Chrysotile biopersistence in the lungs of persons in the general population and exposed workers

Our plain-English summary of Chrysotile biopersistence in the lungs of persons in the general population and exposed workers, by A.M. Langer, R.P. Nolan (Environmental Health Perspectives, 1994).

The study

• Authors: A.M. Langer, R.P. Nolan
• Journal: Environmental Health Perspectives
• Published: 1994;102 Suppl 5(Suppl 5):235-9
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Lung burden analysis was performed on 126 autopsy cases of persons who died in New York City from 1966 through 1968. Of the 126 cases, 107 were probably non-occupationally exposed, judging by occupational history and asbestos body content of lung. Fifty-three of the 107 cases contained short chrysotile fibers/fibrils, < 5 microns in length, present in 3-fold greater amounts than were found in laboratory background controls. The fiber concentrations ranged from 1.8 to 15.7 x 10(6) f/gm/dry lung tissue, and the proportion of fibers > or = 5 microns in length was only 0.34% of the total chrysotile population found. Other inorganic particles present included fragments of amphiboles. In contrast to these data, the lung parenchyma of persons occupationally exposed to asbestos commonly showed the presence of other fiber types, especially amosite and crocidolite, at very much higher concentrations and greater fiber length. Any chrysotile present would usually be in fiber bundle form, with both fibers and fibrils > 5 microns in length. Comparison of the lung fiber content of occupationally exposed persons with that of the general population showed marked qualitative and quantitative differences. Fibers are durable, and are retained in a range of concentrations. Their length and dose, among other factors, which control their biological potential are different in the two populations; the risk factors for chrysotile-induced disease are not the same.

In plain English

The authors used transmission electron microscopy to count chrysotile asbestos in autopsy lung tissue from 126 people chosen from 3,000 who died at three New York City hospitals in 1966 to 1968. Most were judged probably not occupationally exposed, based on job history and lung asbestos body counts. Others included pipe-coverers, shipyard workers and construction workers. Some chrysotile was found in 124 of 126 lungs. Using a cutoff about three times the laboratory background level, 64 of 126 cases (50.8%) counted as positive, at 1.8 to 15.7 million fibers per gram of dry lung tissue. Only 52 of 9,256 chrysotile fibers seen (0.56%) were longer than 5 micrometers. In non-occupationally exposed people, nearly all were short fibrils under 1 micrometer. Apparently occupationally exposed people tended to have more of the longer chrysotile. Presumed amphibole fibers over 5 micrometers long appeared only in occupationally exposed people. The highest chrysotile levels did not correlate with asbestos body counts or with occupation. The authors concluded that chrysotile is retained in lungs. Citing their earlier data on exposed workers, they also concluded that the general population is not at the same risk as occupationally 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: Autopsy lung tissue (lung burden) study: lung tissue was chemically digested and the recovered fibers were counted by transmission electron microscopy
• Who was studied: 126 autopsy cases chosen from 3,000 people who died at three New York City hospitals (Mount Sinai Hospital, Veterans Administration Hospital in the Bronx, Elmhurst General Hospital) from 1966 to 1968. Cases were selected on the basis of asbestos body content, occupation and personal history. By asbestos bodies found: 32 had 0, 57 had 1 to 4, 18 had 5 to 14, and 19 had 15 or more.
• Exposure: Chrysotile fibers and fibrils in lung tissue, compared across groups defined by asbestos body counts. Most cases were judged probably not occupationally exposed. The 19 people with 15 or more asbestos bodies were all men, in jobs such as pipe-coverers, shipyard workers, plasterers and construction workers.
• Main results:
  • Of the 126 cases, 107 were judged probably non-occupationally exposed, based on occupational history and the asbestos body content of the lung.
  • Some chrysotile was found in the lungs of 124 of the 126 people.
  • With a cutoff of 27 fibrils (about three times the background of 9 fibrils), 64 of 126 cases (50.8%) were statistically positive.
  • The 64 positive cases had 1.8 to 15.7 x 10^6 chrysotile fibers per gram of dry lung tissue. The remaining 62 cases ranged from below the detection limit (0.064 x 10^6) to 1.73 x 10^6 fibers per gram.
  • Across all cases, only 52 of 9,256 chrysotile fibers or fibrils observed (0.56%) were longer than 5 micrometers.
  • In nonoccupationally exposed persons, virtually all chrysotile was short fibrils, most under 1 micrometer, most often 0.2 to 0.5 micrometers long.
  • There was a trend suggesting that lungs of individuals with apparent occupational exposure contained more chrysotile 1 to 5 micrometers and over 5 micrometers long.
  • The highest chrysotile levels did not correlate with asbestos body content or with occupation.
  • Four of the six cases with more than 99 asbestos bodies had almost no chrysotile in their tissues.
  • Fibers longer than 5 micrometers, presumed to be amphibole based on their shape and diffraction character, were found only in occupationally exposed individuals.
  • The authors interpreted the presence of chrysotile in lung tissue as showing durability, retention and biopersistence.
• The authors' conclusion: The authors concluded that chrysotile is retained in human lungs. In the general population it is mainly trace amounts of short fibrils. They compared this with their earlier reported data on asbestos-exposed persons, where doses were higher and long fibers more common. Because fiber length and dose affect risk, the authors concluded that the general population is not at the same risk as occupationally exposed people.
• Limitations the authors state:
  • Background levels varied between the two tissue sets, so the highest background value, from a 1971 study, was applied to all cases.
  • Some cases counted below background included short fibers rather than fibrils, which the authors said suggested real exposure.
  • Amphibole fibers were presumably present but could not be identified.
  • Chrysotile elimination from the lung was assumed to have occurred, but its extent could only be estimated.

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, biopersistence, Autopsy, Occupational History, Asbestos Body Formation, Fibril, Amphibole Group, Parenchyma.

Related studies

• A biopersistence study following exposure to chrysotile asbestos alone or in combination with fine particles — D.M. Bernstein, K. Donaldson, et al. (2008)
• Fiber size and number in workers exposed to processed chrysotile asbestos, chrysotile miners, and the general population — A. Churg, B. Wiggs (1986)
• The biopersistence of Canadian chrysotile asbestos following inhalation: final results through 1 year after cessation of exposure — D. Bernstein, R. Rogers, et al. (2005)
• The biopersistence of Canadian chrysotile asbestos following inhalation — D.M. Bernstein, R. Rogers, et al. (2003)
• Continued controversy on chrysotile biopersistence — K. Donaldson, G. Oberdörster (2011)
• Prevalence of pleural calcification in persons exposed to asbestos dust, and in the general population in the same district — M. Navrátil, F. Trippé (1972)

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