Reaction product of zirconium (IV) dioxide and zirconium (IV) dicarbonate with nitric acid

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

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 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