How are the physical and chemical properties of chrysotile asbestos altered by a 10-year residence in water and up to 5 days in simulated stomach acid?

Our plain-English summary of How are the physical and chemical properties of chrysotile asbestos altered by a 10-year residence in water and up to 5 days in simulated stomach acid?, by K. Seshan (Environmental Health Perspectives, 1983).

The study

• Author: K. Seshan
• Journal: Environmental Health Perspectives
• Published: 1983;53:143-8
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Although there have been a number of studies on the ingestion of asbestos, few studies exist on how the chrysotile asbestos itself is altered by the exposure to the acid stomach environment. This study has found that there are changes in the physical, chemical and surface properties of chrysotile asbestos as a result of exposure to water, strong acids, and simulated gastric juices. It was observed that the charge on the surface (the zeta potential) is changed from positive to negative; the surface becomes silicalike; and the magnesium is lost from the fibers of asbestos upon exposure to water and acid. It was also noted that the smaller the fiber diameter, the faster the loss of the magnesium. Notable among the changes in physical properties is a change in the refractive index. This means that asbestos exposed to acids or water may not be detectable using the dispersion staining techniques that identify asbestos based on the refractive index. Other physical property changes include the destruction of the gross crystallinity of the fibers. The x-ray diffraction signal disappears when fibers are exposed to acid. However, this study shows that the fibers may still be detected by electron diffraction. It appears that upon acid exposure, the magnesium ions are leached out, leaving a magnesium-free silica network. A positive ion, possibly the proton (H+) or the hydronium ion (H3O+), replaces the lost magnesium ion.

In plain English

This laboratory study from the University of Arizona examined how chrysotile asbestos fibers change after long storage in water and after exposure to acid. Chrysotile from three sources (UICC, NIEHS, and Globe, Arizona) was kept in distilled water for 10 years, in 1 N hydrochloric acid for half an hour to 5 days, or in simulated gastric juice (pH 1.2) for up to 5 days. In simulated gastric juice the fibers' surface charge changed from positive to negative in less than 1 hour. In 1 N hydrochloric acid it was still positive after 8 hours. Acid leached magnesium from the fibers, made the surface silica-like, and lowered the refractive index from 1.54 to 1.44. Smaller fibers lost magnesium faster. Acid destroyed chrysotile's X-ray diffraction pattern but did not change crocidolite's. Electron diffraction still identified most treated fibers. The author concluded that chrysotile's physical, chemical and surface properties change after acid exposure. The author noted that the simulated gastric juice lacked some components of human stomach acid.

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 experiment on chrysotile asbestos fibers exposed to water, acid and simulated gastric juice
• Who was studied: Chrysotile asbestos samples from three sources: International Union Against Cancer (UICC), National Institute of Environmental Health Sciences (NIEHS), and Globe, Arizona
• Exposure: Chrysotile kept in doubly distilled water for 10 years, in 1 N hydrochloric acid for intervals from half an hour to 5 days, and in simulated gastric juice (sodium chloride, pepsin and hydrochloric acid in water, pH 1.2) for up to 5 days. Some tests used 0.1 N hydrochloric acid.
• Main results:
  • In simulated gastric juice, the zeta potential (surface charge) of NIEHS, UICC and Globe chrysotile went from positive to negative in less than 1 hour
  • In 1 N hydrochloric acid, the zeta potential was still positive after 8 hours
  • The zero point of charge moved from pH 6.5 for untreated fibers to pH 4 for 0.1 N hydrochloric acid-treated chrysotile, which the author interpreted as the surface becoming silica-like
  • After 2 hours in 1 N hydrochloric acid, the surface area of NIEHS chrysotile was about double that of untreated fibers (59.82 vs 29.76 square meters per gram)
  • The surface area of Globe chrysotile was not affected by the acid treatment (29.55 untreated vs 30.99 square meters per gram)
  • With 1 N hydrochloric acid and simulated gastric juice treatment, the refractive index decreased from 1.54 for untreated fibers to 1.44 for treated fibers
  • The author suggested that methods identifying chrysotile by refractive index alone will not be effective for acid-treated fibers
  • The X-ray diffraction signal of chrysotile disappeared after acid exposure (shown after 3 and 5 days in 1 N hydrochloric acid)
  • Crocidolite, an amphibole, remained unchanged on X-ray diffraction after 1 N hydrochloric acid treatment
  • Percent of chrysotile fibers identifiable by electron diffraction (untreated, then 30 minutes and 5 days in 1 N hydrochloric acid): UICC 89, 67, 60; NIEHS 90, 80, 77; Globe 92, 87, 80
  • After 5 days in 1 N hydrochloric acid, electron diffraction patterns lost clarity, which the author assumed was related to magnesium loss
  • Atomic absorption analysis of the treatment liquid showed that acid leaches magnesium from chrysotile fibers
  • The smaller the fiber diameter, the faster the magnesium loss
• The authors' conclusion: The author concluded that chrysotile from the three sources changes its physical, chemical and surface properties after exposure to hydrochloric acid and simulated gastric juice. The author also stated that new techniques will be needed to identify fibers after ingestion.
• Limitations the authors state:
  • The simulated gastric juice did not contain all components of human stomach acid. Organic compounds such as muco- and glycoproteins might coat fibers and affect surface charge and magnesium leaching.

Topics

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

Medical terms in this study, explained in our Lexicon: Chrysotile, Refractive Index, dispersion staining, X-Ray Diffraction (XRD).

Related studies

• Mesotheliomas in rats following inoculation with acid-leached chrysotile asbestos and other mineral fibres — G. Monchaux, J. Bignon, et al. (1981)
• Surface physico-chemical studies of chrysotile asbestos and related minerals — C. Jolicoeur, D. Poisson (1987)
• The effects of naturally occurring acids on the surface properties of chrysotile asbestos — E.P. Holmes, L.M. Lavkulich (2014)
• Variation of properties of chrysotile asbestos subjected to milling — A.M. Langer, M.S. Wolff, et al. (1978)
• Origin and fate of nanoparticles in marine water - Preliminary results — B. Graca, A. Zgrundo, et al. (2018)
• A new approach to the decontamination of asbestos-polluted waters by treatment with oxalic acid under power ultrasound — F. Turci, M. Tomatis, et al. (2008)

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