Strontium

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to fish

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP-test conducted according to standard guidelines

Justification for type of information:

Strontium metal is highly reactive and instantly oxidizes upon contact with water. It decomposes completely. During the redox-reaction with water, a strong evolution of hydrogen gas and an immediate precipitation of a white, crystalline solid (i.e. Sr(OH)2) is observed (Sr2+ + 2OH- + H2 (g). The amount of dissolved Sr cations is determined by the solubility of the Sr(OH)2 precipitate. According to OECD guideline 105 (1995) and EU method A.6 (2006), the water solubility of strontium was determined to be 6.74 ± 0.14 g/L under the conditions of the test (flask method under protective gas atmosphere; loading of 41 g Sr/L, at 20.0 ± 1.0 °C, pH >13).
Due to the buffering capacity of most environmental systems, it may reasonable be assumed that the formed hydroxide ions are neutralised in the environment by different processes including precipitation.
The solubility of strontium is not greatly affected by the presence of most inorganic anions as there is little tendency for strontium to form complexes with inorganic ligands (Krupka et al. 1999. EPA 402-R-99-004B and references therein). Free Sr2+ cations are mobile under most environmental conditions, despite the relatively low solubility of strontium carbonate and strontium sulfate at neutral to high pHs. In solutions with a pH below 4.5, the Sr2+ ion is dominant. Under more neutral conditions (pH 5 to 7.5), SrSO4 forms. Strontium carbonate controls strontium concentrations in solutions only under highly alkaline conditions. Further, dissolved strontium forms only weak aqueous complexes with chloride and nitrate (Salminen et al. 2015 and references therein, Krupka et al. 1999. EPA 402-R-99-004B). Regarding monodentate and bidentate binding to negatively-charged oxygen donor atoms, including natural organic matter, alkaline earth metals, such as strontium, tend to form complexes with ionic character as a result of their low electronegativity. Ionic bonding is usually described as resulting from electrostatic attractive forces between opposite charges, which increase with decreasing separation distance between ions (Carbonaro and Di Toro. 2007. Geochim Cosmochim Acta 71 3958–3968; Carbonaro et al. 2011. Geochim Cosmochim Acta 75: 2499-2511 and references therein). Thus, strontium does not form strong complexes with fulvic or humic acids based on the assumption that strontium would exhibit a similar (low) stability with organic ligands as calcium and that strontium could not effectively compete with calcium for exchange sites because calcium would be present at much greater concentrations (Krupka et al. 1999. EPA 402-R-99-004B). In sum, strontium ions are highly mobile, occur only in one valence state (2+), i.e. are not oxidized or reduced, and do not form strong complexes with most inorganic and organic ligands (Krupka et al. 1999. EPA 402-R-99-004B; Salminen et al. 2015). Thus, it may further be assumed that the behaviour of the dissociated strontium ions in the environment determine the fate of strontium upon dissolution with regard to (bio)degradation, bioaccumulation, partitioning as well as the distribution in environmental compartments (water, air, sediment and soil) and subsequently the ecotoxicological potential.Therefore, the assessment of the ecotoxicity of strontium is based on elemental strontium concentrations. Read-across of ecotoxicity data available for soluble strontium substances is applied since the strontium ions determine the ecotoxicological potential of strontium.

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

Principles of method if other than guideline:

Procedures were designed to meet the test methods of the Commission Regulation (EC) No 440/2008, Part C.1, 2008 and the ISO International Standard 7346-1: static method, 1996.

