Overview

Background

The technology of engineered nanoparticles is rapidly growing to become a major industry. Today, more than 1.000 nanoparticle-containing products are available on the global market. Since silver is well established as an antimicrobial agent, the use of engineered silver nanoparticles in textiles, cosmetics, pharmaceuticals and other commercial applications accounts for about 25 % of the overall nanoparticle-containing products. Thus, the use of all these products may result in a significant environmental exposure of silver nanoparticles, e.g. via wastewater streams and via abrasion of particles during use and disposal. Hence, the still limited data on the exposure, the behaviour, the fate and the effects of silver nanomaterials in various environmental compartments need to be completed.

 

Aims

The UMSICHT project addresses this deficient knowledge concerning fate, behaviour and effects of silver nanoparticles at different environmental conditions in order to avoid or minimize adverse environmental effects. The project is within the scope of an exemplary risk assessment provided by the REACh regulation.

The main aims and objectives of UMSICHT are:

1. The identification of a structure-activity relationship between specific characteristics of nanoparticles and their biological activity
   
   • Construction and characterization of silver nanoparticles with specific parameters
2. Analysis of the fate, the behaviour and the effects of silver originating from a consumer product
   
   • Analogue simulation of relevant exposure scenarios
   • Characterization of nanomaterial fate and behaviour under these scenarios
   • Characterization of environmental and biological effects
3. Hazard and risk assessment case study for nanomaterials
   
   • Exemplary hazard and risk assessment for specific idealized systems taking account of the variability of silver nanoparticles and silver containing products

 

Scientific activity

Within the UMSICHT project 16 partners form academia, industry and the regulative authorities are brought together to ensure with their special expertise and their skills a concerted research plan. The project focuses on basic research questions with regard to effects of silver nanoparticles as well as on realistic exposure scenarios, which are relevant for a prospective and safe implementation of particle technologies, and which help to solve regulatory problems. For these purposes silver nanoparticles of well defined characteristics as well as silver nanoparticle containing textiles will be analyzed and investigated. The methods for the detection of nanoparticles and their biological activity in different solutions and environmental compartments will be optimized or developed. The results will lead to a hazard and risk assessment as the final central feature of UMSICHT. The results from the basic research approach as well as the results from the realistic scenarios will finally be brought together in an exemplary hazard and risk assessment forming the key closing document of the UMSICHT project.

 

Intermediate Results (April 2012)

The following key statements representing the state-of-the-art of the UMSICHT project have been adopted by all participants on the last project meetings held at the BGR in Hannover from the 28 th to the 29 th of September 2011 as well as at DECHEMA on March 13, 2012. The statements are primarily based on the participants own research activities using carefully characterized silver nanoparticles as well as model textiles equipped with these particles. Additionally, the international state-of-the-art from recent literature has been integrated into the statements.

1. Principally, the handling and sample preparation of silver nanoparticles still needs the detailed development of proper methods and protocols. Even the seemingly simple and straight forward analysis of the total amount of silver species in samples containing different environmental matrices has to be further developed and optimized. Especially important here is the development of methods and techniques that allow for a differentiation between effects provoked by dissolved silver species and effects originating solely from the particulate state of silver.
   
   
2. It is not possible, and this holds true for all types of nanoparticles and nanomaterials, to derive general statements for the behaviour, fate and effects of silver nanomaterials. The reason for this is the fact that behaviour, fate and effects of nanoparticles (which can be produced in many different ways) are predominantly governed by the size, the shape, the coating and in case of metal-containing particles as well as by the oxidation state of a specific particle. This should be considered in particular with regard to reference materials.
   
   
3. Depending on the surrounding media each particle type behaves in a completely different way. Owing to this the most important factors are how strong the particles are bound to a carrier matrix (e.g. a textile) and the kinetics of the deliberation of silver ions from these particles as well as the fate of the released ions in different environments. The fate of silver ions (agglomeration, precipitation and adsorption to e.g. soils) strongly depends on the surrounding medium and its physico-chemical properties.
   
   
4. Owing to the still poorly understood agglomeration and sorption behaviour of silver nanomaterials the methods and guidelines describing the application of silver nanoparticles to test media and soil need to be further specified (e.g. according to storage conditions of stock solutions, application methods, preparation of dilution series, washing and cleaning of reusable lab ware).
   
   
5. For regulatory purposes a pragmatic and key parameter-oriented testing strategy seems to be the only way to handle the huge variety of particles. Such key parameters for metal-containing nanoparticles are e.g. size, zeta potential, surface functionality, oxidation state and ion deliberation kinetics.
   
   
6. Since the reaction kinetics of silver nanoparticles differ fundamentally from those of non-particulate silver species, studies investigating the chronic and long term effects of silver nanoparticles should be intensified. Such efforts should comprise long term and aging studies under realistic conditions as well as endpoints like bioaccumulation, biomagnification and molting over long time frames, which are so far not addressed by standard testing protocols.
   
   
7. There are many different technologies to equip textiles with silver nanoparticles. Depending on the textile matrix and the method used it can be difficult to reproducibly equip textiles with silver nanoparticles, especially if very high particle concentrations have to be handled.
   
   
8. Corresponding to the manifold methods and techniques to equip textiles with silver nanoparticles the resulting antimicrobial activity of these textiles can be highly variable ranging from very strong effects to nearly no influence on the growth of bacteria and fungi.
   
   
9. Precise analytics are essential – the low recovery rate of OECD–reference particles (NM-300K) might bias the toxicological assessment of Ag-NP in general.
   
   
10. NM-300K is highly mobile compared to AgNO₃ in most of the tested soils. Hence, this reference standard qualified for mobility studies in soils.
    
    
11. TiO₂-supported Ag-NP synthesised using flame spray pyrolysis have a bactericidal effect on textile fibres, but TiO₂–NP have the same bactericidal effect on their own.