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Endpoint:
sediment toxicity: long-term
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Recent, non-GLP published study
Qualifier:
according to guideline
Guideline:
other: Bedard D, Hayton A, Persaud D. 1992. Ontario Ministry of the Environment laboratory sediment biological testing protocol. Toronto, ON, Canada.
Principles of method if other than guideline:
Test protocols of the Ontario Ministry of the Environment were followed [Bedard D, Hayton A, Persaud D. 1992. Ontario Ministry of the Environment laboratory sediment biological testing protocol. Toronto, ON, Canada.].
GLP compliance:
no
Analytical monitoring:
yes
Details on sampling:
A 100 g (wet wt) sample of the Long Point control sediment was analyzed for fluoride. The sediment was placed in a plastic jar and frozen, then freeze-dried using a Labconco Lyph-Lock 6t freeze dryer fitted with a Model 77560 Lyph-Lock Stoppering Tray Dryert (Kansas City, MO, USA) for precise temperature control. After drying, the sample was homogenized using a mortar and pestle. Samples of overlying water (250 ml) from one replicate of each of the 110 and 1100 µg F-/g preliminary spiked sediment tests with P. promelas were collected at the beginning and end of the tests and analyzed for fluoride. Similarly, samples of overlying water were taken on days 0, 12, and 21 from one replicate of each treatment of the spiked sediment tests with mayfly larvae. Laboratory dilution water was also analyzed for fluoride.
Vehicle:
no
Test organisms (species):
other: with Pimephales promelas, Hexagenia limbata, Chironomus tentans and Hyalella azteca.
Details on test organisms:
Pimephales promelas: three replicates of 10 fish (80–110 mg). Fish were fed 1 % of mean body weight per day.
Hexagenia limbata: three replicates of 10 mayfly larvae, three to four months old (5–25 mg), were fed 1 ml Hexagenia diet weekly
Chironomus tentans: three replicates of 15 midge larvae, 10 to 12 d old, were fed 1 ml Hexagenia diet per chamber
Hyalella azteca: three replicates of 10 amphipods (1–7 d-old), fed weekly
Study type:
laboratory study
Test type:
static
Water media type:
freshwater
Type of sediment:
natural sediment
Limit test:
no
Duration:
28 d
Exposure phase:
total exposure duration
Hardness:
160 mg/L
Test temperature:
20 °C
pH:
no data
Dissolved oxygen:
no data
Salinity:
no data
Ammonia:
no data
Nominal and measured concentrations:
Concentrations varied with the test species and ranged from 175 to 5,600 mg F2/g dry
weight.
Details on test conditions:
no data
Reference substance (positive control):
no
Duration:
28 d
Dose descriptor:
other: IC25
Effect conc.:
290.2 other: µg F-/g
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
growth rate
Remarks on result:
other: H. azteca
Duration:
10 d
Dose descriptor:
other: IC25
Effect conc.:
661.4 other: µg F-/g
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
growth rate
Remarks on result:
other: C. tentans
Duration:
21 d
Dose descriptor:
other: IC25
Effect conc.:
1 221.3 other: µg F-/g
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
growth rate
Remarks on result:
other: H. limbata
Duration:
21 d
Dose descriptor:
other: IC25
Effect conc.:
> 5 600 other: µg F-/g
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
growth rate
Remarks on result:
other: P. promelas
Duration:
28 d
Dose descriptor:
LC50
Effect conc.:
1 114.6 other: µg F-/g
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
mortality
Remarks on result:
other: H. azteca
Duration:
21 d
Dose descriptor:
LC50
Effect conc.:
1 652.2 other: µg F-/g
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
mortality
Remarks on result:
other: H. limbata
Duration:
21 d
Dose descriptor:
LC50
Effect conc.:
> 5 600 other: µg F-/g
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
mortality
Remarks on result:
other: P.promelas
Duration:
10 d
Dose descriptor:
LC50
Effect conc.:
> 5 600 other: µg F-/g
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
mortality
Remarks on result:
other: C. tentans

Toxicity of sediment-associated fluoride

No significant difference was observed in survival or growth of juvenile P. promelas exposed for 21 d to nominal concentrations of 1100, 500, and 110 mg F/g dry weight in sediment relative to the Long Point, Lake Erie, control sediment.

