2-ethylhexanoic acid, zirconium salt

Endpoint summary

Additional information

Read-across approach

Selected endpoints for the human health hazard assessment are addressed by read-across, using a combination of data on the metal cation and the organic acid anion. This way forward is acceptable, since metal carboxylates are shown to dissociate to the organic anion and the metal cation upon dissolution in aqueous media. No indications of complexation or masking of the metal ion through the organic acid were apparent during the water solubility and dissociation tests (please refer to the water solubility and dissociation in sections 4.8 and 4.21 of IUCLID). Once the individual transformation products of the metal carboxylate become bioavailable (i.e. in the acidic environment in the gastric passage or after phagocytosis by pulmonary macrophages), the “overall” toxicity of the dissociated metal carboxylate can be described by a combination of the toxicity of these transformation products, i.e. the metal cation and carboxylate anion according to an additivity approach.

 

2-ethylhexanoic, zirconium salt is the zirconium metal salt of 2-ethylhexanoic acid, which readily dissociates to the corresponding zirconium cation and 2-ethylhexanoate anions. The zirconium cation and the 2-ethylhexanoate anion are considered to represent the overall toxicity of 2-ethylhexanoic, zirconium salt in a manner proportionate to the free acid and the metal (represented by one of its readily soluble salts). 

 

A detailed justification for the read-across approach is added as a separate document in section 13 of IUCLID.

 

Genetic toxicity

No genetic toxicity study with 2-ethylhexanoic acid, zirconium salt is available, thus the genetic toxicity will be addressed with existing data on the dissociation products as detailed in the table below.

 

Table: Summary of genetic toxicity data of 2-ethylhexanoic acid, zirconium salt and the individual constituents.

	Zirconium	2-ethylhexanoic acid (CAS# 149-57-5)	2-ethylhexanoic acid, zirconium salt (CAS# 22464-99-9)
In vitro gene mutation in bacteria	Negative	Negative	Negative (read-across)
In vitro cytogenicity in mammalian cells or in vitro micronucleus test	Negative	Negative	Negative (read-across)
In vitro gene mutation study in mammalian cells	Negative	Negative	Negative (read-across)

Zirconium

Bacterial reverse mutation assays performed according to OECD Guideline 471 with zirconium dioxide (Laus, 2008) and zirconium acetate (Scarcella, 2013). Both test items were not mutagenic with and without metabolic activation. In vitro mammalian chromosome aberration tests performed according to OECD Guideline 473 with zirconium dioxide (Notox, 2010) and zirconium acetate (Ciliutti, 2013). Both test items were neither mutagenic nor clastogenic with and without metabolic activation. In vitro mammalian cell gene mutation tests performed according to OECD Guideline 476 with zirconium dioxide (Notox, 2010) and zirconium acetate (Bisini, 2013). The test items were tested for mutation using L5178Y mouse lymphoma cells. Both test items were not mutagenic under the experimental conditions, with and without metabolic activation.

No reliable data were available on the genetic toxicity in vivo endpoint. Zirconium dioxide and zirconium acetate tested negative in in vitro toxicity tests (Ames test, mammalian chromosome aberration test, mouse lymphoma assay and comet assay) and therefore no in vivo mutagenicity tests should be performed for zirconium.

 

2-ethylhexanoic acid

2-ethylhexanoic acid was negative in the bacterial Ames test with S. typhimurium strains TA 98, TA 100, TA 1535 and TA 1537 and E. coli WP2 uvr A (Jung et al., 1982; Zeiger et al., 1988; Warren et al., 1982), as well as in a HPRT locus assay with mammalian CHO cells (Schulz et al., 2007). In cultured human lymphocytes, 2-ethylhexanoic acid induced a minimal increase in frequency of sister-chromatid exchanges (below 1.5 fold increase at concentrations of the test substance of 0.63 to 2.5 mM; Sipi et al., 1992), which is not considered significant.

In an in vivo micronucleus assay with mice, 2-ethylhexanoic acid was administered by gavage up to the maximum tolerated oral dose of 1600 mg/kg/day. No bone marrow toxicity was observed, nor did the test substance induce any bone marrow micronuclei (Holstrom et al., 1994).

 

2-ethylhexanoic acid, zirconium salt

2-ethylhexanoic acid, zirconium salt is not expected to be genotoxic, since the two constituents zirconium and 2-ethylhexanoic acid have not shown gene mutation potential in a range of in vitro test systems. Thus, 2-ethylhexanoic acid, zirconium salt is not classified according to regulation (EC) 1272/2008 as genetic toxicant. Further testing is not required. For further information on the toxicity of the individual constituents, please refer to the relevant sections in the IUCLID and CSR.

 

Justification for classification or non-classification

2-ethylhexanoic acid, zirconium salt is not expected to be genotoxic, since the two constituents zirconium and 2-ethylhexanoic acid have not shown gene mutation potential in a range of in vitro test systems. Thus, 2-ethylhexanoic acid, zirconium salt is not classified according to regulation (EC) 1272/2008 as genetic toxicant.