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EC number: 231-131-3
CAS number: 7440-22-4
Range finding for intradermal induction: Three animals were intradermal
treated with 100%, 30%, 10% and 3% concentrations of the test substance.
Scores were obtained 24 hours after application. Slight to moderate
irritation was observed in all concentrations tested. From the 30%
concentration upward necrosis was observed as well. No irritation was
observed after topical induction with 30% and 100% test substance
concentrations in three animals. Challenge: No skin reactions were
observed in test or control animals following the challenge application
in the main study after 24 hours.
The hazard assessment for nanosilver is determined by the extent by which silver ions are released (as determined by in-vivo toxicokinetic data). In this respect, the key data for the hazard assessment of nanosilver is restricted to studies using nanosilver as test item.
The data used for the human health hazard assessment of nanosilver (‘target substances’) are not restricted to studies referring to only these substances as test item. Instead, a more generic approach for the toxicological assessment of “silver” in general is adopted by also including information/data generated with other inorganic silver substances (like silver nitrate or silver sulphate) or organic silver salts (such as silver acetate) that have the potential to release silver ions (‘source substances’) as supporting evidence.The basic assumption for this is that the systemic toxicity is driven by the released silver ions (Ag+), which is considered the primary relevant species of silver for the hazard assessment. It is noted that many silver substances have a low to negligeable water solubility and are considered of low bioavailability in the body. Once dissolved, the counter-ions released from the silver salt (such as chloride or sulphate anions) are not considered further in the hazard assessment, since these are typically either ubiquitous ions in a physiological environment (like chloride) or generally known to be of no relevant toxicological (systemic) concern (like acetate or sulphate). Note that a different approach is applied if a substance is causing local effects, such as the soluble and corrosive silver nitrate. The read-across approach is used maximally to avoid unnecessary animal testing.
The approach and justification for the applied human health hazard assessment is detailed in the read-across justification document attached to the silver IUCLID file in section 13. The various human health endpoints of the silver REACH dossiers have been updated on an individual basis to reflect the approach that is described in the read-across justification document.
Based on a weight-of-evidence assessment, it is concluded that silver substances do not elicit skin sensitising effects:
Long term industrial experience does not raise any concern on skin sensitisation attributable to silver substances (personal communication, members of the Silver Work Group of the Precious Metals and Rhenium Consortium, 2010-07-27). Furthermore, a literature search has been conducted to check whether published literature is available which would provide further information on the potential occurrence or absence of skin sensitisation effects of silver substances, specifically in occupational settings. A report on this literature search is attached to the endpoint summary on sensitisation in the technical dossier. As a result, only a limited number of case reports dealing with skin sensitisation could initially be identified. However, upon close inspection, in several of these silver was not the potential cause. For example, one study investigated skin effects in workers with a range of precious metal compounds and found that silver compounds were not causing allergic skin reactions (Bruevich et al 1980). In other cases, “silver” was mentioned but not in the context of sensitisation by silver, but e. g. where thiourea contained in a silver polish was identified as a sensitiser (Dooms-Goossens, 1988).
Overall, very few publications are available and no specific concern for sensitising properties of silver (compounds) could be identified based on human data.
Two reliable studies on standard skin sensitisation tests are available with silver containing products/preparations:
Moore, G.E. (1999): Dermal sensitisation study (Buehler Method) in guinea pigs, with a biocidal product (aqueous solution) containing 2438 ppm Ag+ ions, besides other ingredients.
Prinsen, M.K. (1995): Sensitization study in guinea pigs (maximization test) with a liquid plant preservative preparation containing 18 g/L of silver thiosulfate in aqueous solution, besides other ingredients.
As a third source of information, the data published by Kim et al. (2012) on a guinea pig maximisation test are presented. Kim et al. studied the sensitising properties of a nano-silver product (in 1% citrate solution) in close agreement with OECD TG 406. Whereas this publication is of limited reliability since no test concentrations are stated and the use of a positive control is not reported, the clear negative outcome (no skin sensitisation) is in agreement with other information.
Neither human nor animal data show any specific concern for skin sensitising properties of silver or silver substances. Based on a weight-of-evidence assessment it is concluded that classification for skin sensitisation is not required and that further experimental verification is not justified.
Migrated from Short description of key information: Neither human nor animal data show any specific concern for skin sensitising properties of silver or silver substances. Based on this weight-of-evidence assessment, it is concluded that classification for skin sensitisation is not required and that further experimental verification is not justified (see discussion). Justification for selection of skin sensitisation endpoint: Weight-of-evidence assessment based on human and animal data.
Neither human nor animal data show any
specific concern for skin sensitising properties of silver or silver
substances. Based on this weight-of-evidence assessment, it is concluded
that classification for skin sensitisation is not required and that
further experimental verification is not justified. In consequence,
classification for skin sensitisation is not required for silver
Similarly, based on a complete absence of any
indication of respiratory sensitisation in the public domain,
classification is not required.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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