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Samples for possible analysis were taken from the limit concentration and the control:- frequency: at t=0 and t=96h- volume: 4.8 mL- storage: samples were stored in a freezer until analysis

Details on test solutions:

Adjusted ISO medium

Test organisms (species):

Cyprinus carpio

Details on test organisms:

Source: Zodiac, proefacc., "De Haar vissen", Wageningen University and Research Centre, The NetherlandsF1 from a signle parent bred in UV-treated waterrange finding length: 2.2 +/- 0.2 cmfinal test length: 2.5 +/- 0.1 cmrange finding weigth: 0.26 +/- 0.08 gfinal test weigth: 0.40 +/- 0.08 g

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

96

Remarks on exposure duration:

h

Hardness:

211.5 mg/L as CaCl2.2H2O + 88.8 mg/L as MgSO4.7H2O

Test temperature:

control: 20.8 - 21.2100 mg/L: 20.7 -21.2

pH:

pH control: 7.5 - 8.0pH 100 mg/L: 7.5 -7.9

Nominal and measured concentrations:

range finder: 0.1, 1, 10, 100 mg/L as Sr(NO3)2limit test: nominal concentration: 100 mg/L as Sr(NO3)2Measured 100 mg/L: 97.8 mg/L strontium nitrate (t=0h)Measured 100 mg/L: 97.1 mg/L strontium nitrate (t=96h)Measured 100 mg/L (mean): 97.45 mg/L strontium nitrate, i.e., 40.3 mg Sr/L

Details on test conditions:

Vigorous shaking was sufficient to completely dissolve the test substance in mediumTest vessels: 6.5 L; all-glassTest volume per replicate: 6 LControl: test medium without test substance or other additives No of replicates for control and highest test concentration: 1No. of organisms per test concentration: 7Loading: 0.47 g fish/L, i.e., 7 fish per 6 L of test mediumIllumination: 16h photoperiod dailyAeration was introduced tow times between 39-56 and 73-97 hours of exposure? Note that the intriduction of aeration was not necessary for this test but for a simultaneously performed test that shared the control treatmentFeeding: No feeding from 24 hours prior to the test and during the total test period- pH, dissolved oxygen content, temperature: daily in all vessels with surviving fish, beginning at the start of the test. - Mortality and other effects: observations were made at 3 3/4, 24, 48, 72 and 96 hours following the start of te test. In addition, every afternoon for day 0 and every morning from day 1 to observe for any dead or severey distressed fish. Dead fish were removed when observed.

Reference substance (positive control):

yes

Remarks:

pentachlorophenol

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

>= 97.45 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 97.45 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

>= 40.3 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 40.3 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Basis for effect:

mortality (fish)

Details on results:

- Actual concentrations were >80% of the nominal concentrations- No mortality was observed in the control at the end of the test- Test conditions were maintained constant throughout the test- The dissolved oxygen concentration has been at least 60% of the air saturation value throughout the test (>5 mg/L at 22 degrees Celcius).No mortality (0%) was noted in all test concentrations of the range-finding test and the limit test.

Results with reference substance (positive control):

The 96h-LC50 for carp exposed to pentachlorophenol (PCP) was estimated to be 0.15 mg/L (95%CL: 0.10-0.22 mg/L).The range of the 96h-LC50 for carp is generally between 0.10 and 0.46 mg/L based on historical data of reference tests performed approximately every three months from April 1988 until the end of 2000, and annually since then.

Reported statistics and error estimates:

No LC50 could be calculated because the tested concentration of 100 mg/L test substance proved to be non-toxic (LC50 > maximum concentration tested)

Validity criteria fulfilled:

yes

Conclusions:

The LC50 (96 h) based on measured concentrations was higher than 40.3 mg Sr/L.The LC50 (96 h) based on measured concentrations was higher than 97.45 mg strontium nitrate/L.These data can be used for hazard assessment purposes.

Description of key information

One reliable acute toxicity data point (Klimisch 1, GLP) for a fish species  -the carp Cyprinus carpio - has been identified. Based on measured Sr-level in the water column, a 96h-LC50 of >40.3 mg Sr/L  is reported by Tobor-Kaplon (2010), using  strontium nitrate as test substance.

Additional information

One reliable acute toxicity data point (Klimisch 1, GLP) for a fish species -the carp Cyprinus carpio - has been identified. No effect (mortality) was noted at the highest measured test concentration of 40.3 mg/L.