Quantitative relationship of fecal asbestos to asbestos exposure

Our plain-English summary of Quantitative relationship of fecal asbestos to asbestos exposure, by H.M. Cunningham, R.D. Pontefract, R.C. O'Brien (Journal of Toxicology and Environmental Health, 1976).

The study

• Authors: H.M. Cunningham, R.D. Pontefract, R.C. O'Brien
• Journal: Journal of Toxicology and Environmental Health
• Published: 1976;1(3):377-9
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

A method is descirbed for isolating chrysotile fibers from feces and counting them with an electron microscope. The detection limit was 150,000 fibers per gram feces; average recovery was 85.5%. When the method was used to check the asbestos in feces of people subjected to industrial exposure vs. controls, the means were significantly different (p less than 0.02). Duplicate fecal samples were found to check within an average of +/- 31.1% of their means.

In plain English

This 1976 report from Canada's Health Protection Branch described a method for separating chrysotile asbestos fibers from human feces and counting them by electron microscope, and tested it on workers and controls. One stool sample each came from six people estimated to have high industrial exposure to chrysotile, six estimated to have moderate exposure, and 12 laboratory technicians in Ottawa as controls. The detection limit was 150,000 fibers per gram, and average recovery of fibers added to test samples was 85.5%. Levels varied considerably within groups. Averages were 26.47 million fibers per gram for the high group, 11.93 million for the moderate group and 0.37 million for the technicians. The 12 industrially exposed people differed significantly from the technicians (p less than 0.02), but no significant difference was detected between high and moderate exposure. Fiber length was measured in four samples per exposed group and seven technicians' samples. Among these, fibers over 5 micrometres appeared only in the technician with the highest level. The authors concluded that fecal analysis quantitatively estimates total body exposure and could help identify continuously exposed people.

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 method development, with a small comparison of exposed workers and unexposed controls
• Who was studied: One fecal sample each from 12 people with industrial exposure and 12 control technicians. Of the exposed people, six were estimated to have high industrial exposure to chrysotile and six moderate exposure. Their samples were taken after 2 successive days of work and were provided through the Thetford Industrial Clinic, Thetford Mines, Québec, and the Health Protection Branch. The controls were technicians at the authors' Food Research Laboratories in Ottawa.
• Exposure: Industrial exposure to chrysotile asbestos, classed as high or moderate by estimate. No exposure measurements are reported.
• Main results:
  • The detection limit of the method was 150,000 fibers per gram of feces.
  • High-exposure group (6 people): 4.03 to 92.99 x 10^6 fibers per gram, average 26.47 x 10^6.
  • Moderate-exposure group (6 people): 0.51 to 33.50 x 10^6 fibers per gram, average 11.93 x 10^6.
  • Control technicians (12 people): 0.00 to 1.70 x 10^6 fibers per gram, average 0.37 x 10^6.
  • Fecal chrysotile in the 12 industrially exposed people differed significantly from the 12 technicians (p less than 0.02).
  • No significant difference was detected between the high and moderate exposure groups.
  • Recovery of added fibers averaged 99.8% at a spike of 6.89 x 10^6 fibers per gram and 71.2% at six times that level, for an average of 85.5% over four determinations.
  • Duplicate analyses, made on five high-level samples, five moderate-level samples and seven technicians' samples that were above the detection limit, agreed within an average of plus or minus 31.1% of their means.
  • Fiber length distributions were obtained on four fecal samples from each of the two industrially exposed groups and on seven technicians. Fiber lengths did not differ between the high and moderate groups.
  • Among the samples measured for fiber length, fibers longer than 5.0 micrometres were found only in the technician with the highest fecal asbestos level, who did not know where he had been exposed.
• The authors' conclusion: The authors concluded that fecal analysis quantitatively estimates total body exposure. They said it should provide a useful means of identifying individuals and populations continuously exposed to asbestos from a variety of sources.
• Limitations the authors state:
  • Recovery was incomplete because ash particles not fully dissolved during extraction can hide some fibers under the electron microscope.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Chrysotile, Fibers Per Gram.

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