Strontium sulphate

Toxicity to microorganisms

Description of key information

One reliable toxicity data point (Klimisch 1, GLP) has been identified for micro-organisms; a respiration inhibition test with activated sludge. Based on total amount of strontium added to the test solution, a  3h-IC50 and 3h-NOEC of >41.4 and >=41.4 mg Sr/L, respectively,  was reported by Desmares-Koopman (2010), using  Sr(NO3)2 as test substance.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

86.8 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: One reliable toxicity data point (Klimisch 1, GLP) with activated sludge from a (predominantly) domestic sewage plant has been reported by Desmares-Koopman (2010). Inhibition of respiration was the endpoint under consideration.

At a nominal concentration of 100 mg Sr(NO₃)₂/L, no inhibition of the respiration rate was noted. Therefore - expressed as mg Sr_total/L, the 3h-IC₅₀and 3h-NOEC were >41.4 and ≥ 41.4 mg/L, respectively. Re-calculation to strontium sulfate leads to a 3h-IC₅₀and 3h-NOEC of >86.8 and ≥ 86.8 mg SrSO₄/L.