Strontium sulphate

Endpoint summary

Description of key information

Skin irritation: not irritating (EU B.46; GLP compliant)
Eye irritation: not irritating (OECD 405 (2012; GLP compliant)

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Additional information

Toxicological relevance of the counterion “sulfate”

The registrant is of the opinion that the toxicity of strontium sulfate is driven by the strontium moiety and that the sulfate anion does not contribute to the overall toxicity of the substance strontium sulfate to any relevant extent, for the following reasons:

Sulfate anions are abundantly present in the human body in which they play an important role for the ionic balance in body fluids. Sulfate is required for the biosynthesis of 3′-phosphoadenosine-5′-phosphosulfate (PAPS) which in turn is needed for the biosynthesis of many important sulfur-containing compounds, such as chondroitin sulfate and cerebroside sulfate. The Joint FAO/WHO Expert Committee on Food Additives (JECFA) concludes that the few available studies in experimental animals do not raise any concern about the toxicity of the sulphate ion in sodium sulphate. Sodium sulphate is also used clinically as a laxative. In clinical trials in humans using 2-4 single oral doses of up to 4500 mg sodium sulphate decahydrate per person (9000 – 18000 mg per person), only occasional loose stools were reported. These doses correspond to 2700 - 5400 mg sulphate ion per person. High bolus dose intake of sulphate ion may lead to gastrointestinal discomfort in some individuals. No further adverse effects were reported (JECFA 2000, 2002). This position was adopted by the European Food Safety Authority (EFSA 2004) without alteration.

Based on the above information, one can therefore safely assume that the sulfate anion in strontium sulfate does not contribute to the overall toxicity of strontium, sulfate. It is concluded that only the effect of “strontium” is further considered in the human health hazard assessment of strontium sulfate.

Read across from Sr(NO₃)₂to SrSO₄:

The toxicity of strontium substances such as strontium sulfate can reasonably assumed to be determined by the availability of strontium ions in solution. As a first surrogate for bioavailability, the water solubility of a test substance may be used. Strontium nitrate is highly water soluble with ≤ 802 g/L at pH ~ 7, whereas strontium sulfate is moderately soluble (~125 mg/L at pH ~ 6.5). Hence, any read across from strontium nitrate to strontium sulfate is inherently very conservative.

Skin irritation:

A relialbe in vitro skin irritation study strontium nitrate according to EU B.46 (k_Verbaan_2010) is results indicate that strontium nitrate and therefore strontium sulfate (based on read across) are not irritating to the skin.

Eye irritation:

A reliable in vivo eye irritation study according to OECD 405 (k_Hansen_2014) was performed with strontium sulfate.Results indicate that strontium sulfate is not irritating to the eye.

Justification for selection of skin irritation / corrosion endpoint:
GLP guideline study conducted with a structural analogue (strontium nitrate)

Justification for selection of eye irritation endpoint:
GLP guideline study conducted with the test item

Justification for classification or non-classification

Skin irritation:

Strontium sulfate does not possess a skin irritation potential and does not require classification as skin irritant according to Directive67/548/EEC and its subsequent amendments and Regulation (EC) No 1272/2008 and subsequent regulations..

 

Eye irritation:

Strontium sulfate does not possess an eye irritation potential and does not require classification as eye irritant according to Directive67/548/EEC and its subsequent amendments and Regulation (EC) No 1272/2008 and subsequent regulations.

Respiratory irritation:

The classification as respiratory irritant is covered under the endpoint specific target organ toxicity- single exposure and repeated exposure. Please refer to the endpoint summaries on acute toxicity (endpoint 7.2) and repeated dose toxicity (endpoint 7.5) for further information.