CNT, Graphene & carbon black
Carbon nanotubes (CNT) are about 100 times stronger than steel of the same diameter, which means that strength can be added to materials without adding much weight. Carbon nanotubes are also elastic, lightweight and highly conductive. These properties (and their long length) make the material ideal for use in many industries like plastics, batteries, electronics, 3D printing, construction and diagnostics.
Unfortunately, their shape makes them easily respirable and many studies have shown they can have a variety of negative effects on human health. Most of the ill effects occur in the lungs, but there are hazards to other organs, too, including the brain, liver and heart. The International Agency for Research on Cancer (IARC) has designated one type of MWCNT (MWCNT-7) as “possibly carcinogenic to humans (Group 2B).” Due to the lack of evidence it is not possible to generalize the toxicity among the many different types of CNTs.
Boron Nitride BN
Boron nitride nanotubes (BNNT) were discovered in 1995 and show similar high tensile strength values as CNTs. They are also as thermally conductive as CNTs but electrically insulating. These rare properties make them very interesting materials for all kinds of applications involving thermal management and insulation.
Their excellent chemical stability and high tensile strength make them an ideal reinforcement material for polymers or aluminum.
The toxicity of BNNT is still mostly unknown. Initial in vitro and in vivo studies showed an induced dose-dependent increase in cytotoxicity and oxidative stress in human monocytic cells.
Silica (silicon dioxide) SiO2
The different forms of natural crystalline silica appear in nature in large quantities in rock, sand and clay. A large percentage of the earth’s crust contains silica.
Many activities in mining, construction or quarries result in the release of respirable crystalline silica particles.
It has long been known that inhaled RCS particles cause scar tissue inside the lung, reducing the gas transfer to and from the blood. This can result in chronic bronchitis or an irreversible, deadly silicosis.
Cellulose nanocrystals (CNC) and cellulose nanofibers (CNF) are refined from wood. Their renewable nature and their unique properties make them interesting materials for a wide range of applications.
The high tensile strength and good biocompatibility make it suitable for many applications ranging from paper, food and sanitary products to all kinds of reinforcement and filler materials.
Although nanocellulose is touted as a “bionanomaterial,” CNC in a dry frozen state is particularly respirable, which makes it a potential health hazard. Although some older studies have seemed to disprove the harmful effects of nanocellulose, some newer research has shown potentially adverse effects.
Titanium dioxide is used in paints, plastics, pharmaceuticals, food and cosmetics. Almost anything white is likely to contain titanium dioxide. It is known for its brightness, opacity and ability to block ultraviolet rays. TiO2 has been used as an additive in many products in many industries for so long that it is considered a safe material.
The use of nanoscale titanium dioxide, sometimes called ultrafine-grade titanium dioxide, warrants caution, as there is concern about the effects of inhaling dust during manufacturing and processing. Its small size makes employees at production facilities particularly vulnerable to respirable airborne particles.