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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
not specified
Analytical monitoring:
yes
Details on sampling:
Not specified
Test organisms (species):
Selenastrum sp.
Details on test organisms:
Selenastrum capricornutum (ATCC 22662 strain).
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
96 h
Hardness:
Millipore Super Q water at a hardness of < 0.04 mg L -1 in CaCO 3 equivalents
pH:
Unadjusted for pH
Nominal and measured concentrations:
Eleven serial dilutions of Zr (10, 5, 2.5, 1.25, 0.625... mg/L
Details on test conditions:
8 replicates were tested for each test concentration and controls. Four such EC50 tests, begun on different days, were carried out.
Duration:
96 h
Dose descriptor:
EC50
Effect conc.:
2.6 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
element
Basis for effect:
not specified
Duration:
96 h
Dose descriptor:
IC50
Effect conc.:
ca. 7 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
other: Calculated for registered substance
Basis for effect:
not specified
Details on results:
The EC50 of 2.6 mg/L is the mean value of four EC50 tests (2.1, 3.8, 2.9, and 1.7 mg L ~) initiated at different times

Further testing to confirm that the effects observed were due to Zr toxicity were also carried out, including ATP energy stress tests. In these tests,

4- and 16-hr EC50's appeared to corroborate the 96-hr EC50 results, indicating that the effects observed were genuinely due to Zr toxicity.

Conclusions:
The EC50 (Selenastrum capricornutum), 96 h) was 2.6 mg/L Zr. Further testing to confirm that the effects observed were due to Zr toxicity were also carried out, including ATP energy stress tests. In these tests, 4- and 16-hr EC50's appeared to corroborate the 96-hr EC50 results, indicating that the effects observed were genuinely due to Zr toxicity.
Using a measured Zr 4+ content of 37% in the anhydrous registered substance, the calculated EC50 is ca 7 mg/l.
Executive summary:

The EC50 (Selenastrum capricornutum), 96 h) was 2.6 mg/L Zr. Further testing to confirm that the effects observed were due to Zr toxicity were also carried out, including ATP energy stress tests. In these tests, 4- and 16-hr EC50's appeared to corroborate the 96-hr EC50 results, indicating that the effects observed were genuinely due to Zr toxicity.

Description of key information

Using a measured Zr 4+ content of 37% in the anhydrous registered substance, the calculated EC50 is ca 7 mg/l.

This figure is used for the PNEC as algae appear to be the most sensitive.

Key value for chemical safety assessment

EC50 for freshwater algae:
7 mg/L

Additional information