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Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Read-across statement:

 

No or few ecotoxicological data are available for strontium hydroxide itself. For metals it is generally assumed that toxicity is controlled by the dissolved metal ion. The speciation and chemistry of strontium is rather simple. As a reactive electropositive metal Sr is easily oxidized to the stable and colourless Sr2+ ion in most of its compounds, the chemical behaviour resembling that of Ca and/or Ba (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 asSr2+(Lollar, 2005). Consequently, the toxicity of strontium in the environment is largely controlled by solubility of different Sr-salts (SrCO3,Sr(NO3)2,SrSO4,Sr(OH)2…)

 

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.

Additional information

Short-term toxicity data

Reliable acute data are available for three trophic levels: algae, invertebrates and fish.

·        An unbounded value of >43.3 mg Sr/L was identified for algae.

·        The only bounded acute value of 125 mg Sr/L is available for the invertebrateD. magna.

·        The lowest acute effect value (based on measured Sr in the test medium) was an unbounded value of >40.3 mg Sr/L for the fishC. carpio.

It should be noted that the actual E(L)C50values for fish and algae may be well above the reported values as not even partial effects (i.e., mortality or growth rate inhibition) were noted at the highest test concentrations.The table below provides an overview of the most sensitive, reliable, short-term toxicity freshwater data available for strontium.

Table: Most sensitive reliable short-term toxicity endpoints for strontium in freshwater

 Species

Parameter 

Endpoint 

Value (mg Sr/L) 

Reference 

Acute fish data 

 

 

 

 

 Cyprinus carpio

mortality 

96h-LC50

> 40.3

Tobor-Kaplon (2010) 

Acute invertebrate data 

 

 

 

 

Daphnia magna 

mortality/immobility 

48h-LC50 

125 

Biesinger and Christensen (1972) 

Algal data 

 

 

 

 

Pseudokirchneriella subcapitata 

growth rate 

72h-ErC50 

> 43.3

Tobor-Kaplon (2010)

 

Long-term toxicity data

Reliable studies on chronic toxicity of strontium to the aquatic environment are available for three trophic levels: algae, invertebrates and fish. The toxicity tests were performed using strontium nitrate or strontium chloride hexahydrate as test substance.

  ·        In the study of growth inhibition of the algal speciesPseudokirchneriella subcapitataby strontium nitrate to,all significant effect levels (acute and chronic) were equal or higher than 43.3 mg Sr/L (conservative value). Thus, the 72-h NOEC is ≥ 43.3 mg Sr/L.

·        The study on the chronic toxicity of strontium to invertebrates (Biesinger and Christensen, 1972) reported a calculated NOEC forDaphnia magna(i.e., EC16/2) of 21 mg Sr/L.

·        A chronic fish study according to OECD 210 (Egeler and Morlock, 2013) was performed withDanio rerio. The NOEC (nominal) was set to ≥100 mg/L for strontium nitrate, corresponding to a re-calculated NOEC (nominal) for strontium of ≥ 41.4 mg/L.

 

The PNECaquaticcalculation will be conducted using the assessment factors method since a large dataset from long-term tests for different taxonomic groups is not available, a Species Sensitivity Distribution (SSD) cannot be developed and statistical extrapolation methods can thus not be used to derive the PNECaquatic. An overview of available long-term data used for PNEC-derivation is provided in the Table below.

Table: Most sensitive reliable long-term toxicity data for strontium in freshwater

Species

Parameter

Endpoint 

Value
(mg Sr/L) 

Reference 

Danio rerio

mortality 

34d-NOEC

≥ 41.4

Egeler and Morlock (2013)

Pseudokirchneriella subcapitata

 

72-h NOECr 

 ≥ 43.3

Tobor-Kaplon (2010) 

Daphnia magna

mortality 

21d-NOEC

21 

Biesinger and Christensen (1972)