Strontium sulphate

Long-term toxicity to aquatic invertebrates

Description of key information

One reliable chronic toxicity study was identified.  Biesinger and Christensen reported a 21d-EC16 of 42 mg Sr/L (nominal values), which can be used for the estimation of a NOEC-value of 21 mg Sr/L (i.e., EC16/2; ECHA-guidance).

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

44 mg/L

Additional information

Read-across statement:

In the aqueous and terrestrial environment, strontium sulfate dissolves in (pore) water releasing strontium cations and sulfate anions.

Sulfate:Sulfates are of low environmental toxicity (OECD SIDS for Na₂SO₄) as sulfate is essential to all living organisms and their intracellular and extracellular concentrations are actively regulated.

Strontium: No or few ecotoxicological data are available for strontium sulfate itself. For the assessment of the environmental fate and behaviour of strontium substances, a read-across approach is applied based on all information available for inorganic strontium compounds. This is based on the common assumption that after emission of metal compounds into the environment, the moiety of toxicological concern is the potentially bioavailable metal ion (i.e., Sr²⁺).This assumption is considered valid as the ecotoxicity is only affected by the strontium-ion and not by the counter (sulfate) ion.The speciation and chemistry of strontium is rather simple.

 

As reactive electropositive metal, strontium is easily oxidized to the stable and colourless Sr²⁺ion in most of its compounds, the chemical behaviour resembling that of calcium and/or barium (Wennig and Kirsch, 1988). In the environment, the element only occurs in one valence state (Sr²⁺), does not form strong organic or inorganic complexes and is commonly present in solution as Sr²⁺(Lollar, 2005). Consequently, the transport, fate, and toxicity of strontium in the environment are largely controlled by solubility of different Sr-salts (e. g., SrCO₃, Sr(NO₃)₂, SrSO₄, …).

These findings are sufficient justification for the implementation of a read-across strategy with ecotoxicity results obtained in tests that were conducted with different strontium compounds that generate free Sr²⁺-ions in solution, and this for all relevant environmental endpoints that were considered.

In sum, the environmental hazard assessment is based on strontium.

References:Wennig, R.; Kirsch, N. (1988): Chapter 57 Strontium, In: Seiler, U. G. et al.(eds), Handb. Tox. Inorg. Comp. NY, 631-638

Summary: According to ECHA Guidance, a NOEC can be estimated by dividing a reliable EC_X by 2, and this when X is situated between 10 and 20 % effect. The 21d-EC₁₆ of 42 mg Sr/L for D. magna, as reported by Biesinger and Christensen (1972) is in compliance with this criterion. Therefore a NOEC of 21 mg Sr/L could be derived for the freshwater compartment (NOEC=EC16/2). Re-calculation to strontium sulfate resulted in an NOEC of 44.0 mg SrSO4/L.