Respiratory Morbidity of Workers Exposed to Wollastonite Through Mining and Milling

Our plain-English summary of Respiratory Morbidity of Workers Exposed to Wollastonite Through Mining and Milling, by D.M. Shasby, M. Petersen, T. Hodous, et al (1979).

The study

• Authors: D.M. Shasby, M. Petersen, T. Hodous, B. Boehlecke, J.A. Merchant
• Published: Dusts and Disease (1979)
• Type of article: Conference paper
• 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, by researchers at the National Institute for Occupational Safety and Health (NIOSH), examined the lungs and breathing of men who mined and milled wollastonite. Wollastonite is a fibrous calcium silicate used as a substitute for asbestos. The workplace was the only U.S. deposit being mined, which had operated since 1952. The analysis included 104 men, 72% of all men with at least 1 year of exposure, and their average exposure was 9.2 years. Air samples counted 0.3 fibers/cc in the mine and 23.3 fibers/cc in the mill. Breathing capacity (FVC) and total lung capacity showed no significant correlation with an index of exposure. Airflow obstruction appeared more often among men with 15 or more years of exposure, but the authors reported that this increase was not statistically significant and that the apparent trend was explained by age. Four men had small rounded opacities (category 1) on chest x-rays, and no irregular opacities or pleural plaques were noted. The authors concluded that chronic bronchitis symptoms were more common than in non-dusty jobs, possibly from a non-specific dust effect. The scanned text is badly damaged and ends mid-sentence.

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 medical survey of current and former workers (questionnaire, lung function tests, chest x-rays, chest examination), with environmental dust sampling
• Who was studied: Workers at the only wollastonite mine and mill operating in the U.S. (in operation since 1952). The analysis included 104 men, 72% of all men with at least 1 year of exposure since 1952. This total included current workers examined on site and ex-workers, some by telephone questionnaire only. Mean duration of exposure was 9.2 years, and 36% had 15 or more years of exposure.
• Exposure: Wollastonite (fibrous monocalcium silicate) dust from mining and milling. The median fiber diameter was 0.22 micrometers and the median length 2.5 micrometers. Phase contrast fiber counts were 0.3 fibers/cc in the mine and 23.3 fibers/cc in the mill. These counts were combined with work history to give an exposure index.
• Main results:
  • Forced vital capacity (FVC) and total lung capacity estimated from the chest x-ray were not significantly correlated with the exposure index.
  • One worker had an FVC more than 2 standard errors below the normal regression line. His FVC had fallen by only 10 cc since 1964, and his chest x-ray was normal.
  • Obstructive lung impairment (by FEV1/FVC ratio) was found in the following groups:
• Smokers and ex-smokers: 15% of 40 men with less than 15 years of exposure, and 29% of 24 men with 15 or more years.
• Non-smokers: 8% of 13 men with less than 15 years, and 25% of 4 men with 15 or more years.
  The higher figures are marked with a footnoted p-value that the scan prints in garbled form.
  • The authors reported that obstructive impairment did not increase significantly with increasing exposure, and that the apparent trend was explained by age. The sentence is partly garbled in the scan.
  • Only 1 worker had a diffusing capacity for carbon monoxide below 80% of predicted. The authors noted he had a blood condition that may alter this test.
  • Four men had chest x-rays showing category 1 small rounded opacities. The table classifies all positive x-rays as 1q; the text's 'type g' is a scanning error.
  • One worker had grade 1 pleural thickening, but he had a history of chest trauma and three prior episodes of pneumonia.
  • No irregular opacities or pleural plaques were noted on chest x-rays.
• The authors' conclusion: The authors concluded that chronic bronchitis symptoms were more common in the study group than in non-dusty occupations, possibly due to industrial bronchitis from a non-specific dust effect. They also stated there were no findings of restrictive lung disease, but the sentence is cut off.

Topics

Medical terms in this study, explained in our Lexicon: Wollastonite, NIOSH, Silicate, Total Lung Capacity (TLC), Obstructive Lung Disease, Chest X-Ray, Pleural Plaques.

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