Year: 2013
Type: report
Abstract: Carbon nanotubes (CNTs) can be seen as graphene sheets rolled to form cylinders.\nCNTs may be categorised as single- (SWCNT) or multi-walled (MWCNT). Due\nto the small size, the number of particles as well as the surface area per mass unit\nis extremely high.\nCNTs are highly diverse, differing with respect to e.g., diameter, length, chiral\nangles, chemical functionalisation, purity, stiffness and bulk density. Today, CNTs\nare utilised primarily for the reinforcement of composite polymers, but there is\nconsiderable potential for other applications. The rapidly growing production and\nuse of CNTs increases the risk for occupational exposure. Since CNTs in bulk\nform are of very low density and much dust is produced during their handling,\nexposure by inhalation appears to represent the greatest potential risk in the work\nplace. However, most work place measurements involved sampling periods that\nare too short, varying sampling techniques and non-specific analytical methods.\nCNTs may be absorbed via inhalation and ingestion. Systemic uptake via the\nskin has not been demonstrated.\nHuman toxicity data on CNTs are lacking and interpretation of animal studies\nis often problematic since the physical properties and chemical composition are\ndiverse, impurities may be present and data are sometimes omitted. Because of the\nphysical similarities between asbestos and CNTs, it can be suspected that the latter\nmay also cause lung fibrosis, mesothelioma and lung cancer following inhalation.\nIntraperitoneal and intrascrotal administration of CNTs causes mesothelioma in\nanimals, but no inhalation carcinogenicity studies have been conducted. Thus, it is\ntoo early conclude whether CNTs cause mesothelioma and lung cancer in humans.\nBoth SWCNTs and MWCNTs cause inflammation and fibrosis in the lungs of\nrelevant animal types and for MWCNTs these effects are also seen in the pleura.\nFor instance, minimal histiocytosis and mild granulomatous inflammation in the\nlungs and lung-draining lymph nodes have been observed in rats exposed for 13\nweeks to 0.1 mg/m3 MWCNTs (lowest observed adverse effect level, LOAEL),\nwith more pronounced inflammation in both mice and rats at higher doses. Thus,\ninflammatory responses in the lungs may be considered as the critical effect. However,\nthe LOAEL of CNTs should be interpreted cautiously, since their toxicity is\nlikely to vary widely, depending on the structure and physicochemical properties,\nas well as the contribution from non-carbon components. It is also uncertain which\ndose metric (e.g., mass, number or surface area per air volume unit) is most appropriate.\nSome studies indicate that longer straight CNTs evoke more pronounced\nbiological effects than shorter or tangled fibres.
Institution: Lund University
Language: Spanish
Subfield: Biomedical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W1808902591