In vitro cytotoxicity and transforming potential of industrial carbon dust (fibers and particles) in syrian hamster embryo (SHE) cells

Our plain-English summary of In vitro cytotoxicity and transforming potential of industrial carbon dust (fibers and particles) in syrian hamster embryo (SHE) cells, by C. Darne, F. Terzetti, C. Coulais, et al (The Annals of Occupational Hygiene, 2010).

The study

• Authors: C. Darne, F. Terzetti, C. Coulais, J. Fournier, Y. Guichard, L. Gaté, S. Binet
• Journal: The Annals of Occupational Hygiene
• Published: 2010;54(5):532-44
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Carbon fibers have many applications, mainly in high-tech industries such as the aviation industry. Eleven carbon samples (fibers and particles) coming from an aeronautic group were tested for their cytotoxicity and carcinogenic potential using in vitro short-term assays in Syrian hamster embryo cells. These samples were taken during each important step of the process, i.e. from the initial heating of polyacrylonitrile fibers to pure carbon fibers. They were compared to an asbestos fiber, an amorphous silica, and two commercial graphite powders. Their physical-chemical characteristics and their capacity to release reactive oxygen species (ROS) were determined. This study showed that none of the carbon samples was able to generate ROS as measured by Electron Paramagnetic Resonance analysis, and in our biological assays, they demonstrated no morphological transformation potential and low cytotoxicity compared to positive control (chrysotile asbestos).

In plain English

This was a laboratory study in Syrian hamster embryo cells, not people. The authors tested eleven carbon dust samples from Safran aeronautic plants: nine from successive production steps, one from machining a finished piece and one from a test bench. They compared them with chrysotile asbestos (the positive control), amorphous silica, two graphite powders and aluminum oxide. The nine production-step samples were ground before testing. Apart from weak activity in E1 and E10, which the authors called negligible next to chrysotile, no carbon sample released reactive oxygen species. Chrysotile cut cell growth by half at 1.63 micrograms per square centimeter. No carbon sample did so, even at the highest dose of 28.58. In the colony assay, E11 at 28.5 micrograms per square centimeter cut colony formation by 60.81% versus untreated cells. Chrysotile caused dose-related cell transformation. None of samples E1 to E11 caused significant transformation, though one commercial graphite gave four transformed colonies in one of three experiments. The authors concluded that the carbon samples showed no transforming potential and low cytotoxicity compared with chrysotile. They said results from one process need confirming with other samples.

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: Laboratory (in vitro) experiment using short-term cell assays in Syrian hamster embryo cells, plus chemical tests of reactive oxygen species release
• Who was studied: Eleven PAN-based carbon dust samples (E1 to E11) from Safran aeronautic plants (Messier-Bugatti and Snecma Propulsion Solide) in France. E1 to E9 came from successive fabrication steps, E10 from machining a final carbon piece and E11 from a test bench. The samples were tested on SHE cells established from 13-day gestation hamster fetuses.
• Exposure: The carbon fibers and particles came from different sources. E1 to E5 came from the first steps (heating below 1000°C) and E6 to E9 from intermediate steps (heating above 1000°C). E10 came from machining a final carbon piece and E11 from a test bench. E1 to E9 were ground in a corundum jar. The comparison materials were UICC chrysotile (code C19, positive control), amorphous diatomaceous earth, two commercial graphites and corundum aluminum oxide. For the carbon samples, doses ranged from 0.045 to 28.58 micrograms per square centimeter in the proliferation assay and from 4.75 to 28.5 in the transformation assay.
• Main results:
  • The carbon samples did not release reactive oxygen species, except for weak production by E1 and E10 that remained negligible compared with chrysotile.
  • After 72 hours, the concentration that halved cell proliferation (IC50) was 1.63 micrograms per square centimeter for chrysotile, versus 6.8 for diatomaceous earth.
  • No carbon sample from E1 to E11 reached the IC50, even at the highest concentration of 28.58 micrograms per square centimeter. The most inhibitory sample at that dose was E2, at 49% inhibition.
  • At 28.5 micrograms per square centimeter, E11 reduced colony formation by 60.81% compared with control (relative plating efficiency 39%), which the authors reported as cell lethality. E11 was the only carbon sample that caused a 50% loss of colonies (LC50 23.56 micrograms per square centimeter).
  • Chrysotile produced transformed colonies from 0.38 micrograms per square centimeter, and transformation frequency rose with concentration. At 3.8 it reached 0.826% (9 transformed of 1089 colonies), versus 0.043% (5 of 11,512) in control cultures.
  • None of the industrial samples E1 to E11 caused significant cell transformation. The exception the authors noted was four transformed colonies with a commercial graphite in only one of three experiments. Table 3 shows these for G28286-3 at 7.6 micrograms per square centimeter (0.170%, 4 of 2352 colonies) and marks the result as statistically significant.
  • No relationship was found between cell proliferation and fiber percentage, fiber or particle size, or ROS generation.
  • Aluminum oxide (the grinding contaminant) caused no cell lethality or transformation on its own. Mixing it with chrysotile at 1, 25 or 50% of chrysotile mass did not change chrysotile's effects.
• The authors' conclusion: The authors concluded that, in their conditions, the carbon samples showed no morphological transformation potential in the SHE assay and had low cytotoxicity compared with chrysotile asbestos.
• Limitations the authors state:
  • All samples came from one type of production process. The authors said the results should be confirmed with samples from other firms and from other methods.
  • Air sampling was not feasible, and the samples as collected were not of respirable size, so E1 to E9 were crushed before testing.
  • Grinding contaminated samples E1 to E9 with aluminum oxide, at 1.1 to 47.9% of sample mass.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile.

Medical terms in this study, explained in our Lexicon: Carcinogenic, Reactive Oxygen Species (ROS), Chrysotile.

Related studies

• Kerosene soot genotoxicity: enhanced effect upon co-exposure with chrysotile asbestos in Syrian hamster embryo fibroblasts — M. Lohani, E. Dopp, et al. (2000)
• Mineral fibers induce apoptosis in Syrian hamster embryo fibroblasts — E. Dopp, B. Nebe, et al. (1995)
• Asbestos and benzo(a)pyrene synergism in the transformation of Syrian hamster embryo cells — J.A. DiPaolo, A.J. DeMarinis, et al. (1983)
• Characterization of activated proto-oncogenes in chemically transformed Syrian hamster embryo cells — T.M. Gilmer, L.A. Annab, et al. (1988)
• Morphological transformation of Syrian hamster embryo cells induced by mineral fibres and the alleged enhancement of benzo[a]pyrene — S.O. Mikalsen, E. Rivedal, et al. (1988)
• Detection of aneuploidy-inducing carcinogens in the Syrian hamster embryo (SHE) cell transformation assay — D.P. Gibson, M.J. Aardema, et al. (1995)

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