Health impact of fullerenes

The health impact of fullerenes involves the nanotoxicology of fullerenes such as buckyballs and carbon nanotubes.

Buckyballs

A review of works on fullerene toxicity by Lalwani et al. found little evidence that C60 is toxic.[1] The toxicity of these carbon nanoparticles varies with dose, duration, type (e.g., C60, C70, M@C60, M@C82, functional groups used to water-solubilize these nanoparticles (e.g., OH, COOH), and method of administration (e.g., intravenous, intraperitoneal). The authors recommended that the pharmacology of each fullerene- or metallofullerene-based complex be assessed as a different compound.

Moussa et al. (1996–97)[2] studied the in vivo toxicity of C60 after intra-peritoneal administration of large doses. No evidence of toxicity was found and the mice tolerated a dose of 5 g/kg of body weight. Mori et al. (2006)[3] could not find toxicity in rodents for C60 and C70 mixtures after oral administration of a dose of 2 g/kg body weight and did not observe evidence of genotoxic or mutagenic potential in vitro. Other studies could not establish the toxicity of fullerenes: on the contrary, the work of Gharbi et al. (2005)[4] suggested that aqueous C60 suspensions failing to produce acute or subacute toxicity in rodents could also protect their livers in a dose-dependent manner against free-radical damage. In a 2012 primary study of an olive oil / C60 suspension administered to rats by intra-peritoneal administration or oral gavage, a prolonged lifespan to almost double the normal lifespan of the rats was seen and significant toxicity was not observed.[5] An investigator for this study, Professor Moussa, generalized from its findings in a video interview and stated that pure C60 is not toxic.[6]

When considering toxicological data, care must be taken to distinguish as necessary between what are normally referred to as fullerenes: (C60, C70, ...); fullerene derivatives: C60 or other fullerenes with covalently bonded chemical groups; fullerene complexes (e.g., water-solubilized with surfactants, such as C60-PVP; host-guest complexes, such as with cyclodextrin), where the fullerene is supermolecular bound to another molecule; C60 nanoparticles, which are extended solid-phase aggregates of C60 crystallites; and nanotubes, which are generally much larger (in terms of molecular weight and size) molecules, and are different in shape to the spheroidal fullerenes C60 and C70, as well as having different chemical and physical properties.

The molecules above are all fullerenes (close-caged all-carbon molecules) but it is unreliable to extrapolate results from C60 to nanotubes or vice versa, as they range from insoluble materials in either hydrophilic or lipophilic media, to hydrophilic, lipophilic, or even amphiphilic molecules, and with other varying physical and chemical properties. A quantitative structural analysis relationship (QSAR) study can analyze on how close the molecules under consideration are in physical and chemical properties, can help.

Carbon nanotubes

A multiwalled carbon nanotube pierces an alveolar epithelial cell.

As of 2013, the United States National Institute for Occupational Safety and Health was not aware of any reports of adverse health effects in workers using or producing carbon nanotubes or carbon nanofibers. However a systematic review of 54 laboratory animal studies indicated that they could cause adverse 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.[7]

With reference to nanotubes, a 2008 study[8] on carbon nanotubes introduced into the abdominal cavity of mice led the authors to suggest comparisons to "asbestos-like pathogenicity". It should be noted that this was not an inhalation study, though there have been several performed in the past, therefore it is premature to conclude that nanotubes should be considered to have a toxicological profile similar to asbestos. Conversely, and perhaps illustrative of how the various classes of molecules which fall under the general term fullerene cover a wide range of properties, Sayes et al. found that in vivo inhalation of C60(OH)24 and nano-C60 in rats gave no effect, whereas in comparison quartz particles produced an inflammatory response under the same conditions.[9] As stated above, nanotubes are quite different in chemical and physical properties to C60, i.e., molecular weight, shape, size, physical properties (such as solubility) all are very different, so from a toxicological standpoint, different results for C60 and nanotubes are not suggestive of any discrepancy in the findings.

A 2016 study reported on workers in a large-scale MWCNT manufacturing facility in Russia with relatively high occupational exposure levels, finding that exposure to MWCNTs caused significant increase in several inflammatory cytokines and other biomarkers for interstitial lung disease.[10]

Toxicity

The toxicity of carbon nanotubes has been an important question in nanotechnology. As of 2007, such research had just begun. The data is still fragmentary and subject to criticism. Preliminary results highlight the difficulties in evaluating the toxicity of this heterogeneous material. Parameters such as structure, size distribution, surface area, surface chemistry, surface charge, and agglomeration state as well as purity of the samples, have considerable impact on the reactivity of carbon nanotubes. However, available data clearly show that, under some conditions, nanotubes can cross membrane barriers, which suggests that, if raw materials reach the organs, they can induce harmful effects such as inflammatory and fibrotic reactions.[11][12]

