Urinary fibres in occupational exposure to asbestos

Our plain-English summary of Urinary fibres in occupational exposure to asbestos, by M.P. Guillemin, G. Litzistorf, P.A. Buffat (The Annals of Occupational Hygiene, 1989).

The study

• Authors: M.P. Guillemin, G. Litzistorf, P.A. Buffat
• Journal: The Annals of Occupational Hygiene
• Published: 1989;33(2):219-33
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Urine samples from 10 workers from an asbestos cement factory and from a control group of 10 workers from a foundry, were obtained; drastic precautions were taken to avoid contamination. Each urinary mineral fibre was sized and identified by transmission electron microscopy. Results show that contamination problems encountered by other authors have been overcome and that the workers exposed to chrysotile appear to excrete more chrysotile fibres, but that this difference is not statistically significant. Possibly only a few of the exposed workers are significantly exposed to asbestos, the overall exposure level being very low. The degradability of chrysotile fibres in biological fluids or the retention of fibres in some organ could explain the lack of apparent correlation between exposure and urinary concentration. Unexpectedly high concentrations of crocidolite fibres of unknown origin were detected in both groups of workers.

In plain English

This study compared mineral fibres in the urine of 10 workers from an asbestos cement factory, where chrysotile was the only asbestos type processed, with 10 foundry workers the authors assumed were not exposed to asbestos. The authors took strict precautions against contamination and counted, sized and identified each fibre by transmission electron microscopy. Two exposed and three control samples could not be processed, which left 8 and 7. All blanks were below the detection limit. Mean urinary chrysotile was 909 ±788 fibres per ml in the exposed workers and 480 ±232 in the controls, about twice as high, but the difference was not statistically significant. Both groups had more crocidolite than chrysotile in their urine, and its origin was unknown. All asbestos fibres found were short. Urinary levels showed no relationship with airborne exposure, which the authors described as low. The authors noted the small number of samples, large differences between individuals and the lack of personal air sampling. They concluded that monitoring asbestos-exposed workers through urinary fibre counts is far from promising.

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: Comparison of urinary fibre concentrations in an exposed worker group and an unexposed control group, using transmission electron microscopy with precautions against contamination
• Who was studied: 10 workers from an asbestos cement factory, selected by the factory management (mean age 36.3, mean 10.8 years in the factory), and 10 control workers from a foundry in a city about 20 km away (mean age 48.9, mean 16.6 years in the factory). Usable urine samples came from 8 exposed and 7 control workers. The article does not give study dates.
• Exposure: Chrysotile in asbestos cement manufacture (plate manufacture, dispatching, workshop and storage, manual shaping). Management's stationary air sampling, analysed by phase contrast microscopy, gave airborne concentrations of less than 0.1 to 0.1 fibres per ml in most areas and 0.25 and 0.2 fibres per ml in manual shaping.
• Main results:
  • All blanks were below the detection limit, which the authors took to mean that no contamination had occurred.
  • Urinary chrysotile in exposed workers (8 samples) was about twice that in controls (7 samples): median 785 versus 457 fibres per ml, and mean 909 ±788 versus 480 ±232 fibres per ml. The difference was not statistically significant.
  • In both groups the urinary concentration of crocidolite was higher than that of chrysotile (median 1130 fibres per ml in exposed workers and 1280 in controls; no significant difference between groups). The origin of the crocidolite was unknown.
  • The data showed no relationship between airborne exposure and urinary concentration. The worker with the highest apparent exposure (E8, manual shaping) did not excrete more fibres than the others.
  • All asbestos fibres found in urine were short. No chrysotile fibre was longer than 2.0 micrometres and the longest crocidolite fibre was 2.5 micrometres. There was no marked difference in fibre size between the groups, apart from slightly longer chrysotile fibres in the controls.
  • Two urine samples from the exposed group and three from the control group could not be processed.
• The authors' conclusion: The authors concluded that biological monitoring of asbestos-exposed workers by analysing urinary fibre concentrations is far from promising. They added that its cost and the precautions needed against contamination make the approach unattractive.
• Limitations the authors state:
  • The study included no personal sampling of external exposure. The available air figures, from stationary sampling and optical microscopy, covered only fibres longer than 5 micrometres.
  • Large differences between individuals in the exposed group and the low number of samples limited statistical significance.
  • The overall exposure was low and varied between workers, so possibly only a few workers were significantly exposed.
  • A rather high proportion of urine samples could not be processed, which the authors called a disadvantage of the method.
  • Urinary fibre concentrations could not be corrected for creatinine because the added hydrogen peroxide interferes with creatinine analysis.
  • Occasional asbestos exposure among the control workers could not be excluded.

Topics

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Asbestos-Cement, Transmission Electron Microscopy (TEM), Chrysotile, Crocidolite.

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