Occupational exposure and regional variation of malignant mesothelioma in Norway, 1970-79

Our plain-English summary of Occupational exposure and regional variation of malignant mesothelioma in Norway, 1970-79, by G. Mowé, B. Gylseth (American Journal of Industrial Medicine, 1986).

The study

• Authors: G. Mowé, B. Gylseth
• Journal: American Journal of Industrial Medicine
• Published: 1986;9(4):323-32
• Cited by: 22 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000423).

Abstract

This investigation is based on a study of 117 men and 24 women with malignant mesothelioma registered by the Cancer Registry of Norway, 1970-79. The age-adjusted incidence rate in men for each county varied from 1.7 to 13.3 per million per year. Eighty-two percent of the men revealed possible occupational asbestos exposure. They were evenly distributed between counties with high and low mesothelioma incidence. Only 17% of the women had possible occupational asbestos exposure. Total lung fiber concentration was analyzed with scanning electron microscopy in 65 men and 13 women. The median lung fiber concentration in men was 2.4 million per gram of dried tissue (range less than 0.4-490), in women 1.0 million per gram (range less than 0.4-41), and in male controls less than 0.4 million per gram (range less than 0.4-4.8). The median year of first exposure was 1937 (range 1909-60) for men from counties with a high incidence rate and 1945 (range 1938-59) for men from counties with a low incidence rate. The counties with a high compared to a low incidence rate of malignant mesothelioma, 1970-79, showed an apparent difference in the percentage of population employed in industry in 1946. The regional variation in the incidence of malignant mesothelioma in men is mainly attributable to the proportion of population exposed to asbestos in industry per county prior the 1950s and the time since exposure started.(ABSTRACT TRUNCATED AT 250 WORDS)

In plain English

This study covered the 117 men and 24 women with malignant mesothelioma registered in Norway's Cancer Registry, 1970 to 1979. Most cases (125) were pleural. From records, the authors rated how likely each case's occupational asbestos exposure was. They also analyzed lung tissue fibers in 65 men and 13 women and compared counties. Eighty-two percent of the men, but only 17% of the women, had possible occupational asbestos exposure. Median lung fiber concentration was 2.4 million fibers per gram of dried tissue in men with mesothelioma, versus less than 0.4 million in 28 male controls. Men's age-adjusted county incidence rates reached 13.3 per million per year. The share of exposed cases was similar across counties. However, men from high-incidence counties were first exposed about 10 years earlier, and a larger percentage of those counties' population worked in industry in 1946. The authors said this suggests the regional variation was real, probably reflecting the share of each county's population exposed to asbestos in industry before the 1950s and the time since first exposure. They called their indirect exposure assessment inadequate.

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: Registry-based descriptive study of mesothelioma cases, with retrospective occupational exposure classification, lung fiber analysis by scanning electron microscopy, and county incidence rates
• Who was studied: 117 men and 24 women with malignant mesothelioma registered in Norway, 1970-79 (125 pleural, 14 peritoneal, 2 pericardial); lung fibers analyzed in 65 men and 13 women; 28 male controls who died of cardiovascular diseases
• Exposure: Occupational asbestos exposure estimated from records and classified into four groups (definite, probable, possible, unlikely or unknown); total lung fiber concentration measured by scanning electron microscopy
• Main results:
  • 82% of the men had possible occupational asbestos exposure
  • 8 men (6.8%) were in occupations with definite exposure; 76 men (65%) had definite or probable exposure
  • Only 4 women (17%) had possible occupational asbestos exposure
  • Median lung fiber concentration was 2.4 million per gram of dried tissue in men with mesothelioma (range less than 0.4 to 490), and less than 0.4 million (range less than 0.4 to 4.8) in male controls
  • Median lung fiber concentration in 13 women with mesothelioma was 1 million per gram of dried tissue (range less than 0.4 to 41)
  • Age-adjusted county incidence rates in men ranged up to 13.3 per million per year
  • Exposed cases were evenly distributed between high- and low-incidence counties
  • Men from high-incidence counties were first exposed about 10 years before men from low-incidence counties (median year of first exposure 1937 in high-incidence counties); the difference was statistically significant
  • Percentage of population employed in industry in 1946 was 34.2% to 45.7% in high-incidence counties and 20.5% to 31.2% in low-incidence counties
  • An unexpected cluster of seven farmers was found among men with unlikely or unknown occupational exposure
• The authors' conclusion: The authors wrote that these observations suggest the regional variation in Norway is real and probably reflects the proportion of each county's population exposed to asbestos in industry before the 1950s and the time since first exposure; nonoccupational exposure and nonasbestos agents may be involved in some cases
• Limitations the authors state:
  • Exposure was assessed retrospectively from indirect information, which the authors called inadequate
  • Direct contact with patients or families was not permitted
  • Small county populations mean a few over- or under-reported cases could strongly affect rates
  • Diagnoses were not re-reviewed
  • Information was incomplete for some cases, so asbestos exposure could not be excluded in the unlikely or unknown group, and household exposure in women could not be excluded

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma.

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Malignant Mesothelioma, Cancer Registry, Incidence, Asbestos Exposure, Mesothelioma, Scanning Electron Microscopy (SEM).

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