Under certain conditions CNTs can enter human cells and accumulate in the cytoplasm, causing cell death.[13]

Results of rodent studies collectively show that regardless of the process by which CNTs were synthesized and the types and amounts of metals they contained, CNTs were capable of producing inflammation, epithelioid granulomas (microscopic nodules), fibrosis, and biochemical/toxicological changes in the lungs.[14] Comparative toxicity studies in which mice were given equal weights of test materials showed that SWCNTs were more toxic than quartz, which is considered a serious occupational health hazard when chronically inhaled. As a control, ultrafine carbon black was shown to produce minimal lung responses.[15]

Carbon nanotubes deposit in the alveolar ducts by aligning lengthwise with the airways; the nanotubes will often combine with metals.[16] The needle-like fiber shape of CNTs is similar to asbestos fibers. This raises the idea that widespread use of carbon nanotubes may lead to pleural mesothelioma, a cancer of the lining of the lungs, or peritoneal mesothelioma, a cancer of the lining of the abdomen (both caused by exposure to asbestos). A recently published pilot study supports this prediction.[17] Scientists exposed the mesothelial lining of the body cavity of mice to long multiwalled carbon nanotubes and observed asbestos-like, length-dependent, pathogenic behavior that included inflammation and formation of lesions known as granulomas. Authors of the study conclude:

This is of considerable importance, because research and business communities continue to invest heavily in carbon nanotubes for a wide range of products under the assumption that they are no more hazardous than graphite. Our results suggest the need for further research and great caution before introducing such products into the market if long-term harm is to be avoided.[17]

Although further research is required, the available data suggest that under certain conditions, especially those involving chronic exposure, carbon nanotubes can pose a serious risk to human health.[11][13][15][17]

In 2014, experts from the International Agency for Research on Cancer (IARC) assessed the carcinogenicity of CNTs, including SWCNTs and MWCNTs. No human epidemiologic or cancer data was available to the IARC Working Group at the time, so the evaluation focused on the results of in vivo animal studies assessing the carcinogenicity of SWCNTs and MWCNTs in rodents.

The Working Group concluded that there was sufficient evidence for the specific MWCNT type “MWCNT-7”, limited evidence for the two other types of MWCNTs with dimensions similar to MWCNT-7, and inadequate evidence for SWCNTs. Therefore, it was agreed to specifically classify MWCNT-7 as possibly carcinogenic to humans (Group 2B) while the other forms of CNT, namely SWCNT and other types of MWCNT, excluding MWCNT-7, were considered not classifiable as to their carcinogenicity to humans (Group 3) due to a lack of coherent evidence.[18]

Epidemiology and Risk Management

Currently, there is a lack of epidemiological evidence linking exposure to CNT to human health effects. To date, there have been only a handful of published epidemiological studies that have solely examined the health effects related to the exposure of CNT, while several other studies are currently underway and yet to be published.[19][20][21] With the limited amount of human data, scientists are more reliant on the results of current animal toxicity studies to predict adverse health effects, as well as applying what is already known about exposures to other fibrous materials such as asbestos or fine and ultra-fine particulates. This limitation of human data has led to the use of the precautionary principle, which urges workplaces to limit exposure levels to CNT as low as possibly achievable in the absence of known health effects data.[22]

To date, several international government agencies, as well as individual authors, have developed occupational exposure limits (OEL) to reduce the risk of any possible human health effects associated with workplace exposures to CNT. The National Institute for Occupational Safety and Health (NIOSH) conducted a risk assessment using animal and other toxicological data relevant to assessing the potential non-malignant adverse respiratory effects of CNT and proposed an OEL of 1 μg/m3 elemental carbon as a respirable mass 8-hour time-weighted average (TWA) concentration.[7] Several individual authors have also performed similar risk assessments using animal toxicity data and have established inhalation exposure limits ranging from 2.5 to 50 ug/m3.[23]

Safety and Exposure Prevention

Occupational exposures that could potentially allow the inhalation of CNT is of the greatest concern, especially in situations where the CNT is handled in powder form which can easily be aerosolized and inhaled. Also of concern are any high-energy processes that are applied to various CNT preparations such as the mixing or sonication of CNT in liquids as well as processes that cut or drill into CNT based composites in downstream products. These types of high-energy processes will aerosolize CNT which can then be inhaled.

