Untitled

Abstract

During the last few years, research on toxicologically relevant properties of engineered nanoparticles has increased tremendously. A number of international research projects and additional activities are ongoing in the EU and the US, nourishing the expectation that more relevant technical and toxicological data will be published. Their widespread use allows for potential exposure to engineered nanoparticles during the whole lifecycle of a variety of products. When looking at possible exposure routes for manufactured Nanoparticles, inhalation, dermal and oral exposure are the most obvious, depending on the type of product in which Nanoparticles are used. This review shows that (1) Nanoparticles can deposit in the respiratory tract after inhalation. For a number of nanoparticles, oxidative stress-related inflammatory reactions have been observed. Tumour-related effects have only been observed in rats, and might be related to overload conditions. There are also a few reports that indicate uptake of nanoparticles in the brain via the olfactory epithelium. Nanoparticle translocation into the systemic circulation may occur after inhalation but conflicting evidence is present on the extent of translocation. These findings urge the need for additional studies to further elucidate these findings and to characterize the physiological impact. (2) There is currently little evidence from skin penetration studies that dermal applications of metal oxide nanoparticles used in sunscreens lead to systemic exposure. However, the question has been raised whether the usual testing with healthy, intact skin will be sufficient. (3) Uptake of nanoparticles in the gastrointestinal tract after oral uptake is a known phenomenon, of which use is intentionally made in the design of food and pharmacological components. Finally, this review indicates that only few specific nanoparticles have been investigated in a limited number of test systems and extrapolation of this data to other materials is not possible. Air pollution studies have generated indirect evidence for the role of combustion derived nanoparticles (CDNP) in driving adverse health effects in susceptible groups. Experimental studies with some bulk nanoparticles (carbon black, titanium dioxide, iron oxides) that have been used for decades suggest various adverse effects. However, engineered nanomaterials with new chemical and physical properties are being produced constantly and the toxicity of these is unknown. Therefore, despite the existing database on nanoparticles, no blanket statements about human toxicity can be given at this time. In addition, limited ecotoxicological data for nanomaterials precludes a systematic assessment of the impact of Nanoparticles on ecosystems.

Heteroaggregation of nanoparticles with biocolloids and geocolloids

“…Nanomaterials are commonly defined as materials with at least one dimension below 100 nm [1]. There are three types of nanomaterials [2]: (1) nanofilms and coatings, which have one dimension less than 100 nm; (2) nanotubes, nanofibers and nanowires, which have two dimensions less than 100 nm; and (3) nanoparticles (NPs), which have three dimensions less than 100 nm [2,3].…”

“…The physico-chemical properties of nanoparticles are different with their bulk material due to the size effect. In fact, nanoparticles are regarded as a bridge between atomic or molecular structures and bulk materials [2], and quantum physics should be applied instead of classical physics for particles in the size range of 1-100 nm [1]. Nanoparticles have some special properties, typically including: (1) size effects (reducing the particles size can lead to the change of solubility, color, absorption or emission wavelength, and conductivity); (2) composition effects (different compositions of nanoparticles result in a different physical and chemical behavior); and (3) surface effects (the surface behavior of nanoparticles are changed by their dispersibility, conductivity and other related properties) [1].…”

“…Similar to colloidal particles, the fundamental science of surfaces and interfaces is very important for nanoparticles. In the nanoscale, more atoms are found at the surfaces, which makes the nanoparticles more reactive [1]. One case in point is that nanoparticles can quickly agglomerate into larger particles due to higher surface energy [1,[14][15][16].…”

“…It is very likely that the large amount of production of ENMs will lead to their release into the environment through production, application, and disposal processes [1,22,23]. For example, titanium dioxide nanoparticles (TiO 2 NPs) were modeled and predicted to be discharged to the wastewater treatment plant, landfill and other environments [4,17,24].…”

“…Most nanoparticles tend to aggregate once they are hydrated, and this aggregation process is important for their sedimentation rates [14][15][16]. The properties and implication of nanoparticles will be altered once they are agglomerated into larger particles and settle out of water column [1]. In most waters, including natural waters and tap water, heteroaggregation, or aggregation between different types of particles, will take place [44].…”