Clinical Survey of Chrysotile Asbestos Miners and Millers in Newfoundland - 1976

Our plain-English summary of Clinical Survey of Chrysotile Asbestos Miners and Millers in Newfoundland - 1976, by Irving J. Selikoff (1977).

The study

• Author: Irving J. Selikoff
• Published: Memorandum to the National Institute of Environmental Health Sciences, December 7, 1977; Environmental Sciences Laboratory, Mount Sinai School of Medicine of the City University of New York
• Type of article: Report
• Our copy: from Johns-Manville's own medical library, J-M no. 004893. The article is still under copyright, so we describe it here rather than post it.

In plain English

This report described a medical survey at the Advocate Mines chrysotile asbestos mine and mill in Baie Verte, Newfoundland, which opened around 1963. In June 1976, all current employees (about 500) were invited for chest x-rays, breathing tests, blood tests and other examinations, and 485 men and women took part. Fifty of 485 (10%) had one or more x-ray changes commonly associated with asbestos exposure. Most of these changes were in the lung tissue, and two-thirds of the lung-tissue changes were in the lowest grade. Abnormalities were more common with longer employment, rising from 9 of 168 (5.4%) workers with under 5 years to 29 of 200 (15%) with 10 or more years. They were also more common in higher job-exposure categories; workers in the highest category with over 10 years had 19%. Only 6 of 474 adequate breathing tests showed restrictive impairment. The changes found were not enough to cause disability or serious symptoms in anyone examined. The author suggested a dose-response relationship and said the changes raised the question of a future increased risk of asbestos-associated cancer, mainly of the lung, which this survey could not predict.

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 clinical survey (one-time medical examinations of current employees); the report also opens with background tables from the laboratory's other studies, which are not part of this survey
• Who was studied: Current employees of Advocate Mines, a chrysotile mine and mill at Baie Verte, Newfoundland, operating since about 1963. About 500 were invited to examinations held June 14-18, 1976, at the Baie Verte Peninsula Health Centre, and 485 men and women were examined.
• Exposure: Chrysotile asbestos mining and milling. Jobs were grouped into four relative exposure categories, from category 1 (least, e.g. storesman, toolroom clerk) to category 4 (highest, e.g. primary crusher, mill operator, tailings helper). Duration of employment was also examined. Dust measurements had not yet been used to calculate individual exposure indices.
• Main results:
  • Of the 485 people examined, 50 (10%) had one or more x-ray abnormalities commonly associated with asbestos exposure; changes in the lung tissue (parenchyma) predominated, and only 3 individuals had both lung-tissue and pleural abnormalities
  • The lung-tissue abnormalities tended to be very early; two-thirds were classified in the lowest category (1/0)
  • Pleural findings: pleural calcification in 3 individuals, lateral diffuse wall thickening in 8, and discrete plaques on the diaphragms in 6
  • Abnormal x-rays increased with duration of employment: 9 of 168 (5.4%) with less than 5 years, 12 of 117 (10%) with 5-9 years, and 29 of 200 (15%) with 10 or more years. Lung-tissue abnormalities rose from 3% to 11.5%.
  • By exposure category, any abnormality was found in 3 of 44 (7%) in category 1, 13 of 142 (9%) in category 2, 21 of 191 (11%) in category 3, and 13 of 108 (12%) in category 4. The highest prevalence, 19%, was among those with more than 10 years in exposure category 4.
  • 111 participants had worked for 1 or more months in other mines in the area; for the x-ray abnormalities reported, there was no detectable contribution of this other mining experience
  • Of 46 individuals who had also worked on building the mine and mill (from as early as 1959), the group of 42 who helped build it and worked there continuously had the highest prevalence of abnormalities (31%)
  • Only 6 of 474 adequate breathing tests showed any evidence of restrictive impairment; as a whole, the workers performed better than predicted (mean forced vital capacity 106% of predicted)
  • The extent of the lung changes was not sufficient, at the time, to produce disability or serious symptoms in any of those examined
• The authors' conclusion: The author concluded that a dose-response relationship was suggested when exposure category and duration of employment were considered. The author also said that any asbestos-related x-ray changes showed exposure sufficient to cause a lung reaction and raised the serious question of an increased future risk of asbestos-associated cancers, principally of the lung, the extent of which this survey could not predict.
• Limitations the authors state:
  • Length of exposure and time since first exposure had not been long enough for clinically evident abnormalities to develop, and the percentage with abnormalities was expected to increase with time
  • Measured dust levels had not yet been incorporated; only relative exposure categories were used
  • Variability among x-ray readers had not yet been analyzed; this report used the consensus reading of five Mount Sinai readers
  • The future cancer risk could not be predicted from this survey, and reliable data were not expected for 10 or more years

Topics

Medical terms in this study, explained in our Lexicon: Chrysotile, Chest X-Ray, Asbestos Exposure, Dose-response relationship.

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