Guidance for minimizing exposure and risk to CNT have been published by several international agencies which includes several documents from the British Health and Safety Executive titled "Using nanomaterials at work Including carbon nanotubes and other bio-persistent high aspect ratio nanomaterials" and the "Risk Management of Carbon Nanotubes"[24][25] Safe Work Australia has also published guidance titled "Safe Handling and use of Carbon Nanotubes" which describes two approaches to managing the risks that include risk management with detailed hazard analysis and exposure assessment as well as risk management by using Control Banding.[26] The National Institute for Occupational Safety and Health has also published a document titled "Current Intelligence Bulletin 65: Occupational Exposure to Carbon Nanotubes and Nanofibers" describes strategies for controlling workplace exposures and implementing a medical surveillance program.[7]

These guidance documents generally advocate instituting the principles of the Hierarchy of Hazard Control which is a system used in industry to minimize or eliminate exposure to hazards. The hazard controls in the hierarchy are, in order of decreasing effectiveness:

References

  1. ↑ G. Lalwani and B. Sitharaman, Multifunctional fullerene and metallofullerene based nanobiomaterials, NanoLIFE 08/2013; 3:1342003. DOI: 10.1142/S1793984413420038 Full Text PDF
  2. ↑ Moussa, F.; Trivin, F.; Céolin, R.; Hadchouel, M.; Sizaret, P. Y.; Greugny, V.; Fabre, C.; Rassat, A.; Szwarc, H. (1996). "Early effects of C60 Administration in Swiss Mice: A Preliminary Account for In Vivo C60 Toxicity". Fullerene Science and Technology. 4: 21–29. doi:10.1080/10641229608001534.
  3. ↑ Mori, T.; Takada, H. (2006). "Preclinical studies on safety of fullerene upon acute oral administration and evaluation for no mutagenesis". Toxicology. 225 (1): 48–54. doi:10.1016/j.tox.2006.05.001. PMID 16782258.
  4. ↑ Gharbi, N.; Pressac, M.; Hadchouel, Michelle; Szwarc, Henri; Wilson, Stephen R.; Moussa, Fathi (2005). "[60]fullerene is a powerful antioxidant in vivo with no acute or subacute toxicity". Nano Letters. 5 (12): 2578–85. Bibcode:2005NanoL...5.2578G. doi:10.1021/nl051866b. PMID 16351219.
  5. ↑ Baati, Tarek; Bourasset F; Gharbi N; Njim L; Abderrabba M; Kerkeni A; Szwarc H; Moussa F (June 2012). "The prolongation of the lifespan of rats by repeated oral administration of [60] fullerene" (PDF). Biomaterials. 33 (19): 4936–4946. doi:10.1016/j.biomaterials.2012.03.036. PMID 22498298.
  6. ↑ Moussa, Loera (Director) (8 October 2012). C60 Olive Oil Full Interview With Professor Fathi Moussa Check |url= value (help) (Television production). Paris: Loera, C60.NET.
  7. 1 2 3 "Current Intelligence Bulletin 65: Occupational Exposure to Carbon Nanotubes and Nanofibers". National Institute for Occupational Safety and Health. April 2013. pp. v et al. Retrieved 21 February 2016.
  8. ↑ Poland, C.A.; Duffin, R. (2008). "Carbon nanotubes introduced into the abdominal cavity of mice show asbestos-like pathogenicity in a pilot study". Nature Nanotechnology. 3 (7): 423–8. doi:10.1038/nnano.2008.111. PMID 18654567.
  9. ↑ Sayes, C.M.; Marchione, A. A.; Reed, Kenneth L.; Warheit, David B. (2007). "Comparative Pulmonary Toxicity Assessments of C60 Water Suspensions in Rats: Few Differences in Fullerene Toxicity in Vivo in Contrast to in Vitro Profiles". Nano Letters. 7 (8): 2399–406. Bibcode:2007NanoL...7.2399S. doi:10.1021/nl0710710. PMID 17630811.
  10. ↑ Fatkhutdinova LM, Khaliullin TO, Vasil'yeva OL, Zalyalov RR, Mustafin IG, Kisin ER, Birch ME, Yanamala N, Shvedova AA (2016-05-15). "Fibrosis biomarkers in workers exposed to MWCNTs". Toxicol Appl Pharmacol. 299: 125–31. doi:10.1016/j.taap.2016.02.016. PMID 26902652.
  11. 1 2 Kolosnjaj J, Szwarc H, Moussa F (2007). "Toxicity studies of carbon nanotubes". Adv Exp Med Biol. Advances in Experimental Medicine and Biology. 620: 181–204. doi:10.1007/978-0-387-76713-0_14. ISBN 978-0-387-76712-3. PMID 18217344.
