Dihydrogen hexafluorotitanate(2-)

Sediment toxicity

Link to relevant study record(s)

Reference

Reference 1

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).

Reference 2

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
Dihydrogen hexafluorotitanate is an inorganic substance which will rapidly dissociate into fluoride, hydrogen and titanium ions upon dissolution in the environment. However, hydrogen and titanium ions do not remain as such 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
Dihydrogen hexafluorotitanate (CAS 17439-11-1)

3. ANALOGUE APPROACH JUSTIFICATION
Since dihydrogen hexafluorotitanate rapidly dissociates into fluoride, hydrogen and titanium ions upon dissolution in the environment, and only fluoride but not hydrogen and titanium ions will remain as such 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 dihydrogen hexafluorotitanate resulting in an EC25 of 417.3 mg/kg dw and is 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 dihydrogen hexafluorotitanate rapidly dissociates into fluoride, hydrogen and titanium ions upon dissolution in the environment, and only fluoride but not hydrogen and titanium ions will remain as such 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 dihydrogen hexafluorotitanate resulting in an EC25 of 417.3 mg/kg dw and is taken forward to the chemical safety assessment.

Additional information

Since dihydrogen hexafluorotitanate rapidly dissociates into fluoride, hydrogen and titanium ions upon dissolution in the environment, and only fluoride but not hydrogen and titanium ions will remain as such 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 dihydrogen hexafluorotitanate resulting in an EC25 of 417.3 mg/kg and taken forward to the chemical safety assessment.