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Ecotoxicological information

Toxicity to microorganisms

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Reference
Endpoint:
toxicity to microorganisms, other
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Justification for type of information:
The reported method includes only a very short exposure time.
Principles of method if other than guideline:
Zr toxicity was assessed with the Microtox TM test reagent (P. phosphoreum) and photometric light-measuring instrument (Model 2055). After being adjusted to 2% NaC1, serial dilutions of the 10 mg L -1 Zr solution were prepared with the Microtox TM diluent. ECs0 (5 rain, 15 °C) light inhibition testing was then performed according to standard procedure outlined in the Beckman Instruments Manual
GLP compliance:
not specified
Analytical monitoring:
not specified
Test organisms (species):
Photobacterium phosphoreum
Test type:
static
Water media type:
freshwater
Limit test:
no
Hardness:
Millipore Super Q water with hardness of < 0.04 mg L -1 in CaCO 3 equivalents
pH:
3.4
Reference substance (positive control):
not specified
Duration:
5 min
Dose descriptor:
EC50
Remarks:
15 C
Effect conc.:
> 4.3 mg/L
Conc. based on:
element
Remarks on result:
other: Effects determined to be due to low pH of ZrCl4 solutions
Details on results:
The Microtox TM (P. phospkoreum) bioluminescent assay initially exhibited a Zr EC50 of 4.3 mg L -1 when tested with a working solution of 10 mg L l (pH = 3.4) prepared with Millipore Super Q dilution water. A second test undertaken with Millipore Super Q water adjusted to the same pH displayed light inhibition virtually identical to that of the 10 mg L -I Zr solution (EC50 = 4.2 mg L -1 Zr). Hence, the toxic effect is, in fact, attributable to pH and not to Zr at the tested concentrations.
Measurable bioluminescence inhibition on this bacterial system is therefore
4.3 mg L -I for this metal.
Using a measured Zr 4+ content of 37% in the anhydrous registered substance, the calculated EC50 is ca 11.6 mg/l.
Conclusions:
Toxic effects identified with the Microtox test were attributed to pH rather than specifically to Zr (5 min. EC50 > 4.3 mg/L)
Executive summary:

The toxicity of zirconium towards bacteria was assessed in the microtox assay. Toxic effects identified with the Microtox test were, however, attributed to pH rather than specifically to Zr (5 min. EC50 > 4.3 mg/L)

Description of key information

Using a measured Zr 4+ content of 37% in the anhydrous registered substance, the calculated EC50 is ca 11.6 mg/l.

Key value for chemical safety assessment

EC50 for microorganisms:
11.6 mg/L

Additional information