Pulmonary Function and Roentgenographic Changes in Granite Dust Exposure

Our plain-English summary of Pulmonary Function and Roentgenographic Changes in Granite Dust Exposure, by G.P. Theriault, J.M. Peters, W.M. Johnson (1974).

The study

• Authors: G.P. Theriault, J.M. Peters, W.M. Johnson
• Published: Archive Environmental Health, Volume 28. January 1974
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library. The article is still under copyright, so we describe it here rather than post it.

In plain English

This study concerned granite dust, not asbestos. The authors studied 792 Vermont granite shed workers, about 90% of active workers aged 25 to 65 in fall 1971; eight poor-quality chest X-rays were rejected, leaving 784 films. Their lung function and lifetime dust exposure were known from an earlier study. Films were classified with the UICC/Cincinnati system: 551 were read as normal and 233 as showing opacities compatible with pneumoconiosis. Workers with abnormal films averaged 43 dust-years of exposure, against 19 for those with normal films, and had smoked longer; both differences were reported as significant. Among rounded opacities, dust exposure rose with opacity size and profusion. Irregular opacities were more closely associated with smoking than with dust exposure. About 30% of workers had opacities at exposures up to 35 dust-years, and the authors estimated that 50% did at 46 dust-years. After adjustment for age, height and smoking, only forced vital capacity remained significantly lower with abnormal films, and it was lower at higher profusion. The authors concluded that lung function tests detect early dust effects in groups of workers better than X-rays do.

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: Cross-sectional study comparing chest X-ray classification with lifetime dust exposure, smoking and lung function in a working population
• Who was studied: 792 granite shed workers in Vermont, about 90% of the active workers aged 25 to 65, studied in fall 1971. Eight poor-quality films were rejected, leaving 784 chest X-rays.
• Exposure: Lifetime exposure to granite dust (and quartz), measured in dust-years. One dust-year is one year of exposure to the average dust concentration in the granite sheds, 523 micrograms per cubic meter of granite dust. Smoking history (years smoked) was also studied.
• Main results:
  • Of the 784 films, 551 were read as normal and 233 as abnormal (opacities compatible with pneumoconiosis).
  • Workers with abnormal films had averaged 43 dust-years of exposure, compared with 19 dust-years for workers with normal films (Table 1). The authors reported this difference as highly significant (P less than .01) and stated it could not be accounted for by the age difference between the groups.
  • Among workers with rounded opacities, dust exposure increased with opacity size and profusion. The average was 25 dust-years for opacity p, profusion 1, and 79 dust-years for opacity q, profusion 2. For irregular opacities there was no such trend: dust exposure increased from s to t, but it was not related to profusion.
  • Workers with abnormal films had smoked longer than those with normal films (P less than .01). Smoking increased across irregular opacities (from s to t and from profusion 1 to 2), which the authors took to suggest that smoking and dust account for different opacities.
  • The share of workers with opacities stayed at a plateau of around 30% for exposures from 0 to 35 dust-years and then rose. The exposure at which 50% of active workers had opacities was estimated at 46 dust-years.
  • After standardizing for age, height and smoking, only forced vital capacity (FVC) remained significantly lower in workers with abnormal films. Total lung capacity, residual volume and the FEV1/FVC ratio became similar in the two groups.
  • Among workers with abnormal films, after adjustment, FVC differed significantly only by profusion: workers with profusion 2 had lower FVC than those with profusion 1. There was no significant FVC difference by opacity shape or size.
  • Among workers with abnormal films, after adjustment, residual volume increased with opacity size (p,s to q,t) and with profusion (1 to 2). Total lung capacity did not vary with opacity shape, size or profusion.
• The authors' conclusion: The authors concluded that, in groups of workers, early detection of dust effects is better accomplished by pulmonary function tests than by chest X-rays. They also concluded that rounded opacities increase in size and number with dust exposure, while smoking produces an increase in irregular opacities.
• Limitations the authors state:
  • Because of technical restraints, analysis of covariance was performed on unweighted means, which decreased the sensitivity of the test.
  • Few workers were classified with large opacities (r, u) or profusion 3, so the analysis was limited to sizes p,s and q,t and to profusion 1 and 2.
  • The comparison between the X-ray dose-response curve and the lung-function dose-response curve from a related study was weakened because the X-ray curve does not start at zero (it begins at a plateau of about 30%).

Topics

Medical terms in this study, explained in our Lexicon: Chest X-Ray, UICC, Pneumoconiosis.

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