Occupational Exposure to Carbon Nanotubes and Carbon Nanofibres: More Than a Cobweb

Abstract

Carbon nanotubes (CNTs) and carbon nanofibers (CNFs) are erroneously considered as singular material entities. Instead, they should be regarded as a heterogeneous class of materials bearing different properties eliciting peculiar biological outcomes both in vitro and in vivo. Given the pace at which the industrial production of CNTs/CNFs is increasing, it is becoming of utmost importance to acquire comprehensive knowledge regarding their biological activity and their hazardous effects in humans. Animal studies carried out by inhalation showed that some CNTs/CNFs species can cause deleterious effects such as inflammation and lung tissue remodeling. Their physico-chemical properties, biological behavior and biopersistence make them similar to asbestos fibers. Human studies suggest some mild effects in workers handling CNT/CNF. However, owing to their cross-sectional design, researchers have been as yet unable to firmly demonstrate a causal relationship between such an exposure and the observed effects. Estimation of acceptable exposure levels should warrant a proper risk management. The aim of this review is to challenge the conception of CNTs/CNFs as a single, unified material entity and prompt the establishment of standardized hazard and exposure assessment methodologies able to properly feeding risk assessment and management frameworks.

Assessment of the toxicity and carcinogenicity of double-walled carbon nanotubes in the rat lung after intratracheal instillation: a two-year study

“…The very light weight of CNTs make them easily airborne and inhaled. Consequently, the possibility that CNTS may exhibit foreign body toxicity in the airways and pleura is of concern [2][3][4][5][6][7]: also see Hansen and Lennquist 2020 [8]. Harmful fibrous particles like asbestos are known to induce fibrosis and cancer through chronic unresolved inflammation characterized by inflammatory cell accumulation and production of reactive oxygen and nitrogen spices (ROS & RNS) that can damage DNA and through repeated cycles of tissue damage and repair fix potentially transforming mutations into daughter cells [9][10][11][12][13][14][15].…”

In vitrotoxicity of carbon nanotubes: a systematic review

“…Starting from 2007, the scientists' interest in the CNT bio-effects was fully switched to CNTs in a form of dispersion facilitated by the increased industrial production and humanity fears about the toxic effect on the environment and on employees involved in the synthesis of the materials. 89 Several years later, it was evident that being easily absorbed onto the skin surface, CNTs internalized through epithelial tissues forming barriers in a human organism ( Fig. 1 ).…”

“…The authors of the present review propose that such a shift could be due to the high rate of methods development to disperse CNTs and their possible impact in dispersion on the environment and human health by means of internalization through epithelial tissues. 89 …”

“…The authors of the present review propose that such a shi could be due to the high rate of methods development to disperse CNTs and their possible impact in dispersion on the environment and human health by means of internalization through epithelial tissues. 89 Furthermore, CNTs dispersed in liquids have wider application range than those placed onto the substrates or just in the form of thin lms because of greater probabilities for contact with cell membranes and internalization into cells. For instance, CNTs are rather promising as a substrate for orthopedic or implant application, tissue engineering, and as electrodes or conductive substrates for electrically active tissues.…”

Immunotoxicity of Carbon-Based Nanomaterials, Starring Phagocytes

“…A significant risk is associated with CNTs and carbon nanofibers (CNFs), which have repeatedly been shown to cause pulmonary toxicity via induction of chronic inflammation and fibrotization of lung tissue, as recently reviewed by Bergamaschi et al [ 49 ]. In 2014, the International Agency for Research on Cancer Working Group officially classified long rigid MWCNT-7 (manufactured by Mitsui, Japan) as a potential carcinogen (group 2B) [ 50 ].…”