Toxicity of sediment-associated fluoride to juvenile Pimephales promelas (250–400 mg wet wt) in 21-d growth and survival tests at 20 °C

Nominal concentration in sediment (µg F/g dry wt) Endpoint and response
Survival Weight change
1,100 100 % + 0.5 % (+ 1.63 mg)
500 98 % + 0.7 % (+ 1.85 mg)
110 100 % - 1.3 % (- 4.15 mg)
5* 95 % + 1.4 % (+ 3.75 mg)

*Measured concentration was 4.62 µg F/g dry weight.

Only two of the 40 control minnows and one minnow in the 500 µg F/g exposure died during the test.

No significant difference was observed in survival or growth of juvenile P. promelas exposed for 21 d to nominal concentrations ranging from 700 to 5600 µg F/g relative to the control sediment.

Only one of the 30 control minnows and three minnows in the 700 µg F/g exposure died during the tests.

The concentration of fluoride in laboratory dilution water was 0.16 mg F/L, with a standard deviation (SD) of 0.10.

Concentrations measured in overlying water from the spiked sediment tests with P. promelas in 1993 and H. limbata in 1994 increased over the duration of the tests.

Concentrations of fluoride (as NaF) in overlying water during 21-d growth and survival tests on spiked sediment with Pimephales promelas and Hexagenia limbata 

Nominal concentration in sediment

(µg F-/g dry wt or ppm)

Concentration measured

in overlying water

(mg/L or ppm)

Conversion

factor

(water to

sediment)*

Day 0

Day 12

Day 21

Control (4.62;H. limbata)

0.169**

0.247

< 0.03

19X

110 (P. promelas)

0.55

3.18

35X

700 (H. limbata)

3.10

11.3

10.4

67X

1100 (P. promelas)

1.87

10.1

109X

1400 (H. limbata)

3.26

13.7

14.0

100X

2800 (H. limbata)

7.89

24.9

26.8

104X

5600 (H. limbata)

17.7

56.8

60.9

92X

*Concentration in water on day 21 used for all exposures except the control, where data from day 12 were used.

**Concentration in laboratory dilution water = 0.16 mg/L (standard deviation = 0.1).

In all tests at nominal exposures of 1100 µg F/g or greater, the concentration of fluoride in overlying water on day 21 was almost exactly one one-hundredth of the original concentration spiked into the sediment.

Validity criteria fulfilled:
yes
Conclusions:
Relative toxicity of fluoride was tested in long-term (10–28 d) growth and survival tests in spiked sediment. Hyalella azteca was the most sensitive species for growth (25 % inhibitory concentration [IC25] = 290.2 µg F/g), followed by C. tentans (IC25 = 661.4 µg F/g), H. limbata ( IC25 = 1221.3 µg F/g), and P. promelas (IC25 = >5600 µg F/g). H. azteca was also the most sensitive species for survival (LC50 = 1114.6 µg F/g), followed by H. limbata (LC50 = 1652.2 µg F/g and P. promelas and C. tentans (LC50 = >5600 µg F/g).
Endpoint:
sediment toxicity: long-term
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
Dipotassium hexafluorotitanate is an inorganic substance which will rapidly dissociate into fluoride, potassium and titanium ions upon dissolution in the environment. However, titanium ions do not remain in solution, only fluoride ions do.
The approach follows scenario 1 of the RAAF (ECHA 2017).

