Potential health risks and safety concerns of nanomaterials
Much is already known about potential health effects related to exposure to nanomaterials, but insight comprehensive view of all nanomaterials is missing. At present, poorly soluble nanoparticles are our main concern. Their extremely small size increases the risk that they enter the body via the airways, the gastrointestinal tract and the skin.
The discussion on nanomaterial safety is the focus of this particular section. Nanoparticles are known to be associated with health issues, especially the single nanoparticles (un-agglomerated, un-aggregated). Therefore, implementation of the definition of nanomaterials in regulations and guidelines to restrict health risks is necessary (see Bleeker et al. 2013). Materials within the definition clearly contain nanomaterials, but materials outside the definition might also contain free nanoparticles (with potentially related health issues).
Little is known about the health issues directly related to bodily uptake but knowledge has shown that the amount of particles taken up, the frequency of exposure, the properties of the particles and the targeted organs and tissues are important. Smaller particles have a bigger surface area to mass ratio than larger-sized particles, which can increase the reactivity and the potential to release ions. The increased reactivity may induce cells to produce large quantities of molecules such as oxygen radicals and inflammation messengers, leading to tissue damage and disturbance of the normal functioning of the body.
Cause of health impact remains unknown
At present it is unknown which nanomaterials can induce what kind of negative impact on health.
Lists with safe and non-safe nanomaterials do not exist. Health risks may be related especially to insoluble, long and stiff fibre- and sheet-shaped materials and nanoparticles of which the bulk material is classified as carcinogenic, mutagenic, sensitizing and/or reprotoxic (Cornelissen et al., 2011). However, experimental data on safety and epidemiological studies into the health risks are lacking.
The behaviour and toxicity of nanomaterials depend on their characteristics, including chemical composition, particle size, particle morphology, electrical charge, surface properties, and functional groups (if present). The particle diversity is such that it is impossible to fully test each and every particle type, thus research focuses on relationships between characteristics and toxicity in general, rather than on actually testing each individual type of particles.