Strontium oxalate

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Test conducted under GLP according to standard OECD guidelines

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

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 43.3 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 104.7 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 43.3 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 104.7 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 43.3 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 104.7 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 43.3 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 104.7 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Details on results:

No significant differences were recorded between the values for growth rate or yield at the limit concentration, i.e., 100 mg/L when compared to the control group. The growth and yield in lower test concentrations were stimulated rather than reduced/inhibited by the test substance. Microscopic observations at the end of the test revealed a normal and healthy appearance of the exposed cells when compared to the control.
Compliance with the Quality criteria regarding mainenance of actual concentrations was demonstrated by running a test vessel at the highest substance concentrartion but without algae, and samples for analysis were taken at the start, after 24 hours of exposure and at the end of the test period.
Test results were in compliance with all validity criteria (minimum increase in cell density, criteria on variation (growt rates, section-by-section specific growth rates) were not exceeded.

Results with reference substance (positive control):

The 72h-EC50 for growth reduction was 1.2 mg/L (95%CL: 0.77-2.0 mg/L).
The historical range of this value lie between 0.82 and 2.3 mg/L.

Reported statistics and error estimates:

Recorded effects were not significant (< 10%); EC50 values could not be calculated because the test substance proved to be non-toxic within the tested concentration range.
For determination of the NOEC and the EC50 the approaches recommended in the OECD guideline 201 are used. An effect was considered to be significant if statistical analysis of the data obtained for the test concentrations compared with those obtained in the negative control revealed significant reduction of growth rate or yield inhibition (ANOVA, Tukey test, Bonferroni t-test, TOXSTAT Release 3.5, 1996, D.D. Gulley et al).

Percentage reduction of growth rate (total test period)

Nominal Concentration Strontium nitrate (mg/L	Mean growth rate - u (0 -72h)	Mean growth rate - reduction (%)
Control	0.05924
0.10	0.06675	- 12.7
1.0	0.06704	-13.2
10	0.06628	-11.9
100	0.05931	-0.1

Validity criteria fulfilled:

yes

Conclusions:

No statistically significant differences were found between the control and any test item concentration up to and including 100 mg test item/L. The results of the study demonstrate that the EC50 for Pseudokirchneriella subcapitata is >100 mg test item/L. The no-observed effect concentration (NOEC) is ≥104.5 mg/L strontium nitrate (based on measured concentrations). Considering the measured concentrations, the EC50 for Pseudokirchneriella subcapitata is > 43.3 mg Sr/L (measured in the highest concentration at test end). The no-observed effect concentration (NOEC) is ≥ 43.3 mg/L Sr.
Considering that these results are based on dissolved Strontium, they are considered relevant in a read-across approach. Consequently they are used for hazard and risk assessment purposes (classification) for strontium oxalate.

Executive summary:

This study was used in a read-across approach.

The results of the study demonstrate that the EC50 for Pseudokirchneriella subcapitata is >100 mg test item/L. The no-observed effect concentration (NOEC) is ≥104.5 mg/L strontium nitrate (based on measured concentrations). Considering the measured concentrations, the EC50 for Pseudokirchneriella subcapitata is > 43.3 mg Sr/L (measured in the highest concentration at test end). The no-observed effect concentration (NOEC) is ≥ 43.3 mg/L Sr.

These data can be used for hazard and risk assessment purposes (classification) for Strontium oxalate.

Description of key information

One reliable acute/chronic toxicity data point (Klimisch 1, GLP) for an algal species  -the green alga Pseudokirchneriella subcapitata - has been identified.

A 72h-ErC50 and 72h-NOEC of  is reported using  Sr(NO3)2 as test substance.

The measured Sr-levels in solution are based on dissociate strontium. The results are thus considered relevant in a read-across approach on strontium oxalate and these data can be used for hazard and risk assessment purposes (classification) for Strontium oxalate.

Key value for chemical safety assessment

EC50 for freshwater algae:

43.3 mg/L

EC10 or NOEC for freshwater algae:

43.3 mg/L

Additional information

One reliable acute/chronic toxicity data point (Klimisch 1, GLP) for an algal species - the freshwater green alga Pseudokirchneriella subcapitata - has been identified. No effect (growth rate) was noted at the highest (nominal) test concentration of 100 mg test material/L. Based on measured Sr-levels, this effects levels translates to 43.3 mg Sr/L or 104.7 mg strontium nitrate/L.

Therefore, based on measured Sr-levels in solution, the ErC50 and NOEC are >43.3 and >=43.3 mg Sr/L, respectively.