First and subsequent asbestos exposures in relation to mesothelioma and lung cancer mortality

Our plain-English summary of First and subsequent asbestos exposures in relation to mesothelioma and lung cancer mortality, by E. Pira, C. Pelucchi, P.G. Piolatto, et al (British Journal of Cancer, 2007).

The study

• Authors: E. Pira, C. Pelucchi, P.G. Piolatto, E. Negri, G. Discalzi, C. La Vecchia
• Journal: British Journal of Cancer
• Published: 2007;97(9):1300-4
• Type of article: Meta-analysis
• Cited by: 37 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

We analysed data from a cohort of 1966 subjects (889 men and 1,077 women) employed by an Italian asbestos (mainly textile) company in the period 1946-1984, who were followed-up to 2004. A total of 62,025 person-years of observation were recorded. We computed standardised mortality ratios (SMR) for all causes and selected cancer sites using national death rates for each 5-year calendar period and age group. There were 68 deaths from mesothelioma (25 men and 43 women, 39 pleural and 29 peritoneal) vs 1.6 expected (SMR=4,159), and 109 from lung cancer vs 35.1 expected (SMR=310). The SMRs of pleural/peritoneal cancer were 6661 for subjects exposed only before 30 years of age, 8,019 for those first exposed before 30 and still employed at 30-39 years of age and 5,786 for those first exposed before 30 and still employed at 40 or more years of age. The corresponding SMRs for lung cancer were 227, 446 and 562. The SMR of mesothelioma was strongly related to time since first exposure. The SMR of lung cancer, but not of mesothelioma, appeared to be related to subsequent exposures.

In plain English

This cohort study followed 1,966 people (889 men, 1,077 women) who worked at least one month between 1946 and 1984 in an Italian asbestos textile factory that used various asbestos types, including crocidolite. Deaths to the end of 2004 (or to age 80, if earlier) were compared with those expected from national death rates, as standardised mortality ratios (SMRs; 100 means as many deaths as expected). There were 68 pleural or peritoneal cancer deaths against 1.6 expected, and 109 lung cancer deaths against 35.1 expected. Mesothelioma risk was higher with younger first employment and after 15 years since first employment. Lung cancer, but not mesothelioma, rose with duration of employment. Among workers first employed before 30, pleural/peritoneal cancer SMRs were 6661 if employed only before 30, 8019 if still employed at 30 to 39, and 5786 if still employed at 40 or older. For lung cancer the figures were 227, 446 and 562. The authors concluded that pleural/peritoneal cancer SMRs did not increase in workers with both earlier and later exposures, whereas later exposures appreciably increased lung cancer relative risk. They noted limits of SMRs and that some workers had earlier asbestos exposure elsewhere.

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 cohort mortality study (extended follow-up of an earlier analysis), using standardised mortality ratios based on national death rates
• Who was studied: 1966 people (889 males, 1077 females) who worked at least 1 month in a major asbestos textile factory in Italy between 1946 and 1984. They were followed to 31 December 2004 or to age 80 if that came earlier, for 62 025 person-years.
• Exposure: Employment in an asbestos textile factory where various types of asbestos were used, including crocidolite. Exposure was analysed by age at first and last employment, duration of employment, and time since first and last employment.
• Main results:
  • Across the whole cohort there were 730 deaths from all causes, compared with 424.5 expected.
  • 68 people (25 men and 43 women) died from pleural or peritoneal cancer, compared with 1.6 expected. The SMR was 4623 for pleural cancer and 3665 for peritoneal cancer.
  • There were 109 lung cancer deaths against 35.1 expected. The lung cancer SMR changed only modestly, from 282 at the earlier follow-up to 310 in this update.
  • SMRs for pleural, peritoneal and lung cancer were higher in women than in men. The authors attribute this to women's lower baseline rates.
  • The authors also found increased mortality from ovarian and liver cancers, and an excess of laryngeal cancer. They suggest that misdiagnosis may explain the ovarian and liver excesses.
  • The pleural/peritoneal cancer SMR was 7968 for workers first employed before age 25 and 2085 for those first employed at 35 or older.
  • SMRs for both pleural/peritoneal cancer and lung cancer were higher after 15 years since first employment. The overall mesothelioma SMR rose from 3139 in 1946 to 1996 to 6792 in 1997 to 2004.
  • Lung cancer risk increased with duration of employment; mesothelioma risk did not.
  • Among all subjects first employed before age 30, pleural/peritoneal cancer SMRs were 6661 for those employed only before 30, 8019 for those still employed at 30 to 39, and 5786 for those still employed at 40 or older.
  • In the same groups, lung cancer SMRs increased from 227 (employed only before 30) to 446 (still employed at 30 to 39) and to 562 (still employed at 40 or older).
  • Using local Turin death rates for 1980 to 2000 instead of national rates, pleural cancer SMRs were lower but still high: 2039 in men, 6431 in women and 3414 overall.
• The authors' conclusion: The authors concluded that for pleural and peritoneal cancers the SMR did not increase in people with both earlier and later asbestos exposures, whereas for lung cancer subsequent exposures led to appreciable increases in relative risk.
• Limitations the authors state:
  • The validity of SMRs as a risk indicator is a possible source of bias.
  • Direct standardisation, generally preferable, was not used because there were relatively few mesothelioma deaths (68).
  • Cohort studies may underestimate the true risk when SMRs are large.
  • In 1968 a nearby asbestos factory was acquired and some workers moved between plants. Information on these workers' previous exposures was lacking, which might explain inconsistent results.
  • No occupational history was taken. Some workers had previous asbestos exposure in other jobs, so mesothelioma risk for a late age at first exposure was overestimated.

Topics

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

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Mesothelioma, Lung Cancer.

Related studies

• Cancer mortality in a cohort of asbestos textile workers — E. Pira, C. Pelucchi, et al. (2005)
• Mortality from cancer and other causes in the Balangero cohort of chrysotile asbestos miners — E. Pira, C. Pelucchi, et al. (2009)
• An update of a mortality study of talc miners and millers in Italy — M. Coggiola, D. Bosio, et al. (2003)
• An update of cancer mortality among chrysotile asbestos miners in Balangero, northern Italy — G. Piolatto, E. Negri, et al. (1990)
• Mesothelioma risk after 40 years since first exposure to asbestos: a pooled analysis — A. Reid, N.H. de Klerk, et al. (2014)
• Mortality of Talc Miners and Millers From Val Chisone, Northern Italy: An Updated Cohort Study — E. Pira, M. Coggiola, et al. (2017)

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