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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
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 17% in the anhydrous registered substance, the calculated EC50 is ca 15 mg/l.

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

Sodium and lactate (as lactic acid) are not considered hazardous to aquatic organisms at concentrations leading to classification

Key value for chemical safety assessment

EC50 for freshwater algae:
15 mg/L

Additional information