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
 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.
Nanomaterials appear to have toxicity effects that are unusual and not seen with larger particles, and these smaller particles can pose more of a threat to the human body
due to their ability to move with a much higher level of freedom while the body is designed to attack larger particles rather than those of the nanoscale.
 Titanium dioxide (TiO2) dust is considered a lung tumor risk, with ultrafine (nanoscale) particles having an increased mass-based potency relative to fine TiO2, through
a secondary genotoxicity mechanism that is not specific to TiO2 but primarily related to particle size and surface area.
Other properties of nanomaterials that influence toxicity include: chemical composition, shape, surface structure, surface charge, aggregation and solubility, and the
presence or absence of functional groups of other chemicals.
Although the extent to which animal data may predict clinically significant lung effects in workers is not known, the toxicity seen in the short-term animal studies indicate
a need for protective action for workers exposed to these nanomaterials.
In addition, many nanoparticles will agglomerate to some extent in the environment or in the body before they reach their target, so it is desirable to study how toxicity
is affected by agglomeration.
 Mechanisms of toxicity Oxidative stress 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.
 Carbon-based Main article: Toxicology of carbon nanomaterials The latest toxicology studies on mice as of 2013 involving exposure to carbon nanotubes (CNT) showed
a limited pulmonary inflammatory potential of MWCNT at levels corresponding to the average inhalable elemental carbon concentrations observed in U.S.-based CNT facilities.
The large number of variables influencing toxicity means that it is difficult to generalise about health risks associated with exposure to nanomaterials – each new nanomaterial
must be assessed individually and all material properties must be taken into account.
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.
Size can also affect the particles’ reactivity and the specific mechanism by which they are toxic.
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.
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.
In principle, a large number of particles could overload the body’s phagocytes, cells that ingest and destroy foreign matter, thereby triggering stress reactions that lead
to inflammation and weaken the body’s defense against other pathogens.
 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.
 Dermal Some studies suggest that nanomaterials could potentially enter the body through intact skin during occupational exposure.
 Because of quantum size effects and large surface area to volume ratio, nanomaterials have unique properties compared with their larger counterparts that affect their
Because nanotechnology is a recent development, the health and safety effects of exposures to nanomaterials, and what levels of exposure may be acceptable, is not yet fully
 Gastrointestinal Ingestion can occur from unintentional hand-to-mouth transfer of materials; this has been found to happen with traditional materials, and it is
scientifically reasonable to assume that it also could happen during handling of nanomaterials.
Surface chemistry and charge NPs, in their implementation, are covered with coatings and sometimes given positive or negative charges depending upon the intended function.
Unfortunately, agglomeration has frequently been ignored in nanotoxicity studies, even though agglomeration would be expected to affect nanotoxicity since it changes the size,
surface area, and sedimentation properties of the nanoparticles.
 One study considers release of airborne engineered nanoparticles at workplaces, and associated worker exposure from various production and handling activities, to
be very probable.
 Nanomaterials can be toxic to human tissue and cell cultures (resulting in increased oxidative stress, inflammatory cytokine production and cell death) depending on their
composition and concentration.
 The inhalation risk is affected by the dustiness of the material, the tendency of particles to become airborne in response to a stimulus.
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.
 Biodistribution The extremely small size of nanomaterials also means that they much more readily gain entry into the human body than larger sized particles.
The greater chemical reactivity of nanomaterials can result in increased production of reactive oxygen species (ROS), including free radicals.
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.
As is the case for toxicity profile with any chemical modification of a structural moiety, the authors suggest that individual molecules be assessed individually.
Nanotoxicological studies are intended to determine whether and to what extent these properties may pose a threat to the environment and to human beings.
No reports of actual adverse health effects in workers using or producing these nanomaterials were known as of 2013.
For example, particles of different sizes can deposit in different places in the lungs, and are cleared from the lungs at different rates.
 Animal studies indicate that carbon nanotubes and carbon nanofibers can cause pulmonary effects including inflammation, granulomas, and pulmonary fibrosis, which were
of similar or greater potency when compared with other known fibrogenic materials such as silica, asbestos, and ultrafine carbon black.
Above all, these properties would have to be determined not only on the nanocomponent before its introduction in the living environment but also in the (mostly aqueous) biological
When diluted, the positively charged metal ions often experience an electrostatic attraction to the cell membrane of nearby cells, covering the membrane and preventing it
from permeating the necessary fuels and wastes.
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Photo credit: https://www.flickr.com/photos/44949218@N02/9446982168/’]