Safety of nano silver in consumer products: many questions remain open
In its opinion on toxicity aspects of nano silver, the Federal Institute for Risk Assessment (BfR) had recommended to waive the use of nano silver in foods and articles of daily use until the data situation allows for a final assessment of the health risks. Mainly industry objected to this assessment by BfR that enough data were available for the evaluation of the health risks of nano silver in consumer products and foods. For that reason BfR had invited experts from research and science as well as representatives of associations and industry to a workshop in order to discuss existing risks and possible options for a comprehensive consumer protection. "The discussion confirmed the words of caution of BfR", said BfR President Professor Dr. Dr. Andreas Hensel, "because the situation continues to be characterised by the fact that not enough secured scientific findings about the specific effects of nano-sized silver particles are available."
Metallic silver and different silver compounds are used, for instance, in cosmetic agents as well as in different consumer products, mainly because of their anti-microbial effect. For textiles not only medical/therapeutic applications but increasingly also hygiene aspects play a role. The anti-microbial finishing of textile fibres is mainly to act against odour formation as a result of the microbial decomposition of sweat. In the meantime nano-sized silver particles are increasingly being used. Nano particles are particles with a diameter of less than 100 nanometres.
In its Opinion No. 24/2010 BfR pointed out that for silver particles in the nanoscale (nano silver) there might be an toxicological effect profile with additional toxic effects which have not yet been described for silver so far. Because of the special physicochemical properties of the nano particle form, a different toxicological effect potential is known for many nano materials. The BfR workshop has shown that for nanoscale silver only a few toxicological data are available so far, which have examined the material taking into account nano-specific aspects. Furthermore, the characterisation, both for the particles used and for the dosage, was only insufficient over many years, because amongst other things the corresponding analytical methods were not available. Many older studies on colloidal silver, which is at present often considered as nano material, do not meet the standards of modern toxicology. More recent studies resulted in clear indications of effects so far not yet known for silver. This includes pathological changes of tissues in the liver after oral and inhalative administration as well as in the lung after inhalative exposure, changes in physiological parameters of specific organs and a higher potency.
There are only a few regulatory provisions which define demands on the type and scope of toxicological data for the ingredients of certain products which have to be submitted for a health assessment prior to the placement on the market and/or continuation of marketing. Biocide products based on silver will be examined in future within the framework of an authorisation procedure. For the corresponding health assessment, applicants must submit the corresponding toxicological data. For consumer products such as textiles there is, however, no duty of notification or authorisation. Since industry is not obliged to provide the public authorities with toxicological data for an assessment, these are often lacking so that the health risk of nano silver containing products cannot or only difficulty be assessed. As a rule, information concerning the release of nano silver particles from textiles and products is only rarely available. Furthermore, the data situation concerning possible impacts on the threat of resistances against silver or antibiotics in a specific application context is insufficient. The uptake in the body is likewise not yet sufficiently clarified. Details about the uptake through the respiratory tract (lung, bronchial tube) and the distribution of the absorbed particles in the body (toxicokinetics) after inhalation are hardly known. Moreover there is a lack of data on the effect on skin (sensitisation potential, irritation effect) but also on reproduction toxicity, chronic toxicity and carcinogenic potential.
Articles of daily use and consumer products may not constitute any health risk based on statutory provisions during proper use or foreseeable misuse. Since no final safety assessment for man and the environment is available so far for nanoscale forms of silver due to the missing data, BfR continues to advise against a broad use of nano silver in consumer products.
The Federal Institute for Risk Assessment (BfR) is a scientific institution within the portfolio of the Federal Ministry of Food, Agriculture and Consumer Protection (BMELV). It advises the Federal Government and Federal Laender on questions of food, chemical and product safety. BfR engages in own research on topics that are closely linked to its assessment tasks.