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Diss Factsheets

Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Administrative data

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:
ANALOGUE APPROACH JUSTIFICATION
As few data are available on the target substance, a research of the potential analogues has been carried out.
The hypothesis is that properties are likely to be similar or follow a similar pattern as a result of the presence of a common metal ion (or ion complex including a hydrated metal ion). This is a reasonable assumption for the majority of inorganic compounds and some organic compounds (e.g. metal salts of some organic acids).
The following points are be considered:
- Chemical speciation and valency,
- 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.
- Counter ions: the assumption that the metal ion is responsible for the common property or effect implies that the toxicity of the counter ion present in the compound will be largely irrelevant in producing the effects to be assessed.
Based on these data, we have selected the analogue Strontium nitrate.
Strontium has also physiochemical properties similar to calcium and both appear mainly in ionic form in water.

A detail description is provided as attached report of this endpoint in this Iuclid file.
Reason / purpose for cross-reference:
read-across source
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
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.
These data can be used for hazard and risk assessment purposes (classification; PNEC-derivation)
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; PNEC-derivation) for Strontium acetate.

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.

This study was used in a read-across approach and these data can be used for hazard and risk assessment purposes (classification; PNEC-derivation) for Strontium acetate.

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.