Hydroxido potassium zirconium carbonate, where there are 0, 1 or 2 hydroxide groups and 2, 3 or 4 potassium atoms and 2, 3 or 4 carbonate groups.

Short-term toxicity to fish

Description of key information

This endpoint has been addressed using read across where the key study (Goodband & Mullee, 2011) was conducted under GLP conditions and to the OECD guideline 203 and EU method C.1 using ammonium zirconium carbonate as the test material. The Study reported a 96 hour LC50 of >100 % saturated solution for mortality of rainbow trout, conducted as a limit test at 100 % saturated solution.

Additional information

The toxicity of the test material to fish is being addressed using a key study (Goodband and Mullee, 2011) on a surrogate substance, using the read across argument based on its common ionic compounds. Short-term toxicity to fish was investigated in a GLP compliant study on Oncorhynchus mykiss in accordance with the standardised guidelines OECD 203 and EU Method C.1 using the surrogate substance ammonium zirconium carbonate. The study was performed to a good standard with a sufficient level of reporting to be assigned a reliability score of 2 according to the principles for assessing data quality set out in Klimisch (1997).

 

Information provided by the Sponsor indicated that at the pH and concentration used in this study the test item was likely to have become unstable. It is considered likely that the addition of the test item to water resulted in the rapid decomposition of the substance to form zirconium hydroxide, together with accompanying release of carbonate and ammonium ions to the solution. The test item was prepared by stirring an initial 100 mg/L of test item for approximately 10 minutes and then leaving to stand for 24 hours. After the standing period, the preparation was filtered through a 0.2 μm filter (initial approximate 500 mL discarded to pre-condition the filter) and the test organisms exposed to 100 % v/v saturated solution of the decomposition product(s).

 

Following a preliminary range-finding test fish were exposed, in two groups of seven, to an aqueous solution of the test item decomposition product(s), at a single concentration of 100 % v/v saturated solution of decomposition product(s) for a period of 96 hours at a temperature of approximately 14 ºC under semi-static test conditions. The number of mortalities and any sub-lethal effects of exposure in each test and control vessel were determined 3 and 6 hours after the start of exposure and then daily throughout the test until termination after 96 hours.

 

The 96-Hour LC₅₀ based on nominal test concentrations was greater than 100 % v/v saturated solution of decomposition product(s) and correspondingly the No Observed Effect Concentration was 100 % v/v saturated solution of decomposition product(s).

 

Chemical analysis of the test preparations was conducted for zirconium only using ICP-MS.

 

Analysis of the test preparations at 0, 24 and 96 hours showed measured test concentrations to be less than the limit of quantitation (LOQ) of the analytical method employed (which was determined to be 0.053 mg/L). Therefore, the results are based on nominal test concentrations only.

 

At the pH and concentration used in this study the test item is thought to have become unstable. It is considered likely that the addition of the test item to water resulted in the rapid decomposition of the substance to form zirconium hydroxide, together with accompanying release of carbonate and ammonium ions to the solution. The zirconium hydroxide produced is extremely insoluble and would be easily removed from the mixture by the filtration that was performed during the preparation of the test solutions. This is considered to explain the absence of detectable zirconium in the test solutions, as analysed by ICP-MS.

 

This study showed no effects at saturation of the decomposition product(s).

 

Key value for chemical safety assessment

LC₅₀ for freshwater fish: >100 % saturated solution.