Calcium fluoride

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 from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Published, guideline study

Justification for type of information:

A read-across justification is provided in section 13.

Reason / purpose for cross-reference:

read-across source

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material:
Sodium fluoride is water soluble and will rapidly dissociate under the aqueous conditions of the test to form sodium and fluoride ions. The toxicity of sodium fluoride is essentially due to fluoride ions and therefore is appropriate for read-across to CaF2.

Nominal and measured concentrations:

Measured

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

>= 53.37 - <= 98.59 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Remarks on result:

other: above water solubility of CaF2

Details on results:

Benthic larvae were very sensitive to the concentration of fluoride ion with EC50 values ranging from 26 to 48 mg F-/L (actual concentration). Using the molecular weight information, this corresponds to 53.37 to 98.59 mg CaF2/L.

Results with reference substance (positive control):

Not applicable.

Reported statistics and error estimates:

No reported statistics or estimations.

Benthic larvae were found to be sensitive to the concentration of fluoride ion with EC50 values ranging from 26 to 48 mg F-/L (actual concentration). These organisms appear more sensitive than D. magna according to the EU RAR for hydrogen fluoride; however this may be a reflection of the fact that the study was performed with soft water. Using the molecular weight information, this corresponds to 53.37 to 98.59 mg CaF2/L.

Validity criteria fulfilled:

not applicable

Conclusions:

Benthic larvae were very sensitive to the concentration of fluoride ion with EC50 values ranging from 26 to 48 mg F-/L (actual concentration). Using the molecular weight information, this corresponds to 53.37 to 98.53 mg CaF2/L.

Executive summary:

Benthic larvae (Chimarra marginata, Hydropsyche lobata, Hydropsyche bulbifera, Hydropsyche exocellata and Hydropsyche pellucidula) collected in Spanish rivers were found to be sensitive to the concentration of fluoride ion with EC50 values ranging from 26 to 48 mg/L (actual concentration). These organisms appear more sensitive than D. magna according to the EU RAR for hydrogen fluoride; however this may be a reflection of the fact that the study was performed with soft water. Using the molecular weight information, this corresponds to EC50 values ranging from 53.37 to 98.59 mg CaF2/L.

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

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

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Review of available data

Justification for type of information:

A read-across justification is provided in section 13.

Reason / purpose for cross-reference:

read-across source

Post exposure observation period:

No post exposure observation period.

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

>= 53.4 - <= 98.59 mg/L

Nominal / measured:

not specified

Conc. based on:

test mat.

Remarks on result:

other: benthic trichoptera larvae

Remarks:

above water solubility of CaF2

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

199.23 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks on result:

other: Daphnia magna

Remarks:

above water solubility of CaF2

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

314 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks on result:

other: Daphnia magna

Remarks:

above water solubility of CaF2

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

722.99 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks on result:

other: Daphnia magna

Remarks:

above water solubility of CaF2

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

554.6 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks on result:

other: Daphnia sp.

Remarks:

above water solubility of CaF2

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

21.6 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks on result:

other: Mysidopsis bahia (marine)

Remarks:

close to water solubility of CaF2

Duration:

120 h

Dose descriptor:

EC50

Effect conc.:

>= 41 - <= 80 mg/L

Nominal / measured:

estimated

Conc. based on:

test mat.

Remarks on result:

other: Perna perna (marine)

Remarks:

above water solubility of CaF2

Details on results:

The EC50 values for daphnids range from 97 to 352 mg/L and are based on nominal concentrations. Using the molecular weight information, this corresponds to an EC 50 range of 199 to 723 mg CaF2/L.

Results with reference substance (positive control):

Not applicable

Reported statistics and error estimates:

None reported

The reported EC50 values for daphnids range from 97-352 mg F-/L and are based on nominal concentrations. Water hardness in these studies ranged from 173 to 250 mg CaCO3/L. The EU RAR for hydrogen fluoride notes the existence of additional EC50 values in the range 109 to 340 mg F-/L, cited in the RIVM Integrated Criteria Document Fluoride (Sloof et al, 1988). EC50 values of 10.5 -39 mg F-/L are reported for marine invertebrates.

Validity criteria fulfilled:

not specified

Conclusions:

The EC50 values for daphnids exposed to sodium fluoride range from 97 to 352 mg F-/L. Using the molecular weight information, this corresponds to an EC 50 range of 199 to 772.5 mg CaF2/L.

