Radiographic Survey Of Perlite Workers

Our plain-English summary of Radiographic Survey Of Perlite Workers, by W.C. Cooper (1975).

The study

• Author: W.C. Cooper
• Published: Journal Of Occupational Medicine 17(5):304-307, May (1975)
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library, J-M no. 001124. The article is still under copyright, so we describe it here rather than post it.

In plain English

This study was about perlite, a volcanic glass used in insulation and filters, not asbestos. The author collected chest X-rays of men with over one year of work at ten U.S. plants that mined or expanded perlite. Of 285 eligible current and former workers, films were found for 240. Each man's last readable film was read without knowledge of his work history, and doubtful and positive films were checked by a consulting radiologist. Only three men had positive films. Two had pneumoconiosis; both had earlier long exposure to diatomaceous earth. The third had a history of migratory pneumonitis and was counted as negative for pneumoconiosis. Seven films were finally classed as doubtful, with no correlation to length of exposure. None of the 28 men with 15 or more years in perlite had positive evidence of pneumoconiosis. The author concluded that the results support the position that perlite does not produce pneumoconiosis. The author also noted that no one had been exposed over 25 years, only seven men had worked 20 years or more, and some ores contain quartz. The Perlite Institute funded the study.

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: Radiographic survey: review of existing chest X-ray films of current and former workers in perlite mining and expanding plants
• Who was studied: 285 men (150 current, 135 former workers) who had worked with perlite for more than one year at ten participating U.S. plants. Chest films were obtained for 240 of them. The study was arranged in September 1972, and the men had worked 1 to 23 years in the industry.
• Exposure: Dust from crude perlite ore and expanded perlite. Some crude ores contain up to about 6% crystalline silica (quartz). Exposure measurements were limited: at one mine and mill, six of seven dust counts were above 32 million particles per cubic foot.
• Main results:
  • Of the 240 men with films, three had positive films, and only two of these were classified as pneumoconiosis.
  • Both men with pneumoconiosis had long prior exposure to diatomaceous earth before working with perlite. One had simple and the other complicated diatomite pneumoconiosis.
  • The third positive film was in a man with a history of migratory pneumonitis. It was not interpreted by any observer as pneumoconiosis and was counted among the films negative for pneumoconiosis.
  • Seven films were finally classified as doubtful. They showed no correlation with duration of exposure.
  • None of the 28 men with 15 years or more of work in perlite had positive evidence of pneumoconiosis.
  • Although this was not systematically studied, none of the 150 men with serial films reviewed showed development or activation of pulmonary tuberculosis.
• The authors' conclusion: The author concluded that the results support the position that perlite does not produce pneumoconiosis. Because exposures had lasted no more than 25 years and some ores contain quartz, the author considered it prudent to keep exposures at or below nuisance dust levels and to continue medical surveillance.
• Limitations the authors state:
  • No worker had been exposed for more than 25 years.
  • Only 28 men had worked over 15 years and only seven for 20 years or more.
  • Precise exposure data were not available.
  • Films could not be located for 45 of the 285 men.
  • Exposures to crude ore and to expanded product were combined in the analysis.
  • Job titles alone were of limited use for classifying exposure.
  • Lung function was not studied. The author stated that such studies are needed to supplement the X-ray evidence.

Topics

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

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