Sodium zirconium lactate

Toxicity to microorganisms

Link to relevant study record(s)

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 25 mg/l.

Key value for chemical safety assessment

EC50 for microorganisms:

25 mg/L