Abstract
In light of the broad spectrum of products containing nanosilver, the harmfulness of nanosilver to human health and the environment was intensively discussed at a conference held in February 2012 at the BfR. The conference agenda covered the aspects of analytics of nanosilver materials, human exposure and toxicology as well as effects on microorganisms and the environment. The discussion recovered major gaps related to commonly agreed guidelines for sample preparation and central analytical techniques. In particular, the characterization of the nanoparticles in complex matrices was regarded as a challenge which might become a pitfall for further innovation and application. Historical and anecdotal records of colloidal silver have been sometimes taken as empirical proof for the general low toxicity of nanosilver. Yet as reported herein, a growing number of animal studies following modern performance standards of toxicity testing have been carried out recently revealing well-characterized adverse effects on different routes of exposure in addition to argyria. Furthermore, recent approaches in exposure assessment were reported. However, consumer exposure scenarios are only starting to be developed and reliable exposure data are still rare. It was further widely agreed on the workshop that the use of silver may lead to the selection of silver resistant bacteria. With respect to its environmental behavior, it was suggested that nanosilver released to wastewater may have negligible ecotoxicological effects. Finally, the presentations and discussion on risk assessment and regulation of nanosilver applications gave insights into different approaches of risk assessment of nanomaterials to be performed under the various regulatory frameworks.
Highlights
The recent recommendation of the European Commission on the definition of nanomaterials is emphasizing the determination of the non-bound particles as a number size distribution from 1 to 100 nm (EU Commission 2011)
At JRC, the following techniques are used for in-depth analyses of the properties of nanoparticles at the molecular level: X-ray photoelectron spectroscopy (XPS) to characterize the surface chemistry of the nanoparticles; synchrotron radiation circular dichroism (CD) to study the various alterations of the protein corona that would occur during interaction of the particles (Laera et al 2011) and nuclear magnetic resonance (NMR) spectroscopy to monitor any changes which can occur in the conformation of ligands
An consumable amount of 100 ml would result in an acute oral exposure to 4.2 μg of silver. While this seems low in comparison to reported silver concentrations in US drinking water in the 60s and 70s of the last century, von Götz reasoned that a comparison to apparently safe water levels could be foiled by the circumstance that a small fraction of the released silver might consist of nanoparticles
Summary
State of the art in human risk assessment of silver compounds in consumer products: a conference report on silver and nanosilver held at the BfR in 2012. Bernd Schäfer · Jochen vom Brocke · Astrid Epp · Mario Götz · Frank Herzberg · Carsten Kneuer · Yasmin Sommer · Jutta Tentschert · Matthias Noll · Isabel Günther · Ursula Banasiak · Gaby‐Fleur Böl · Alfonso Lampen · Andreas Luch · Andreas Hensel
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