Evaluation of cellular toxicity of TAFMAG, a natural substitute for asbestos from China

Our plain-English summary of Evaluation of cellular toxicity of TAFMAG, a natural substitute for asbestos from China, by H.J. Kim, H.Y. Nam, Y. Hiroshi, et al (Toxicology Letters, 2005).

The study

• Authors: H.J. Kim, H.Y. Nam, Y. Hiroshi, Y. Shinohara, N. Kohyama, H.K. Yun, Y. Lim, J.S. Song
• Journal: Toxicology Letters
• Published: 2005;155(1):65-71
• Read it: PubMed · Publisher

Abstract

Asbestos is a very important material for industrial use. However, the need for a substitute for asbestos fiber is currently on the rise due to its high disease causing potential. This study evaluated the potential bio-hazardous effects of TAFMAG, a natural fibrous silicate produced in China, in comparison with chrysotile, a typical toxic asbestos. The physicochemical properties of TAFMAG were very similar to those of chrysotile when it was examined by a scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses. Both of TAFMAG and chrysotile showed high content of magnetite and Fenton activity when compared with wollastonite, a non-asbestos fiber with a known low toxicity. When their cellular toxicity was assessed, TAFMAG showed no or less comparable to that of chrysotile in the hemolysis and lipid peroxidation of erythrocytes, and also on a MTT assay in RLE-6TN, a rat alveolar epithelial cell line. Pre-treatment of fibers with desferrioxamine, an iron chelator, showed that iron content of TAFMAG and chrysotile might be important in their cellular toxicity. These results suggest that TAFMAG is potentially toxic when inhaled into the lung and appropriate laws and regulations should be established for its use.

In plain English

This was a laboratory study of TAFMAG, the trade name of a natural mineral fiber from China. The authors said it was imported into Korea without official toxicity inspection. They tested two TAFMAG samples (T-Y-20 and T-4-20) against UICC chrysotile asbestos and against wollastonite, a fiber of known low toxicity. The tests used human red blood cells and a rat lung cell line. X-ray analysis of T-Y-20 found a mixture whose most abundant component was chrysotile, roughly estimated at 60%, followed by brucite at 35%. TAFMAG fibers were generally shorter than the chrysotile. About twice as much surface iron came off the TAFMAG samples as off chrysotile, and they generated more reactive oxygen species. Compared with chrysotile, TAFMAG burst fewer red blood cells, caused similar oxidation damage to red cell membranes, and was slightly less toxic to the lung cells. It was more active than wollastonite in these tests. Removing surface iron reduced some of these effects. The authors concluded that TAFMAG's toxic potential was much higher than wollastonite's and comparable to chrysotile's.

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) study comparing the composition, iron content, oxidant generation and cell toxicity of TAFMAG fibers with chrysotile (positive control) and wollastonite (negative control)
• Who was studied: Two TAFMAG samples (T-Y-20 and T-4-20) obtained from the Korea Industrial Safety Cooperation, compared with UICC chrysotile and wollastonite. They were tested on human red blood cells (erythrocytes) and on RLE-6TN, a rat alveolar epithelial cell line.
• Exposure: TAFMAG, a natural mineral fiber from China whose most abundant component was chrysotile, with brucite second. Cells were exposed to the fibers at increasing concentrations (0, 10, 100 and 1000; units garbled in the text), with and without iron removal by desferrioxamine.
• Main results:
  • In the TAFMAG sample, chrysotile and brucite were estimated from the X-ray pattern at about 60% and 35% by weight respectively, with about 5% other impurities (pyroaurite, quartz, magnetite).
  • TAFMAG fibers were shorter than chrysotile. Fibers in the longest length category (over 20) made up 41.1% of chrysotile, 5.4% of T-Y-20, 0.7% of T-4-20 and 0.8% of wollastonite.
  • Surface iron released (nmol Fe per mg fiber) was 86.92 for T-Y-20 and 108.10 for T-4-20, compared with 48.75 for chrysotile and 0.93 for wollastonite.
  • Both TAFMAG samples generated more reactive oxygen species than chrysotile in a Fenton reaction. Pre-treatment with desferrioxamine significantly reduced this activity for TAFMAG and chrysotile.
  • Red blood cell bursting (hemolysis) by the two TAFMAG samples was much higher than by wollastonite but less than by chrysotile. Iron removal reduced hemolysis by chrysotile and both TAFMAG samples.
  • In the red blood cell lipid peroxidation test (oxidation damage to cell membranes), TAFMAG was as effective as chrysotile. Iron removal only slightly reduced this effect.
  • Toxicity to the rat lung cell line RLE-6TN was slightly lower for both TAFMAG samples than for chrysotile, but much higher than for wollastonite.
• The authors' conclusion: The authors concluded that TAFMAG had a toxic potential much higher than wollastonite and comparable to chrysotile, and suggested careful examination before industrial use of non-asbestos fibers.
• Limitations the authors state:
  • The percentages of chrysotile and brucite in TAFMAG were estimated visually, not measured precisely.
  • Desferrioxamine may not have removed all the iron, because it binds ferric iron in preference to the ferrous iron that matters in the Fenton reaction.
  • The effect of iron removal on lung cell toxicity could not be assessed, because desferrioxamine is itself toxic to the cells.
  • The shorter length of the TAFMAG fibers might mean lower toxicity than chrysotile when actually inhaled into the lung.

Topics

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

Medical terms in this study, explained in our Lexicon: Silicate, Chrysotile, X-Ray Diffraction (XRD), Wollastonite.

Related studies

• Cell toxicity, hemolytic action and clastogenic activity of asbestos and its substitutes — K. Koshi, N. Kohyama, et al. (1991)
• The ability of mineral dusts and fibres to initiate lipid peroxidation. Part I: parameters which determine this ability — M. Gulumian (1999)
• Pulmonary toxicity of wollastonite in vivo and in vitro — E. Tátrai, Z. Kováciková, et al. (2004)
• Potential toxicity of nonregulated asbestiform minerals: balangeroite from the western Alps. Part 1: Identification and characterization — C. Groppo, M. Tomatis, et al. (2005)
• Cytotoxicity of respirable dusts from industrial minerals: comparison of two naturally occurring and two man-made silicates — D. Nadeau, L. Fouquette-Couture, et al. (1987)
• Potential toxicity of nonregulated asbestiform minerals: balangeroite from the western Alps. Part 2: Oxidant activity of the fibers — F. Turci, M. Tomatis, et al. (2005)

Browse more research in Toxicology Letters, or return to medical research.