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Key value for chemical safety assessment

Additional information

Genetic toxicity in vitro:

Because there was no relevant and reliable information available for zirconium basic sulfate, read across was performed using studies performed with zirconium basic carbonate and zirconium dioxide, both similar non-soluble zirconium compounds. The read across justification is added in Section 13 of IUCLID.

Bacterial reverse mutation assay:

Two studies are included to cover this endpoint using a weight of evidence approach: one study performed with zirconium basic carbonate and a second one with zirconium dioxide.

BIBRA (1987) performed an Ames test (OECD 471) with Salmonella typhimurium strains TA TA98, TA100, TA1535, TA1537 and TA1538 with and without metabolic activation. The test substance was zirconium basic carbonate, a similar non-soluble zirconium compound.

Following concentrations were tested:

Method 1: 0, 1, 10, 100, 1000, 10000 µg/plate (preliminary toxicity study)

Method 2: 0, 0.2, 1.0, 5.0, 20.0, 100 µg/plate (plate incorporation test)

Method 3: 0, 0.2, 1.0, 5.0, 20.0, 100 µg/plate (plate incorporation test)

Method 4: 0, 0.2, 1.0, 5.0, 20.0, 100 µg/plate (liquid incubation test)

Number of replicates tested: Method 1: duplicate; Method 2: triplicate; Method 3: triplicate; Method 4: triplicate.

No increase in the number of revertants was seen in either of the strains, with or without S-9, with exposure to the test substance.

Negative controls and positive controls were run in parallel and were considered to be valid.

According to the results of the study, the test substance is not mutagenic in the Ames test with and without metabolic activation.

The abovementioned study was performed according to the OECD 471 guideline adopted in 1983 where only 4 strains were required (not including Salmonella typhimurium strain TA102 or E. coli strain). Although the test is reliable and relevant to cover this endpoint, the strains used may not detect certain oxidising mutagens, cross-linking agents and hydrazines. Therefore, read across to zirconium dioxide, another water insoluble zirconium compound, is added in the weight of evidence approach.

LAUS (2008) performed a bacterial reverse mutation study according to OECD guideline 471. Salmonella typhimurium strains TA97a, TA98, TA100, TA102 and TA1535 were exposed to the read across substance zirconium dioxide at concentrations between 50 to 4998 µg/plate with and without metabolic activation in two independent experiments. Vehicle and positive controls were valid. Zirconium dioxide did not induce mutation with and without metabolic activation and no cytotoxicity was observed.

Based on the abovementioned data and applying a weight of evidence approach, it can be concluded that zirconium basic sulfate is not expected to be mutagenic to bacteria with and without metabolic activation.

Both studies were scored as reliable with restrictions (Klimisch 2) to reflect the read across status.

 

In vitro cytogenicity in mammalian cells:

Again, two studies were included in a weight of evidence approach to cover this endpoint: one performed with zirconium basic carbonate and the other with zirconium dioxide.

Ciliutti (2013) performed an in vitro Chromosome Aberration test in Chinese hamster ovary cells (OECD 473). The test substance was zirconium basic carbonate, a similar non-soluble zirconium compound. Two experiments were performed using different test concentrations (10 different concentrations up to and including 5.35 mM; corresponding to 3038 µg/mL zirconium basic carbonate hydrate and 1650 µg/mL zirconium basic carbonate anhydrous

with and without S9 activation (3h exposure and harvested at 20h in experiment I; continuous exposure until harvest at 20h for experiment II). Both negative and positive controls were considered to be valid. On the basis of the results obtained, it was concluded that zirconium basic carbonate did not induce structural chromosome aberrations after in vitro treatment and under the reported conditions.