  12. ↑ Corredor, C.; Hou, W.C.; Klein, S.A.; Moghadam, B.Y.; Goryll, M.; Doudrick, K.; Westerhoff, P.; Posner, J.D. (2013). "Disruption of model cell membranes by carbon nanotubes". Carbon. 60: 67–75. doi:10.1016/j.carbon.2013.03.057.
  13. 1 2 Porter, Alexandra; Gass, Mhairi; Muller, Karin; Skepper, Jeremy N.; Midgley, Paul A.; Welland, Mark (2007). "Direct imaging of single-walled carbon nanotubes in cells". Nature Nanotechnology. 2 (11): 713–7. Bibcode:2007NatNa...2..713P. doi:10.1038/nnano.2007.347. PMID 18654411.
  14. ↑ Zumwalde, Ralph and Laura Hodson (March 2009). "Approaches to Safe Nanotechnology: Managing the Health and Safety Concerns Associated with Engineered Nanomaterials". National Institute for Occupational Safety and Health. NIOSH (DHHS) Publication 2009-125.
  15. 1 2 Lam CW, James JT, McCluskey R, Arepalli S, Hunter RL (2006). "A review of carbon nanotube toxicity and assessment of potential occupational and environmental health risks". Crit Rev Toxicol. 36 (3): 189–217. doi:10.1080/10408440600570233. PMID 16686422.
  16. ↑ James D Byrne; John A Baugh (2008). "The significance of nano particles in particle-induced pulmonary fibrosis". McGill Journal of Medicine. 11 (1): 43–50. PMC 2322933Freely accessible. PMID 18523535.
  17. 1 2 3 Poland, CA; Duffin, Rodger; Kinloch, Ian; Maynard, Andrew; Wallace, William A. H.; Seaton, Anthony; Stone, Vicki; Brown, Simon; et al. (2008). "Carbon nanotubes introduced into the abdominal cavity of mice show asbestos-like pathogenicity in a pilot study". Nature Nanotechnology. 3 (7): 423–8. doi:10.1038/nnano.2008.111. PMID 18654567.
  18. ↑ Grosse, Yann (30 October 2014). "Carcinogenicity of fluoro-edenite, silicon carbide fibres and whiskers, and carbon nanotubes". The Lancet Oncology. 15: 1427–1428. doi:10.1016/S1470-2045(14)71109-X.
  19. ↑ Fatkhutdinova, Liliya M.; Khaliullin, Timur O.; Vasil'yeva, Olga L.; Zalyalov, Ramil R.; Mustafin, Ilshat G.; Kisin, Elena R.; Birch, M. Eileen; Yanamala, Naveena; Shvedova, Anna A. "Fibrosis biomarkers in workers exposed to MWCNTs". Toxicology and Applied Pharmacology. 299: 125–131. doi:10.1016/j.taap.2016.02.016.
  20. ↑ Lee, Jong Seong; Choi, Young Chul; Shin, Jae Hoon; Lee, Ji Hyun; Lee, Yurim; Park, So Young; Baek, Jin Ee; Park, Jung Duck; Ahn, Kangho (18 August 2015). "Health surveillance study of workers who manufacture multi-walled carbon nanotubes". Nanotoxicology. 9 (6): 802–811. doi:10.3109/17435390.2014.978404. ISSN 1743-5390. PMID 25395166.
  21. ↑ Liou, Saou-Hsing; Tsai, Candace S. J.; Pelclova, Daniela; Schubauer-Berigan, Mary K.; Schulte, Paul A. (19 October 2015). "Assessing the first wave of epidemiological studies of nanomaterial workers". Journal of Nanoparticle Research. 17 (10): 1–19. doi:10.1007/s11051-015-3219-7. ISSN 1388-0764. PMC 4666542Freely accessible. PMID 26635494.
  22. ↑ Schulte, Paul A.; Kuempel, Eileen D.; Zumwalde, Ralph D.; Geraci, Charles L.; Schubauer-Berigan, Mary K.; Castranova, Vincent; Hodson, Laura; Murashov, Vladimir; Dahm, Matthew M. (1 May 2012). "Focused actions to protect carbon nanotube workers". American Journal of Industrial Medicine. 55 (5): 395–411. doi:10.1002/ajim.22028. ISSN 1097-0274.
  23. ↑ Broekhuizen, Pieter Van; Veelen, Wim Van; Streekstra, Willem-Henk; Schulte, Paul; Reijnders, Lucas (1 July 2012). "Exposure Limits for Nanoparticles: Report of an International Workshop on Nano Reference Values". Annals of Occupational Hygiene. 56 (5): 515–524. doi:10.1093/annhyg/mes043. ISSN 0003-4878. PMID 22752096.
  24. ↑ "Using nanomaterials at work". www.hse.gov.uk. Retrieved 21 February 2016.
  25. ↑ "Risk management basics - Nanotechnology - HSE". www.hse.gov.uk. Retrieved 21 February 2016.
  26. ↑ "Safe handling and use of carbon nanotubes - Safe Work Australia". www.safeworkaustralia.gov.au. Retrieved 21 February 2016.

Further reading

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