Executive summary:

The EU RAR reviews and summairses the available data on short-term toxicity to aquatic invertebrates. Reported EC50 values for Daphnia spp. range from 97-352 mg/L and are based on nominal concentrations. Using the molecular weight information, this corresponds to an EC 50 range of 199 to 723 mg CaF2/L.

Reference 3

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

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

Adequacy of study:

weight of evidence

Justification for type of information:

A read-across justification is provided in section 13.

Reason / purpose for cross-reference:

read-across source

Principles of method if other than guideline:

The purpose of the study was to identify the effect of alkalinity, water hardness and chloride concentration on the LC50 values.

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

>= 16.6 - <= 67.57 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Remarks:

CaF2

Basis for effect:

mortality

Details on results:

There was a decrease in toxicity when hardness, alkalinity and chloride increased proportionately. Alkalinity nor hardness did appear to be a toxicity modifying factor.
Chloride appeared to be the primary toxicity modifying factor to Hyalelalla.

Results with reference substance (positive control):

The toxicity tests met the criteria for acceptable control performance.

Analytical results fluoride:

Measurement of fluoride were in good agreement with target concentrations: (101 +/- 9%) of target. Fluoride levels measured at test termination were 96 +/- 10% of the concentration at test start.

Validity criteria fulfilled:

yes

Conclusions:

The LC50 values for Hyalella ranged from 8.1 to 37.6 mg/L F. Toxicity of fluoride decreased with increasing water hardness, alkalinity and chloride concentration. The major modifying factor is chloride.
Converting the LC50 to CaF2 (using the molecular weight info), the LC50 values ranged from to 16.6 to 77.23 mg/L CaF2.

Executive summary:

In this study the toxicity of fluoride to Hyalella azteca was investigated together with the impact of water quality variables on the toxicity of fluoride. For this reason water hardness, chloride content and the alkalinity of the water were modified.

In the acute toxicity test (96h), the LC50 values ranges from 8.1 to 37.6 mg/L F. There was a decrease in toxicity when hardness, alkalinity and chloride increased proportionately. Overall, chloride appeared to be the major toxicity modifying factor. No to minimal effects were observed for water hardness and alkalinity. Results from this study demonstrate that test results on fluoride toxicity should always be considered together with the water parameters.

At medium hardness, alkalinity and chlorine content (80/20/25), the LC50 at 96 h was 24.8 mg/L F.

As fluoride is the driving element in toxicity, read-across to CaF2 can be made. Converting the LC50 values to CaF2 (using the molecular weight info), the LC50 values ranged from to 16.6 to 77.23 mg/L CaF2. At medium hardness, alkalinity and chlorine content (80/20/25), the LC50 at 96 h was 50.94 mg/L F.

Description of key information

No studies are available for calcium fluoride. Available studies on NaF were used as read-across source.

The chosen key value for freshwater invertebrated was the lowest reported EC50 among all the evaluated studies reported by Percy et al. 2015 on Hyalella azteca after 96h exposure to NaF. The EC50 was 24.8 mg/L F- which converts in 50.94 mg/LCaF2.

Two reliable studies were also avaialable reporting EC50 value for marine invertebrated. The chosen key value was the lowest reported EC50 in the EU RAR 2001 review on Mysidopsis bahia after 96h exposure. Estimated EC50 was 10.5 mg/L F- which convert in 21.6 mg/L CaF2.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

50.94 mg/L

Marine water invertebrates

Marine water invertebrates

Effect concentration:

21.6 mg/L

Additional information

A weight of evidence approach has been used to evaluate the short-term toxicity to invertebrates. A number of studies have been performed with the water-soluble salt, sodium fluoride and so toxicity of CaF2 was assessed using a read-across method for analogue substance. Effective concentrations were recalculated taking in account the different molecular weight of the source and target substance.

The EU RAR reviews and summarises the available data on short-term toxicity to aquatic invertebrates. The reported EC50 values range from freshwater organisms ranges between 199.23 and 554.6 mg/L CaF2 Differently, EC50s for marine organisms ranged between 21.6 (key value) and 80 mg/L CaF2.

Camargo and Tarazona (1990) studied the effect of NaF on benthic larvae and EC 50 values estimated ranged from 53.4 to 98.59 mg/L CaF2; however the study was performed in soft water.

Pearcy et al. 2015 also investigated the toxicity of NaF to Hyalella azteca. The study shows a decrease in toxicity of fluoride with increasing water hardness, alkalinity and chloride content, with chloride being the major modifying factor. This study confirms that toxicity results should be considered together with information on the water quality.