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Introductionto read-across matrix

A comprehensive data gap analysis was conducted for the entire substance portfolio of the Metal carboxylates REACH Consortium (MCRC), covering 10 metal carboxylates in total. This literature screening effort included:

 

  • all available proprietary studies from the Metal carboxylates REACH Consortium (MCRC)
  • detailed literature searches in online databases
  • screening of human health review articles
  • rigorous quality and reliability screening according to Klimisch criteria, where those criteria apply

 

During the literature search and data gap analysis it became obvious that the overall database on substance-specific human health hazard data for the metal carboxylates is too scant to cover all REACH endpoints. Therefore, the remaining data gaps had to be covered by either experimental testing or read-across from similar substances.

 

Selected endpoints for the human health hazard assessment are addressed by read-across, using a combination of data on the organic acid counterion and the metal (or one of its readily soluble salts). This way forward is acceptable, since metal carboxylates 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 tests (please refer to the water solubility data in section of the IUCLID and chapter of the CSR). Once the individual constituents 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 the toxicity of the “individual” constituents. Since synergistic effects are not expected for this group of metal carboxylates, the human health hazard assessment consists of an individual assessment of the metal cation and the organic anion.

 

The hazard information of the individual constituents was obtained from existing REACH registration dossiers via a license-to-use obtained by the lead registrant. These registration dossiers were submitted to ECHA in 2010 as full registration dossiers, and are thus considered to contain relevant and reliable information for all human health endpoints. All lead-registrant dossiers were checked for completeness and accepted by ECHA, i.e. a registration number was assigned.

 

Zinc neodecanoate is the zinc metal salt of neodecanoic acid, which readily dissociates to the corresponding divalent zinc cation and neodecanoic acid anions. The zinc cation and the neodecanoic acid anion are considered to represent the overall toxicity of the zinc neodecanoate in a manner proportionate to the free acid and the metal (represented by one of its readily soluble salts). Based on the above information, unrestricted read-across is considered feasible and justified.

 

Introduction to the neoacids hazard assessment

The carboxylic acids “neodecanoic acid” and “fatty acid C9 to C13 neo” are considered similar in their toxicological profile and are therefore grouped together. Both neoacids originate from the same production process in which a branched olefin is reacted with carbon monoxide and water at elevated temperature and pressure in th1e presence of an acid as catalytic component. The dossiers for neodecanoic acid and fatty acid C9 to C13 neo contain human health hazard information on both substances indicating that the toxicological profile is similar. This approach was also used and accepted in the US EPA HPV programme, even for a wider range of neo-acid substances (US EPA, April 2009: http://www.epa.gov/chemrtk/pubs/summaries/neoc528/c13335tc.htm).

Based on the above information “neodecanoic acid” and “fatty acid C9 to C13 neo” will be assessed for their hazardous properties, using the same dataset for both substances.

 

Although the term „constituent“ within the REACH context is defined as substance (also being part of a mixture), the term constituent within this hazard assessment is meant to describe either part of the metal carboxylate salt, i.e. anion or cation.

Genetic toxicity

No genetic toxicity study with zinc neodecanoate 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 the zinc neodecanoate and the individual constituents.

 

(slightly soluble) zinc substances

Neodecanoic acid
(CAS# 26896-20-8)

Zinc neodecanoate
(CAS# 27253-29-8)

In vitro gene mutation in bacteria

negative

(weight of evidence)

negative

negative
(read-across)

In vitro cytogenicity in mammalian cells or in vitro micronucleus test

negative

negative
(read-across)

In vitro gene mutation study in mammalian cells

no data

negative
(read-across)

In vivo cytogenicity

no data

negative
(read-across)

 

Zinc

The overall weight of the evidence from the existing in vitro and in vivo genotoxicity assays suggests that zinc compounds do not have biologically relevant genotoxic activity. This conclusion is in line with those achieved by other regulatory reviews of the genotoxicity of zinc compounds (WHO, 2001; SCF, 2003; EU RAR, 2008, MAK, 2009). Hence, no classification and labelling for mutagenicity is required.

 

Neodecanoic acid

Neodecanoic acid is not mutagenic in vitro in bacterial mutation assays (with and without metabolic activation) and was not clastogenic in a cytogenetic assay. Although a test on in vitro gene mutation in mammalian cells is not provided, the bacterial reverse mutation test covering the same endpoint did not show any sign of mutagenic potential with an without metabolic activation. This data suggests that neodecanoic acid is not genotoxic in vitro and likely not genotoxic in vivo.

 

Zinc neodecanoate

Zinc neodecanoate is not expected to be genotoxic, since the two constituents zinc and neodecanoic acid have not shown a genotoxic potential in a range of in vitro test systems. Thus, zinc neodecanoate is not to be 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 selection of genetic toxicity endpoint
Read-across information.

Short description of key information:
Zinc neodecanoate is not expected to be genotoxic.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

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

Furthermore, zinc neodecanoate has not to be classified according toDirective 67/548 EC as genetic toxicant.