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Source
sodium fluoride (CAS 7681-49-4)
Target
Dipotassium hexafluorotitanate (CAS 1619-27-0)

3. ANALOGUE APPROACH JUSTIFICATION
Since dipotassium hexafluorotitanate rapidly dissociates into fluoride, potassium and titanium ions upon dissolution in the environment, and only fluoride but not titanium ions will remain in solution, it can be assumed that toxicity (if any) will be driven by the fluoride anion. Therefore, full read-across of sediment toxicity data of fluoride based upon a molecular weight conversion is justified. Due to the electronegativity of the fluoride ion, little partition to the sediment can be assumed. It follows that sediment is unlikely to become contaminated and, in turn, this means that the contamination of sediment systems is unlikely. Regarding the toxicity of fluoride in respective long-term (10 – 28 d) growth and survival tests in sediment spiked with sodium fluoride, Hyalella azteca was the most sensitive species for growth (EC25 = 290.2 mg F/kg), followed by Chironomus tentans (EC25 = 661.4 mg F/kg), Hexagenia limbata (EC25 = 1221.3 mg F/kg), and Pimephales promelas (EC25 = >5600 mg F/kg). Hyalella azteca was also the most sensitive species for survival (LC50 = 1114.6 mg F/kg), followed by Hexagenia limbata (LC50 = 1652.2 mg F/kg) and Pimephales promelas and Chironomus tentans (LC50 > 5600 mg F/kg for both). Thus, long-term toxicity data are available for 4 species, including a mayfly, a midge, and an amphipod. The lowest EC25 of 290.2 mg F/kg derived for the 28-d growth of Hyalella azteca is read-across to dipotassium hexafluorotitanate resulting in an EC25 of 611.2 mg/kg and taken forward to the chemical safety assessment.

4. DATA MATRIX
see attached read-across statement in section 13.2
Reason / purpose for cross-reference:
read-across source
Duration:
28 d
Dose descriptor:
other: IC25
Effect conc.:
290.2 other: µg F-/g
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
growth rate
Remarks on result:
other: H. azteca
Duration:
10 d
Dose descriptor:
other: IC25
Effect conc.:
661.4 other: µg F-/g
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
growth rate
Remarks on result:
other: C. tentans
Duration:
21 d
Dose descriptor:
other: IC25
Effect conc.:
1 221.3 other: µg F-/g
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
growth rate
Remarks on result:
other: H. limbata
Duration:
21 d
Dose descriptor:
other: IC25
Effect conc.:
> 5 600 other: µg F-/g
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
growth rate
Remarks on result:
other: P. promelas
Duration:
28 d
Dose descriptor:
LC50
Effect conc.:
1 114.6 other: µg F-/g
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
mortality
Remarks on result:
other: H. azteca
Duration:
21 d
Dose descriptor:
LC50
Effect conc.:
1 652.2 other: µg F-/g
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
mortality
Remarks on result:
other: H. limbata
Duration:
21 d
Dose descriptor:
LC50
Effect conc.:
> 5 600 other: µg F-/g
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
mortality
Remarks on result:
other: P.promelas
Duration:
10 d
Dose descriptor:
LC50
Effect conc.:
> 5 600 other: µg F-/g
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
mortality
Remarks on result:
other: C. tentans

Toxicity of sediment-associated fluoride

No significant difference was observed in survival or growth of juvenile P. promelas exposed for 21 d to nominal concentrations of 1100, 500, and 110 mg F/g dry weight in sediment relative to the Long Point, Lake Erie, control sediment.

Toxicity of sediment-associated fluoride to juvenile Pimephales promelas (250–400 mg wet wt) in 21-d growth and survival tests at 20 °C

Nominal concentration in sediment (µg F/g dry wt) Endpoint and response
Survival Weight change
1,100 100 % + 0.5 % (+ 1.63 mg)
500 98 % + 0.7 % (+ 1.85 mg)
110 100 % - 1.3 % (- 4.15 mg)
5* 95 % + 1.4 % (+ 3.75 mg)

*Measured concentration was 4.62 µg F/g dry weight.

Only two of the 40 control minnows and one minnow in the 500 µg F/g exposure died during the test.

No significant difference was observed in survival or growth of juvenile P. promelas exposed for 21 d to nominal concentrations ranging from 700 to 5600 µg F/g relative to the control sediment.

Only one of the 30 control minnows and three minnows in the 700 µg F/g exposure died during the tests.

The concentration of fluoride in laboratory dilution water was 0.16 mg F/L, with a standard deviation (SD) of 0.10.

