Up to now, carbon nanotubes (CNTs) are not added to food or cosmetic products. Therefore, the uptake of CNTs via the lung, e.g. at the workplace during production, is the most likely entry path of CNTs into the body. Studies on laboratory animals have shown that carbon nanotubes can size-dependently penetrate into the deeper lungs regions. From there they are either removed by natural clearance processes or they can enter the body through the thin epithelial layer of the pulmonary alveoli.
Exposure of nanoparticles to the skin is mostly related to cosmetics or pharmaceutical products, e.g. sunscreens. Usage of carbon nanotubes in comparable applications is not planned. Therefore, direct contact with the skin is currently unlikely and restricted to possible accidents or improper use.
At present, carbon nanotubes (CNTs) are not used in food. Only in theory, they can be transported into the gastrointestinal tract through unwanted hand-to-mouth transfer or through swallowing of particles after their clearing process from the respiratory tract. As a rule, particles that have been taken up via the food are excreted via the faeces. Until now, there is no evidence for carbon nanotubes to
The term "carbon nanotubes" (CNTs) comprises a group of carbon-containing nanomaterials with diverse properties, which for example differ in their surface structure or in the number of walls. These features significantly affect the strength of the toxic effects of the CNTs. Many of the observed effects are due to the fibre-like form of the carbon nanotubes, which may cause indirect effects upon contact with the surface of the environmental organisms. Universally valid statements about the environmental toxicity of carbon nanotubes are not yet possible.