Strontium chloride

Endpoint summary

Description of key information

Acute toxicity, oral: LD50 > 2000 mg/kg bw
Acute toxicity, inhalation: LC50 > 3.4 mg/L +- 0.4 mg/L (calculated from strontium nitrate)
Acute toxicity, dermal: data waiving

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Acute toxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Acute toxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Acute inhalation toxicity – read across

Acute inhalation toxicity data or strontium chloride are not available. It was decided to read across from strontium nitrate (LC50 >= 4.5 mg/L +- 0.6 mg/L) to strontium chloride (calculated LC50 3.4 mg/L+- 0.4 mg/L) and to not C&L strontium chloride for the following reason:

(i) acute inhalation toxicity of strontium nitrate: This study was performed with a maximum attainable concentration of 4.5 mg/L +- 0.6 mg/L strontium nitrate. Because of the extremely coarse nature of the test material (d50>300 µm), the investigators chose to formulate the test item in water, and to administer it via inhalation as an aqueous aerosol. In the study, only one out of ten animals died within the observation period (after 2 hours after start of exposure). The investigators conclude that the LC50 of strontium nitrate under these exposure conditions can safely be assumed to be > 5 mg/L. Considering the extremely coarse particle size of solid, crystalline strontium nitrate, then the LC₅₀of solid strontium nitrate can also be assumed to be well above 5 mg/L.

 

(ii) relative bioavailability of strontium substances:  strontium chloride and strontium nitrate are highly soluble in water (ca. 538 g/L; pH ca. 7.0 and ca. 667 g/L; pH ca. 6, respectively).  Thus, read-across from the nitrate to the chloride is fully justified, since the bioavailability of the chloride could be regarded as identical.

 

(iii)  particle size considerations: whereas the “physical” particle size (d50 measured after dry dispersion by laser diffraction) indicates that strontium nitrate is much coarser than the commercial grade of strontium chloride, a more refined analysis involving cascade impactor particle size analysis of the airborne fraction in a rotating drum dustiness test with subsequent modelled deposition in the respiratory tract (see table below) demonstrates that under conditions of practical handling and use, both materials show a similar deposition pattern to expected after inhalation exposure, with roughly similar inhalation absorption rates (ranging from 8.9-9.1%).

 

							deposition fractions			absorption factors		absorption factor via inhalation [%]
Sample	rel. Density	D50 [µm]	MMAD 1 [µm]	GSD 1	MMAD 2 [µm]	GSD 2	Head [%]	TB [%]	PU [%]	Head/TB (=GI) [%]	PU [%]
SrCL2	3.1 at 20°C	182.4	4.24 (10%)	4.48	32.74 (90%)	1.54	42.28	0.25	0.57	20.00	100.00	9.10
Sr(NO3)2	3.0 at 19°C	314.5	30.30	1.54	na	na	44.46	0.04	0.01	20.00	100.00	8.91

 

In conclusion, based on particle size and relative bioavailability considerations, read across from strontium nitrate to strontium chloride is considered to be reasonable without restriction, and also to imply an inherent conservatism, so that the LC50 of strontium chloride may reasonably be assumed to be > 5 mg/L. According to the regulation (EC) 1272/2008 the threshold value for LC50 is > =5 mg/L. Hence, the test substance does not meet the criteria for classification and labelling according to GHS.

 

Justification for selection of acute toxicity – oral endpoint
Only one study available.

Justification for selection of acute toxicity – inhalation endpoint
Only one study available.

Justification for selection of acute toxicity – dermal endpoint
waiver

Justification for classification or non-classification

Acute oral toxicity

There is one reliable study for acute oral toxicity testing performed by Notox in 2010 according to the current valid EC guideline. The LD50 was determined to be > 2000 mg/kg bw. Hence, no classification and labelling is required for strontium chloride

 

Specific target organ toxicant (STOT) – single exposure: oral

The classification criteria according to regulation (EC) 1272/2008 as specific target organ toxicant (STOT) – single exposure, oral are not met since no reversible or irreversible adverse health effects were observed immediately or delayed after exposure and no effects were observed at the guidance value, oral for a Category 1 classification of 300 mg/kg bw and at the guidance value, oral for a Category 2 classification of 2000 mg/kg bw in addition to this effects which were responsible for the death of the animals. No classification required.

 

Acute dermal toxicity

Following the HERAG guidance for metals and metal salts (see section 7.1.2 of the technical dossier, dermal absorption), a dermal absorption rate in the range of maximally 0.1-1.0 % can be anticipated. Dermal absorption in this order of magnitude is not considered to be “significant”.

In conclusion, testing for acute toxicity of strontium chloride via the dermal route is not required according the criteria laid down in Annex VIII, point 8.5.

Thus, concerning dermal toxicity of strontium nitrate, following the criteria specified by Directive 67/548/EEC and subsequent regulations, the test item shall not be classified as acutely toxic via the dermal route. According to the EC Regulation No. 1272/2008 and subsequent regulations, the test item is not to be classified.

 

Acute inhalation toxicity

There is one study on acute toxicity, inhalation available. This study was performed with a limit concentration of 4.5 mg/L +- 0.6 mg/L strontium nitrate which related to a strontium chloride concentration of 3.4 mg/L +- 0.4 mg/L. One out of ten animals died within the observation period (after 2 hours after start of exposure). According to the regulation (EC) 1272/2008 the threshold value for LC50 is > =5 mg/L but due to the reason stated under “discussion” above, classification and labelling according to GHS is not required for strontium chloride

 

Specific target organ toxicant (STOT) – single exposure: inhalation

Laboured respiration was observed for two males between approximately 1.5 and 3.5 hours after start of exposure, including the male that was found dead.

Hunched posture, lethargy, rales, gasping, piloerection, chromodacryorrhoea and/or ptosis were observed among three males mainly between Days 1 and 6 after exposure. Rates were also observed during the second week of the observation period. No clinical signs were noted among the other animals. It can be concluded that these effect observed in two and three animals (out of ten), respectively are not sufficient for classification.