Concentrations measured in overlying water from the spiked sediment tests with P. promelas in 1993 and H. limbata in 1994 increased over the duration of the tests.

Concentrations of fluoride (as NaF) in overlying water during 21-d growth and survival tests on spiked sediment with Pimephales promelas and Hexagenia limbata 

Nominal concentration in sediment

(µg F-/g dry wt or ppm)

Concentration measured

in overlying water

(mg/L or ppm)

Conversion

factor

(water to

sediment)*

Day 0

Day 12

Day 21

Control (4.62;H. limbata)

0.169**

0.247

< 0.03

19X

110 (P. promelas)

0.55

3.18

35X

700 (H. limbata)

3.10

11.3

10.4

67X

1100 (P. promelas)

1.87

10.1

109X

1400 (H. limbata)

3.26

13.7

14.0

100X

2800 (H. limbata)

7.89

24.9

26.8

104X

5600 (H. limbata)

17.7

56.8

60.9

92X

*Concentration in water on day 21 used for all exposures except the control, where data from day 12 were used.

**Concentration in laboratory dilution water = 0.16 mg/L (standard deviation = 0.1).

In all tests at nominal exposures of 1100 µg F/g or greater, the concentration of fluoride in overlying water on day 21 was almost exactly one one-hundredth of the original concentration spiked into the sediment.

Validity criteria fulfilled:
yes
Conclusions:
Relative toxicity of fluoride was tested in long-term (10–28 d) growth and survival tests in spiked sediment. Hyalella azteca was the most sensitive species for growth (25 % inhibitory concentration [IC25] = 290.2 µg F/g), followed by C. tentans (IC25 = 661.4 µg F/g), H. limbata ( IC25 = 1221.3 µg F/g), and P. promelas (IC25 = >5600 µg F/g). H. azteca was also the most sensitive species for survival (LC50 = 1114.6 µg F/g), followed by H. limbata (LC50 = 1652.2 µg F/g and P. promelas and C. tentans (LC50 = >5600 µg F/g).

Description of key information

Since dipotassium hexafluorotitanate rapidly dissociates into fluoride, potassium and titanium ions upon dissolution in the environment, and only fluoride but not titanium ions will remain in solution, it can be assumed that toxicity (if any) will be driven by the fluoride anion. Therefore, the lowest EC25 of 290.2 mg F/kg derived for the 28-d growth of Hyalella azteca is read-across to dipotassium hexafluorotitanate resulting in an EC25 of 611.2 mg/kg dw and is taken forward to the chemical safety assessment.

Key value for chemical safety assessment

Additional information

Since dipotassium hexafluorotitanate rapidly dissociates into fluoride, potassium and titanium ions upon dissolution in the environment, and only fluoride but not titanium ions will remain in solution, it can be assumed that toxicity (if any) will be driven by the fluoride anion. Therefore, full read-across of sediment toxicity data of fluoride based upon a molecular weight conversion is justified. Due to the electronegativity of the fluoride ion, little partition to the sediment can be assumed. It follows that sediment is unlikely to become contaminated and, in turn, this means that the contamination of sediment systems is unlikely. Regarding the toxicity of fluoride in respective long-term (10 – 28 d) growth and survival tests in sediment spiked with sodium fluoride, Hyalella azteca was the most sensitive species for growth (EC25 = 290.2 mg F/kg), followed by Chironomus tentans (EC25 = 661.4 mg F/kg), Hexagenia limbata (EC25 = 1221.3 mg F/kg), and Pimephales promelas (EC25 = >5600 mg F/kg). Hyalella azteca was also the most sensitive species for survival (LC50 = 1114.6 mg F/kg), followed by Hexagenia limbata (LC50 = 1652.2 mg F/kg) and Pimephales promelas and Chironomus tentans (LC50 > 5600 mg F/kg for both). Thus, long-term toxicity data are available for 4 species, including a mayfly, a midge, and an amphipod. The lowest EC25 of 290.2 mg F/kg derived for the 28-d growth of Hyalella azteca is read-across to dipotassium hexafluorotitanate resulting in an EC25 of 611.2 mg/kg and taken forward to the chemical safety assessment.