Development of a testing method for asbestos fibers in treated materials of asbestos containing wastes by transmission electron microscopy

Our plain-English summary of Development of a testing method for asbestos fibers in treated materials of asbestos containing wastes by transmission electron microscopy, by T. Yamamoto, A. Kida, Y. Noma, et al (Waste Management, 2014).

The study

• Authors: T. Yamamoto, A. Kida, Y. Noma, A. Terazono, S. Sakai
• Journal: Waste Management
• Published: 2014;34(2):536-41
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Appropriate treatment of asbestos-containing wastes is a significant problem. In Japan, the inertization of asbestos-containing wastes based on new treatment processes approved by the Minister of the Environment is promoted. A highly sensitive method for testing asbestos fibers in inertized materials is required so that these processes can be approved. We developed a method in which fibers from milled treated materials are extracted in water by shaking, and are counted and identified by transmission electron microscopy. Evaluation of this method by using asbestos standards and simulated slag samples confirmed that the quantitation limits are a few million fibers per gram and a few μg/g in a sample of 50mg per filter. We used this method to assay asbestos fibers in slag samples produced by high-temperature melting of asbestos-containing wastes. Fiber concentrations were below the quantitation limit in all samples, and total fiber concentrations were determined as 47-170×10(-6) f/g. Because the evaluation of treated materials by TEM is difficult owing to the limited amount of sample observable, this testing method should be used in conjunction with bulk analytical methods for sure evaluation of treated materials.

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In plain English

This Japanese laboratory methods study developed a test for asbestos fibers remaining in treated asbestos waste. Treated material was ground, shaken in water and examined by transmission electron microscopy (TEM). The authors tested it in two laboratories using chrysotile, amosite and crocidolite standards and spiked slag extracts. Fiber counts agreed between laboratories except for chrysotile-spiked slag, where lab B's count was about three times lab A's; weight estimates did not agree. In spiked slag, weights ranged from 22% to 410% (lab A) and 140% to 770% (lab B) of the amounts added. The authors reported the method could measure a few million fibers per gram with about 30% precision. They then tested eight slag samples from three high-temperature melting furnaces, some fed wastes with asbestos added. Asbestos fibers were below the quantitation limit in every sample; one chrysotile fiber was seen in one sample. Non-asbestos fibers measured 47 to 170 million per gram. The authors concluded the method should be used with bulk methods such as dispersion staining and X-ray diffraction, because TEM examines only small amounts of sample.

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 analytical method development and validation study, including a two-laboratory comparison
• Who was studied: Eight slag samples from three types of high-temperature melting furnaces (plants A, B and C) in Japan, plus asbestos standards and simulated slag samples made by spiking slag extracts with asbestos standards
• Exposure: Chrysotile (JAWE 131), crocidolite (UICC) and amosite (UICC) standards. In the melted wastes: asbestos packing (67% chrysotile by weight), asbestos slate (12% chrysotile) and, per Table 1, sprayed asbestos, added to automobile shredder residue, plastic wastes or ash
• Main results:
  • Repeated TEM measurement of a chrysotile standard (40 micrograms per filter) gave an average fiber concentration of 7.5 × 10^12 fibers per gram with a relative standard deviation of 34%. Weight estimates averaged 45 micrograms per filter (range 17 to 97) with a relative standard deviation of 55%.
  • For the asbestos standards, measured weight as a percentage of the prepared amount was 120% (lab A) for chrysotile, 80% (lab A) and 290% (lab B) for amosite, and 170% (lab A) and 200% (lab B) for crocidolite.
  • In slag extracts spiked with chrysotile, lab B measured a fiber concentration about three times that measured by lab A. The amosite and crocidolite spiked-extract fiber results were consistent between laboratories.
  • In slag extracts spiked with asbestos, weight estimates were not consistent and ranged from 22% to 410% of the prepared amounts in lab A and from 140% to 770% in lab B. No asbestos fibers were found in unspiked slag extracts.
  • The authors reported the method can determine asbestos fiber concentration in treated materials at a few million fibers per gram with a precision of about 30%, and weight concentration at a few micrograms per gram when 50 mg of material is on each filter.
  • In all eight slag samples, asbestos fiber concentrations were below the quantitation limit.
  • One fiber identified as chrysotile was found, in slag sample No. 2 (automobile shredder residue plus asbestos slate). The concentration for that sample was still below the quantitation limit.
  • Non-asbestos fibers, such as glass fragments from slag particles, were found in the slag samples at 47 to 170 × 10^6 fibers per gram.
  • Dispersion staining and X-ray diffraction testing of the same slag samples found no asbestos in any sample.
• The authors' conclusion: The authors concluded that the TEM method should be used together with bulk analytical methods such as dispersion staining and X-ray diffraction to evaluate treated materials, because TEM can examine only a limited amount of sample.
• Limitations the authors state:
  • Weight concentration estimates were not consistent between laboratories and were far from the prepared amounts, so the authors noted a problem with accuracy for weight measurement.
  • TEM cannot practically examine treated material comprehensively, because only a small amount of sample can be observed.

Topics

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

Medical terms in this study, explained in our Lexicon: Transmission Electron Microscopy (TEM), Fibers Per Gram.

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