 1/8 h

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- immobilisation, at 24 and 48 h

Reference substance (positive control):

no

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

281.8 mg/L

Nominal / measured:

nominal

Conc. based on:

other: MSA

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC0

Effect conc.:

< 40.26 mg/L

Nominal / measured:

nominal

Conc. based on:

other: MSA

Basis for effect:

mobility

Details on results:

The test substance was water soluble (100g/100 ml water). Control mortality ≤ 10 %.

Reported statistics and error estimates:

Probit analysis and linear regression.

Validity criteria fulfilled:

yes

Conclusions:

The effect of sodium methanesulfonate on the mobility of Daphnia magna (age: < 24 h) was tested in a 48 h acute toxicity test following DIN standard 38412 (part 11). A 48 h EC50 of 281.8 mg MSA/L (nominal) and an EC0 of < 40.26 mg MSA/L (nominal) could be derived. The exposure concentrations were however not chemically verified and only 1 replicate was tested at each test concentration.

Description of key information

Sn is not acutely toxic to freshwater invertebrates up to concentrations of 38.43 mg Sn/L (unbounded 7 d EC50, nominal total tin, analytically confirmed). Above these concentrations, Sn shows a low acute toxic potential, as indicated by a 48 h EC50 value of 55 mg Sn/L (nominal) derived from supporting data.

Additional information

One key study of appropriate reliability and several supporting acute freshwater invertebrate studies for Sn, tested in the form of either tin(II)methanesulfonate or tin dichloride, are available.

Due to the low acute invertebrate toxicity of methanesulfonate (Dommröse et al. 1987, 48 h EC50 of 281.8 mg MSA/L (nominal)), it is expected that potential toxicity of tin(II)methanesulfonate on daphnids is not associated with methanesulfonate but with Sn. In a worst-case approach, all toxicity observed for SnCl2 is attributed to Sn:

 

In a reliable (RL1), GLP confirm chronic, freshwater toxicity study with Daphnia magna (< 24 h) no immobilisation was observed after 7 d of exposure to Sn in the form of tin(II)methanesulfonate in purified drinking water in a semi-static test, conducted according to OECD guideline 211. An acute unbounded 7 d EC50 of > 38.34 mg Sn/L (nominal, total tin, chemically verified) was derived for the immobilisation of Daphnia magna. Nominal concentrations were chemically verified, with concentrations for total tin and methansulfonate > 80 % of nominal values (Schäfers et al. 2006).

 

Further, this low acute freshwater toxicity potential of Sn is confirmed by several supporting (RL3) acute toxicity studies with Daphnia magna, showing 48 h EC50 values ranging from > 38.43 mg Sn/L (nominal) to 55.0 mg Sn/L (nominal) and a 64 h EC50 value of 66.0 mg Sn/L (nominal).

 

A toxic effect of tin (Sn) in the form of tin(II)methanesulfonate on Daphnia magna (age not specified) was observed in a 48 h acute toxicity test, following EU method C.2. An unbounded 48 h EC50 of > 38.43 mg Sn/L (nominal) for the immobilisation of daphnids was determined. However, precipitation of tin salts occurred and measured concentrations were below 80 % of nominal values (measured values not reported, Hill and Williams 1988). Results and methods are not well reported and test concentrations were not chemically verified. Hence this study is only considered supporting.

 

Biesinger & Christensen (1972) assessed the effect of tin (Sn) in the form of tin chloride dihydrate (SnCl2 * 2 H2O) on the mobility of Daphnia magna (age: 12 ± 12 h) in a 48 h acute toxicity test conducted in Lake Superior water in a static test system, following no specific guideline. A 48 h LC50 of 55.0 mg Sn/L (nominal) was derived. Since validity of the test was not assessable and exposure concentrations were not chemically confirmed, this study is only considered supporting.

 

The acute effect of tin (Sn) in the form of tin(II) chloride on the mortality of Daphnia magna was assessed in a 64 h test conducted in Lake Eerie water, following no specific guideline. A 64 h LC50 value of 66.0 mg Sn/L (nominal) was reported. The reported effect concentration is however only considered supportive as no data on test method are provided, information on physicochemistry of the test medium is lacking, and statistics are not reported. Furthermore, the exposure period of 64 h is not relevant for hazard assessment purposes (Anderson et al. 1950).

 

Data on marine organisms is not available.

 

In conclusion, Sn is not acutely toxic to freshwater invertebrates up to concentrations of 38.43 mg Sn/L (unbounded 7 d EC50, nominal total tin, analytically confirmed). Above these concentrations, Sn shows a low acute toxic potential, as indicated by a 48 h EC50 value of 55 mg Sn/L (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.