Nanotoxicology
[1] Because of quantum size effects and large surface area to volume ratio, nanomaterials have unique properties compared with their larger counterparts that affect their toxicity.
Of the possible hazards, inhalation exposure appears to present the most concern, with animal studies showing pulmonary effects such as inflammation, fibrosis, and carcinogenicity for some nanomaterials.
[5] Nanoparticles have much larger surface area to unit mass ratios which in some cases may lead to greater pro-inflammatory effects in, for example, lung tissue.
[6][7][8] One study considers release of airborne engineered nanoparticles at workplaces, and associated worker exposure from various production and handling activities, to be very probable.
[12] Biomedically, these antibacterial NPs have been utilized in drug delivery systems to access areas previously inaccessible to conventional medicine.
With the recent increase in interest and development of nanotechnology, many studies have been performed to assess whether the unique characteristics of these NPs, namely their large surface area to volume ratio, might negatively impact the environment upon which they were introduced.
The agglomeration/deagglomeration (mechanical stability) potentials of airborne engineered nanoparticle clusters also have significant influences on their size distribution profiles at the end-point of their environmental transport routes.
Dust generation is affected by the particle shape, size, bulk density, and inherent electrostatic forces, and whether the nanomaterial is a dry powder or incorporated into a slurry or liquid suspension.
Factors such as size, shape, water solubility, and surface coating directly affect a nanoparticle's potential to penetrate the skin.
At this time, it is not fully known whether skin penetration of nanoparticles would result in adverse effects in animal models, although topical application of raw SWCNT to nude mice has been shown to cause dermal irritation, and in vitro studies using primary or cultured human skin cells have shown that carbon nanotubes can enter cells and cause release of pro-inflammatory cytokines, oxidative stress, and decreased viability.
Ingestion may also accompany inhalation exposure because particles that are cleared from the respiratory tract via the mucociliary escalator may be swallowed.
In addition to questions about what happens if non-degradable or slowly degradable nanoparticles accumulate in bodily organs, another concern is their potential interaction or interference with biological processes inside the body.
[6] For some types of particles, the smaller they are, the greater their surface area to volume ratio and the higher their chemical reactivity and biological activity.
ROS and free radical production is one of the primary mechanisms of nanoparticle toxicity; it may result in oxidative stress, inflammation, and consequent damage to proteins, membranes and DNA.
[11] For example, the application of nanoparticle metal oxide with magnetic fields that modulate ROS leading to enhanced tumor growth.
[24] The properties of a nanomaterial such as size distribution and agglomeration state can change as a material is prepared and used in toxicology studies, making it important to measure them at different points in the experiment.
Further nanotoxicology studies will require precise characterisation of the specificities of a given nano-element: size, chemical composition, detailed shape, level of aggregation, combination with other vectors, etc.
There is a need for new methodologies to quickly assess the presence and reactivity of nanoparticles in commercial, environmental, and biological samples since current detection techniques require expensive and complex analytical instrumentation.
[26] Stakeholders concerned by the lack of a regulatory framework to assess and control risks associated with the release of nanoparticles and nanotubes have drawn parallels with bovine spongiform encephalopathy (‘mad cow's disease'), thalidomide, genetically modified food, nuclear energy, reproductive technologies, biotechnology, and asbestosis.
In light of such concerns, the Canadian-based ETC Group have called for a moratorium on nano-related research until comprehensive regulatory frameworks are developed that will ensure workplace safety.