NOTOX B.V. (2010a) also performed a chromosome aberration test according to OECD guideline 473. The test substance was zirconium dioxide, another similar non-soluble zirconium compound. Cultured peripheral human lymphocytes were exposed for 3 hours to 10, 33 and 100 µg zirconium dioxide/mL culture medium with and without S9-mix (dose range finding test/first cytogenetic assay); at 24 and 48 h continuous exposure time blood cultures were treated with 1, 3, 10, 33, 100, 333 and 1000 µg zirconium dioxide/mL culture medium without S9-mix. A second cytogenicity test was performed as follows: without S9-mix: 10, 33 and 100 µg/mL culture medium (24 and 48 h exposure time, 24 h and 48 h fixation time); with S9-mix: 10, 33 and 100 µg/mL culture medium (3 h exposure time, 48 h fixation time). Vehicle and positive control substances were tested simultaneously and considered valid. Zirconium dioxide tested negative with and without metabolic activation. No cytotoxicity was observed.

Based on the abovementioned data and applying a weight of evidence approach, it can be concluded that zirconium basic sulfate is not expected to be cytotoxic in mammalian cells with and without metabolic activation.

Both studies were scored as reliable with restrictions (Klimisch 2) to reflect the read across status.

In vitro mammalian cell gene mutation:

Finally, one in vitro mammalian cell gene mutation study (performed with zirconium dioxide) was added to the overall weight of evidence approach for genetic toxicity.

NOTOX B.V. (2010b) performed a mouse lymphoma assay (MLA) with the read across substance zirconium dioxide according to OECD guideline 476. In this study mouse lymphoma L5178Y cells were exposed to 0.03, 0.1, 1, 3, 10, 33 and 100 µg/mL zirconium dioxide with and without metabolic activation. In a first experiment, cell cultures were exposed for 3 hours to zirconium dioxide in exposure medium in the absence and presence of S9-mix. In a second experiment, cell cultures were exposed to zirconium dioxide in exposure medium for 24 hours in the absence of S9-mix and for 3 hours in the presence of S9-mix. Zirconium dioxide tested negative in both experiments with and without metabolic activation. No cytotoxicity was observed and positive and vehicle controls were considered valid. This study was also scored as reliable with restrictions (Klimisch 2) to reflect the read across status. Based on the results of this study zirconium basic sulfate, which is a similar non-soluble zirconium compound, is not expected to cause gene mutations in mammalian cells either.

Genetic toxicity in vivo:

According to REACH Annex IX section 8.4, column 2, no further in vivo testing is required as no positive results were obtained in any of the three types of in vitro studies performed according to REACH Annexes VII and VIII section 8.4.


Justification for selection of genetic toxicity endpoint
There are 5 in vitro studies available (read across from zirconium basic carbonate and zirconium dioxide, two other water insoluble zirconium compounds). These 5 studies are used in a weight of evidence approach to cover the endpoint.

Short description of key information:
Genetic toxicity in vitro:
Bacterial reverse mutation assay:
Two studies are used (weight of evidence). One study was performed with zirconium basic carbonate (a similar non-soluble zirconium compound) according to OECD guideline 471 in S. typhimurium TA98, TA100, TA1535, TA1537 and TA1538 (BIBRA, 1987). The test item was not mutagenic with and without metabolic activation. A second study (LAUS, 2008) was performed with zirconium dioxide (another similar non-soluble zirconium compound) according to OECD guideline 471. The substance was negative with and without metabolic activation in S. typhimurium strains TA97a, TA98, TA100, TA102 and TA1535.

In vitro cytogenicity in mammalian cells:
Again, two similar studies, performed according to OECD guideline 473 with read across substances zirconium dioxide and zirconium basic carbonate, are used in a weight of evidence approach (NOTOX, 2010a; Ciliutti, 2013). Both test items were not clastogenic with and without metabolic activation.

In vitro mammalian cell gene mutation test:
One study was included, performed according to OECD guideline 476 with the read across substance zirconium dioxide (NOTOX, 2010b). Zirconium dioxide was found to be negative in mouse lymphoma L5178Y cells with and without metabolic activation.

Genetic toxicity in vivo:
According to REACH Annex IX section 8.4, column 2, no further in vivo testing is required as no positive results were obtained in any of the three types of in vitro studies performed according to REACH Annexes VII and VIII section 8.4.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

Based on the available data from the read across substances zirconium dioxide and zirconium basic carbonate and according to the criteria of the CLP Regulation, zirconium basic sulfate should not be classified for mutagenicity.