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Short-term toxicity to aquatic invertebrates

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Reference
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
1972
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
Further information in a detailed justification report is included as attachment to the same record.

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
For the determination of analogue in this read-across approach, the following points have been considered:
- Chemical speciation and valency (common strontium cation: Sr2+).
- The water solubility, as it provides a first indication of the availability of the metal ion in the different compartments of interest. The most simplistic approach to hazard evaluation is to assume that the specific metal-containing compound to be evaluated shows the same hazards as the most water-soluble compounds.
- In fluids of organisms and in aqueous media, dissociation of strontium oxalate takes place immediately, resulting in formation of strontium cations (Sr2+) and oxalate anions. Thus, any ingestion or absorption of strontium oxalate by living organisms, in case of systemic consideration, will inevitably result of exposure to the dissociation products.
- Oxalic acid is naturally present in organisms because it is involved in biochemical reactions (Robertson 2011). Oxalic acid occurs widely in nature. It is present in the tissues of many plants and algae (US EPA 1992), serving both to excrete and store calcium. Oxalate anion (formed during the dissociation of strontium oxalate) is of low (eco)toxicological relevance when ingested and taken up systemically. Thus, any possible toxicological or ecotoxicological effect triggered by strontium oxalate exposure can be attributed to strontium.
- Counter ions: the assumption that the metal ion is responsible for the common property or effect implies that the toxicity or ecotoxicity of the counter ion present in the compound will be largely irrelevant in producing the effects to be assessed.
- Likely common breakdown products via physical and/or biological processes for the targeted substance (strontium oxalate) and the analogues identified cannot present strong differences since the structures are very simple and very similar (formation of Sr2+ or oxalate ion).

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Source chemical information is provided in the “source” endpoint. No impurity affecting the classification is reported for the source chemical.
Information on the impurities of the target chemical are detailed in the attached report.

3. ANALOGUE APPROACH JUSTIFICATION
The main hypothesis for the analogue approach are verified. They are presented in the detailed report attached. The experimental data performed on the substance (tests performed in this REACH registration dossier on strontium peroxide) confirms the analogue approach performed (same results on analogues).

4. DATA MATRIX
A data matrix is presented in the detailed report attached.

Reason / purpose for cross-reference:
read-across source
Key result
Duration:
48 h
Dose descriptor:
LC50
Effect conc.:
125 000 µg/L
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
mortality
Remarks:
including immobility
Reported statistics and error estimates:
Results were statistically evaluated with the method of Litchfield and Wilcoxon (1949). LC50 was used for survival and represents an interpolation from three or more partial-effect concentrations.

Chemical characteristics of Lake Superior water were monitored during the testing period according to procedures outlined by the American Public Health Association and procedures employing atomic absorption spectroscopy.

Validity criteria fulfilled:
yes
Conclusions:
Results are based on nominal values, and test did not exacty follow existing guidance (1972-study), but followed test method well described and test conditions (eg. test medium composition) were properly identified. The resulting 48h-EC50 of 125,000 µg Sr/L (endpoint= immobility) is an acceptable value for this endpoint, and can be used for classification purposes. Considering that the result is based on dissolved Sr2+ ion, it is considered acceptable in a read-across purpose.
Executive summary:

SrCl2.6H2O toxicity was investigated on Daphnia magna in a static test during 48h. The relevant effect observed was complete immobilisation or death.

Results are based on nominal values, and test did not exacty follow existing guidance (1972-study), but followed test method well described and test conditions (eg. test medium composition) were properly identified.

Considering that the result is based on dissolved Sr2+ ion, it is considered acceptable in a read-across purpose. The resulting 48h-EC50 of 125,000 ug Sr/L (endpoint= immobility) is an acceptable value for this endpoint, and can be used for classification purposes.

Description of key information

SrCl2.6H2O toxicity was investigated on Daphnia magna in a static test during 48h. The relevant effect observed was complete immobilisation or death.

Results are based on nominal values, and test did not exacty follow existing guidance (1972-study), but followed test method well described and test conditions (eg. test medium composition) were properly identified.

The resulting 48h-EC50 is 125,000 µg Sr/L (endpoint= immobility). This study result was used in a read-across approach considering that they are based on dissolved strontium and thus relevant for strontium oxalate. It considered as an acceptable value for this endpoint, and can be used for classification purposes.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
125 mg/L

Additional information