Nanoparticles are employed in a variety of products in different forms and functions. In the course of this study, the following materials were chosen:
Nanosilver – currently the most used nanoparticle
Titanium dioxide – used in a variety of products
Carbon Black – has been used for a long time in many products
Cerium oxide – naturally occurring from burning processes.
For every material a commercially available product was chosen (in accordance) for which a release of nanoparticles in the course of its life cycle can be expected.
Nanosilver – Wiping cloth
Titanium dioxide – Wall paint
Carbon Black – Bulking agent in tires
Cerium oxide – Additives in Fuel (Diesel).
Emission of nano-objects and nano-structured material from products depends on different factors (e.g. type, shape, function, application). When nano-objects are released from products, they usually don't exist as loose nano-objects, rather, they could be embedded in a matrix, could be functionalized or coated which in turn affects their properties. When the particles are released in the environment, they are also exposed to various abiotic and biotic factors which could affect their properties. The release and the behaviour of particles in the environment could therefore differ greatly from product to product and also depending on the abiotic and biotic factors they are exposed to. With the current state of knowledge, no particular substance groups or mechanisms for release, transportation and retention in the environment can therefore be formed.
There are several studies which give indications about the processes concerning the properties and retention of nanoscale particles in air. There are also initial studies which give some indications about the properties and retention of nano-objects in water and soils. These are however difficult to quantify with the current state of measurement techniques.
This heterogeneous picture of the release and transport of particles is also shown for the substances and products examined in this study. The main release paths in the course of the life cycle occurs in air or water, whereby nanoscale TiO2 and silver are most probably released primarily in water while carbon black and cerium oxide are released primarily in air.
A direct exposure to humans and animals can occur through the skin, orally or through respiration. Dermal exposure however plays a minor role for humans. It is unclear how relevant the dermal exposure is for other organisms. A direct oral uptake seems unlikely for adults. The relevance of an indirect uptake through foodstuffs still needs to be studied. For other organisms, particularly aquatic organisms, there seems to be more relevance in oral uptake.
The respiratory intake is seen by many scientists as the most important uptake pathway in humans. In the products considered in this study, model estimates show that the environmental concentration of the examined nano-objects is currently not critical, whereby it is expected that in future the concentration of substances such as nanoscale TiO2 can reach critical levels. There are knowledge gaps in the area of exposure concentrations especially concerning possible bioaccumulation of nanoscale materials.
Generally, the reference study presented here shows that the current state of knowledge in the area of release, transportation, retention and exposure of nano-objects to humans relies on a few studies. The current knowledge is insufficient for making any generalised statements which are relevant for risk assessment. For some cases no easy applicable techniques (e.g. detection of nanoparticles in soils), standards (e.g. quantification of release scenarios), process information (e.g. agglomeration / deagglomeration) are available allowing to derive the necessary broader understanding.
From the results of the study, the following research needs and need for action arise:
Quantitative examination of the release of particles from products during their life cycles, including the characterization of the shape / functionalisation where the nano-objects / nano-materials are release, for different and also standardised conditions.
Qualitative and quantitative examination of the interaction of nano-materials with water and soils
Linking of the experimental examinations with the modelling of the release, proliferation/mobility and expected environmental concentration
Development of measurement techniques specifically for nano-objects in aquatic media, sediments and soils.
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