Strontium fluoride

Endpoint summary

Description of key information

Reliable substance-specific information concerning the toxicity for strontium difluoride does not exist. Instead, toxicological information on soluble inorganic fluoride (e.g., sodium) substances and soluble inorganic strontium substances (i.e., strontium dichloride, strontium dinitrate) were extrapolated to strontium(II) fluoride considering that the toxicological effects mainly based on the concentrations of the Sr2+ and F- ions.

Based on the results of the acute toxicity tests it can safely be assumed that the fluoride is the driver for acute toxicity. Hence, LC/LD50 values were re-calculated to strontium difluoride and C&L were given based on these values.

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

166.5 mg/kg bw

Quality of whole database:

reliable key studies for strontium and fluoride are available that enables C&L of strontium difluoride

Acute toxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LC50

Value:

3 000 mg/m³ air

Quality of whole database:

Reliable key study is available for the fluoride anion initiated with sodium fluoride and for soluble strontium substance, strontium dinitrate. Effects were observed for sodium fluoride and the LC50 for sodium fluoride re-calculated to strontium difluoride is 2.99 mg/L. The study conducted with strontium dinitrate resulted in an unbounded LC50 of 4.50 mg/L recalculated to 2.67 mg SrF2/L. Hence, the LC50 value based on the fluoride were used for classification and labelling.

Acute toxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

discriminating dose

Value:

2 000 mg/kg bw

Quality of whole database:

reliable key studies for strontium and fluorides are available that enables C&L of strontium difluoride

Additional information

Reliable substance-specific information concerning the toxicity for strontium difluoride does not exist. Instead, toxicological information on soluble inorganic fluoride (e.g., sodium) substances and soluble inorganic strontium substances (i.e., strontium dichloride and strontium dinitrate) were extrapolated to strontium(II) fluoride considering that the toxicological effects mainly based on the concentrations of the Sr2+ and F- ions.

 

Acute oral toxicity:

In a weight of evidence (WoE) approach the LD50 for fluoride substances in rats and mice was reported to be 166.5 mg SrF2/kg body weight.

By comparison, acute oral toxicity data for strontium rated as reliable provide an LD50 value for Sr(II) of about ≥1484 mg/kg, indicating a much lower class of toxicity than the fluoride anions. Hence, the data for the fluoride anion were taken as the basis for classification purposes.

 

Acute inhalation toxicity:

A study performed with sodium fluoride results in an LC50 of 1,000 mg/m3 that is 2,990 mg/m3 re-calculated to SrF2. The study conducted with strontium dinitrate resulted in an unbounded LC50 of 4.50 mg/L recalculated to 2.67 mg SrF2/L. Hence, the LC50 value based on the fluoride were used for classification and labelling.

 

Acute dermal toxicity:

Neither fluoride nor soluble inorganic strontium substances causes acute dermal toxicity to animals. Hence, LD50 is established to > 2,000 mg SrF2/kg bw.

Justification for classification or non-classification

According to EU classification, labelling and packaging of substances and mixtures (CLP) regulation (EC) no 1272/2008, strontium difluoride should be classified as follows:

Acute oral toxicity Cat. 3: "toxic via ingestion"

Acute inhalation toxicity: Cat. 4 "harmful via inhalation"

Acute dermal toxicity: no C&L