An update of cancer mortality among chrysotile asbestos miners in Balangero, northern Italy

Our plain-English summary of An update of cancer mortality among chrysotile asbestos miners in Balangero, northern Italy, by G. Piolatto, E. Negri, C. La Vecchia, et al (British Journal of Industrial Medicine, 1990).

The study

• Authors: G. Piolatto, E. Negri, C. La Vecchia, E. Pira, A. Decarli, J. Peto
• Journal: British Journal of Industrial Medicine
• Published: 1990;47(12):810-4
• Cited by: 87 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 003765).

Abstract

The mortality experience of a cohort of chrysotile miners employed since 1946 in Balangero, northern Italy was updated to the end of 1987 giving a total of 427 deaths out of 27,010 man-years at risk. A substantial excess mortality for all causes (standardised mortality ratio (SMR) = 149) was found, mainly because of high rates for some alcohol related deaths (hepatic cirrhosis, accidents). For mortality from cancer, however, the number of observed deaths (82) was close to that expected (76.2). The SMR was raised for oral cancer (SMR 231 based on six deaths), cancer of the larynx (SMR 267 based on eight deaths), and pleura (SMR 667 based on two deaths), although the excess only reached statistical significance for cancer of the larynx. Rates were not increased for lung, stomach, or any other type of cancer. No consistent association was seen with duration or cumulative dust exposure (fibre-years) for oral cancer, but the greatest risks for laryngeal and pleural cancer were in the highest category of duration and degree of exposure to fibres. Although part of the excess mortality from laryngeal cancer is probably attributable to high alcohol consumption in this group of workers, the data suggest that exposure to chrysotile asbestos (or to the fibre balangeroite that accounts for 0.2-0.5% of total mass in the mine) is associated with some, however moderate, excess risk of laryngeal cancer and pleural mesothelioma. The absence of excess mortality from lung cancer in this cohort is difficult to interpret.

In plain English

This study updated deaths to the end of 1987 among 1,058 men who had worked for at least one year between 1946 and 1987 at the chrysotile asbestos mine at Balangero, northern Italy. Deaths were compared with those expected from Italian national rates. There were 427 deaths against 286.3 expected, including 16 from asbestosis. The excess came largely from hepatic cirrhosis and accidents, which the authors linked to alcohol. Cancer deaths overall were close to expected (82 versus 76.2). Laryngeal cancer was significantly raised (eight deaths versus three expected). Oral cancer (six deaths) and pleural cancer (two deaths) were raised but not statistically significant. Lung cancer showed no significant excess (22 deaths versus 19.9 expected), though the data were compatible with a higher risk. Laryngeal and pleural cancer risks were highest among the longest-employed and most heavily exposed workers. The authors concluded that the data suggest chrysotile, or the mine's fibre balangeroite, is associated with a moderate excess risk of laryngeal cancer and pleural mesothelioma, but that cancer deaths were too few for definite conclusions. They added that alcohol probably explains part of the laryngeal excess.

