Enclosure 4 - Epidemiology of Asbestos Related Diseases

Our plain-English summary of Enclosure 4 - Epidemiology of Asbestos Related Diseases, by L.K. Noro (1970).

The study

• Author: L.K. Noro
• Published: 1970
• 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 paper by L.K. Noro, of Helsinki's Institute of Occupational Health, was a review, not a new study. The author summarized recent knowledge on asbestos-related diseases, mainly from conferences in Johannesburg, Turin, New York and Dresden. Citing other studies, the author reported lung cancer 2-10 times more frequent among asbestos workers than in the general population. The author quoted Selikoff's estimate that smoking asbestos workers have 90 times the lung cancer death risk of men who do neither. In Finland's asbestos area, where the asbestos was anthophyllite, about 1,300 pleural calcifications had been found on X-rays but only one so-called pleural mesothelioma. One recent mesothelioma case was also found among Finnish workers; that worker had also been exposed to types other than anthophyllite. Autopsies found pleural plaques in about 30-40% of Finnish adults. The author noted asbestosis becoming less common as dust control improved. Without uniform study standards, the author stated, asbestosis incidence could not be compared between countries. The author concluded that with continued dust control, occupational asbestosis would gradually disappear as a cause of death or disability.

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: Review: a summary of recent knowledge on the epidemiology of asbestos-related diseases, drawn mainly from recent international conferences and meetings
• Who was studied: No new population was studied. The review drew on published work and presentations from conferences in Johannesburg (1969), Turin, New York (1964) and Dresden (1968), and on two meetings at Antigua (1965 and 1967). It reported on asbestos workers and general populations in several countries, especially Finland.
• Exposure: Occupational and non-occupational exposure to asbestos dust. The author stressed that this was usually mixed dust containing other materials such as talc. In Finland the asbestos type was anthophyllite.
• Main results:
  • The author reported that in Finland about 20,000 tons of asbestos was used each year and about 1,200 workers were exposed.
  • Citing several epidemiological studies from many countries, the author reported that lung cancer was 2-10 times more frequent among asbestos workers than among the general population.
  • The author quoted Selikoff: an asbestos worker who smokes cigarettes has 90 times the risk of dying of lung cancer compared with a man who neither works with asbestos nor smokes cigarettes.
  • In the population living in the asbestos area in Finland, about 1,300 cases of pleural calcification had been diagnosed from X-rays, but only one case of so-called pleural mesothelioma had been found.
  • One case of mesothelioma had also recently been found among workers in Finland. The worker in that case had also been exposed to asbestos types other than anthophyllite.
  • About 30-40% of the overall adult population in Finland showed some kind of pleural plaques at autopsy.
  • Citing Pooley et al., the author reported that the frequency of asbestos (ferruginous) bodies in lungs across 12 centers ranged from 1% (Galway) to 39% (Finland).
  • Citing Gilson, the author reported that on average about 35 years had been needed for workers with some materials to develop mesothelioma of the pleura.
  • Citing Mitchell, the author reported about a 100-fold improvement in dustiness in the U.S.A. from 1936 to 1960. Citing Knox and Smither in England, the author reported that the prevalence of asbestosis had earlier been as high as 81% after 20-24 years of exposure, but was about 3.0% in 1957.
• The authors' conclusion: The author concluded that if improvements in indoor and outdoor dust control continued, occupational asbestosis would step by step disappear as an occupational disease causing death or disability. In the author's view, asbestos dust would become a very minimal health factor for the general population compared with factors such as smoking and air pollution.
• Limitations the authors state:
  • The author stated that the incidence of asbestosis could not be compared between countries because there were no uniform standards for epidemiological studies.
  • The author stated that exact information on the number of exposed workers worldwide was lacking.

Topics

Medical terms in this study, explained in our Lexicon: Epidemiology, Lung Cancer, Anthophyllite, Pleural Calcification, Pleural Mesothelioma, Mesothelioma, Pleural Plaques, Dust Control.

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