Toxicity of nanomaterials

Our plain-English summary of Toxicity of nanomaterials, by S. Sharifi, S. Behzadi, S. Laurent, et al (Chemical Society Reviews, 2012).

The study

• Authors: S. Sharifi, S. Behzadi, S. Laurent, M.L. Forrest, P. Stroeve, M. Mahmoudi
• Journal: Chemical Society Reviews
• Published: 2012;41(6):2323-43
• Type of article: Review
• Cited by: 798 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Nanoscience has matured significantly during the last decade as it has transitioned from bench top science to applied technology. Presently, nanomaterials are used in a wide variety of commercial products such as electronic components, sports equipment, sun creams and biomedical applications. There are few studies of the long-term consequences of nanoparticles on human health, but governmental agencies, including the United States National Institute for Occupational Safety and Health and Japan's Ministry of Health, have recently raised the question of whether seemingly innocuous materials such as carbon-based nanotubes should be treated with the same caution afforded known carcinogens such as asbestos. Since nanomaterials are increasing a part of everyday consumer products, manufacturing processes, and medical products, it is imperative that both workers and end-users be protected from inhalation of potentially toxic NPs. It also suggests that NPs may need to be sequestered into products so that the NPs are not released into the atmosphere during the product's life or during recycling. Further, non-inhalation routes of NP absorption, including dermal and medical injectables, must be studied in order to understand possible toxic effects. Fewer studies to date have addressed whether the body can eventually eliminate nanomaterials to prevent particle build-up in tissues or organs. This critical review discusses the biophysicochemical properties of various nanomaterials with emphasis on currently available toxicology data and methodologies for evaluating nanoparticle toxicity (286 references).

In plain English

This critical review, not an original study, summarized published research (286 references), emphasizing animal studies and testing methods, on the toxicity of nanomaterials such as metal oxides, gold, silver, quantum dots and carbon nanotubes. The authors did no asbestos research of their own. They noted that government agencies had asked whether carbon nanotubes deserved the caution given known carcinogens such as asbestos, and that some earlier nanoparticle toxicity studies had focused on asbestos and carbon black. The authors wrote that most nanoparticle toxicity arises from excess reactive oxygen species, and that some laboratory cell tests correlated poorly with animal results. In the reviewed studies, lung toxicity tended to rise as particle size fell, and shape, surface charge and chemical makeup also mattered. One cited study reported that long multi-walled carbon nanotubes placed in animals' abdomens could inflame the abdominal wall. Another reported that clumped carbon nanotubes changed a mesothelioma cell line similarly to asbestos. The authors noted that animal data on size effects and on nanoparticle metabolism were scarce. They concluded that inhaled airborne nanoparticles, including carbon-based materials, are of concern.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Critical review of published literature on nanomaterial toxicity (no new data collected)
• Who was studied: No study population; the review covered published laboratory, animal (mostly rodent and zebrafish) and some human studies of nanoparticles, citing 286 references
• Exposure: Engineered nanoparticles of many kinds, including carbon nanotubes, quantum dots, gold, silver, titanium dioxide, silica and iron oxide. The authors did no asbestos research of their own. Asbestos appears as a known carcinogen that government agencies (US NIOSH and Japan's Ministry of Health) compared with carbon nanotubes, and as a subject of some earlier toxicity studies, which the authors judged inadequate to predict the behavior of more complex nanoparticles
• Main results:
  • The authors wrote that most toxicity from nanoparticles in cells and animals arises from excess reactive oxygen species
  • Studies reviewed showed little correlation between laboratory (in vitro) and animal (in vivo) toxicity for some nanomaterials
  • Across the studies reviewed, smaller particle size tended to go with greater lung toxicity
  • A cited study (Poland et al.) reported that long multi-walled carbon nanotubes instilled into the abdomen of animals could cause inflammation of the abdominal wall; short ones did not cause an inflammatory response
  • A cited study (Wick et al.) reported that agglomerated carbon nanotubes changed the morphology and performance of a mesothelioma cell line in a way similar to asbestos
  • The authors judged that nanoparticle toxicity is not simply a result of small size; several characteristics, including composition, surface charge, size and shape, affect it
  • Cationic (positively charged) surfaces are generally believed to be more toxic than anionic (negatively charged) surfaces
• The authors' conclusion: The authors concluded that inhaled airborne nanoparticles, including carbon-based materials, are of concern, and that workers and end-users need protection from inhaling potentially toxic nanoparticles
• Limitations the authors state:
  • Few published data exist on how particle size affects toxicity in living animals
  • There are very few reports on how the body metabolizes nanoparticles
  • Most knowledge of shape-dependent toxicity comes from laboratory (in vitro) experiments

Related studies

• Toxicity evaluations of various carbon nanomaterials — M. Uo, T. Akasaka, et al. (2011)
• The iron-related molecular toxicity mechanism of synthetic asbestos nanofibres: a model study for high-aspect-ratio nanoparticles — F. Turci, M. Tomatis, et al. (2011)
• Cell entry of one-dimensional nanomaterials occurs by tip recognition and rotation — X. Shi, A. von dem Bussche, et al. (2011)
• Cytotoxic effects of aggregated nanomaterials — K. Soto, K.M. Garza, et al. (2007)
• Biopersistence and potential adverse health impacts of fibrous nanomaterials: what have we learned from asbestos? — V.C. Sanchez, J.R. Pietruska, et al. (2009)
• Biopersistent fiber-induced inflammation and carcinogenesis: lessons learned from asbestos toward safety of fibrous nanomaterials — H. Nagai, S. Toyokuni (2010)

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