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: Retrospective (historical) cohort mortality study, an update of an earlier report. Observed deaths were compared with numbers expected from Italian national death rates (standardised mortality ratios, SMRs).
• Who was studied: 1058 men who had worked for at least one year between 1946 and 1987 at the Balangero chrysotile mine near Turin, northern Italy (the methods call it "the factory"). 36 men (3%) who could not be traced were excluded. Follow-up ran from 1 January 1946 to 31 December 1987, giving 427 deaths in 27 010 man-years.
• Exposure: Chrysotile asbestos mining. Cumulative dose of inhaled fibres was estimated in fibre-years, from measurements made from 1969 onwards and from artificially re-created working conditions for earlier periods. Samples of the mine's chrysotile showed no fibrous amphiboles at detectable concentrations. A fibrous silicate, balangeroite, made up 0.2 to 0.5% of the total mass of the chrysotile sold from the mine.
• Main results:
  • Whole cohort, all causes of death: 427 observed versus 286.3 expected deaths (SMR 149).
  • Whole cohort, all cancers: 82 observed versus 76.2 expected deaths. The SMR for total cancer mortality was 108 (95% confidence interval 86 to 135).
  • Laryngeal cancer was the only cancer with a statistically significant excess: eight observed versus three expected deaths (SMR 267, p less than 0.05).
  • Oral cancer had an SMR of 231 based on six deaths, and pleural cancer an SMR of 667 based on two deaths. Neither excess was statistically significant.
  • No significant excess was found in mortality from lung cancer: 22 observed versus 19.9 expected deaths (Table 1). The authors wrote that lung, stomach and other cancers were not increased.
  • The authors noted that the lung cancer results were still compatible with a raised risk. The upper 95% confidence limit of the lung cancer SMR was 167, and the true risk may be somewhat higher because of how expected deaths were computed.
  • Laryngeal and pleural cancer risks were highest in workers with the longest duration of exposure (over 20 years): five observed versus 1.1 expected for larynx, and two observed versus 0.2 expected for pleura. Neither showed a statistically significant trend with increasing duration. No association with duration was found for oral cancer.
  • The two pleural cancer deaths were in the highest categories of cumulative dust exposure. For laryngeal cancer, a trend towards greater risk with increasing cumulative dust exposure approached significance (p = 0.05, one sided).
  • For laryngeal cancer the SMR was 158 for less than 20 years of exposure and 456 for longer exposure. For hepatic cirrhosis the SMR was higher with short exposure (343) than with long exposure (204).
  • There were 16 deaths from asbestosis. Deaths from accidents were 47 observed versus 24.3 expected, and from hepatic cirrhosis 45 observed versus 15.3 expected (Table 2). The SMRs for cirrhosis and accidents were highest in the workers with the shortest employment.
  • Among men with cumulative exposure above 400 fibre-ml-years, a dose-risk estimate proposed by Doll and Peto would predict over 35 lung cancer cases. Only 10 were found.
• The authors' conclusion: The authors concluded that the data suggest that exposure to chrysotile asbestos, or to the fibre balangeroite, is associated with some, however moderate, excess risk of laryngeal cancer and pleural mesothelioma. They wrote that some excess of laryngeal and pleural cancer may be related to occupational exposure, but that there were too few cancer deaths to draw definite conclusions. They could not rule out a contribution from balangeroite to the two mesothelioma cases. They considered it conceivable that at least part of the laryngeal cancer excess is due to high alcohol consumption, and they found the absence of excess lung cancer mortality difficult to interpret.
• Limitations the authors state:
  • The number of cancer deaths was still too limited to draw definite conclusions.
  • National rates were used to compute expected deaths, so SMRs for alcohol-related diseases are probably slightly overestimated. The province of Turin had higher rates of oral cancer, laryngeal cancer and cirrhosis than Italy as a whole.
  • For laryngeal cancer, age at first exposure and time since first and last exposure are closely interrelated. With only eight deaths, the authors could not tell which of these factors, if any, mattered most.
  • Death rates from the late 1950s were applied to 1946-54. Because lung cancer rates in the late 1940s were lower, the lung cancer risk in the cohort may be somewhat underestimated.
  • The unusual ratio of asbestosis to lung cancer may be partly explained by overdiagnosis of asbestosis.

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Balangero mine, Balangero, about 20 km north of Turin, Piedmont

All asbestos mines

Topics

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

Medical terms in this study, explained in our Lexicon: Chrysotile, Laryngeal Cancer, Pleura, Statistical Significance, Balangeroite, Pleural Mesothelioma, Lung Cancer.

Related studies

• An update of cancer mortality among chrysotile asbestos miners in Balangero, northern Italy — R. Calisti, P. De Giuli, et al. (1992)
• Mortality of Talc Miners and Millers From Val Chisone, Northern Italy: An Updated Cohort Study — E. Pira, M. Coggiola, et al. (2017)
• An update of a mortality study of talc miners and millers in Italy — M. Coggiola, D. Bosio, et al. (2003)
• Mortality from cancer and other causes in the Balangero cohort of chrysotile asbestos miners — E. Pira, C. Pelucchi, et al. (2009)
• Mortality and mesothelioma incidence among chrysotile asbestos miners in Balangero, Italy: A cohort study — D. Ferrante, D. Mirabelli, et al. (2020)
• Re Ferrante et al (2020). Mortality and mesothelioma incidence among chrysotile asbestos miners in Balangero, Italy: A cohort study — J. Schüz, H. Kromhout (2020)

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