A historical cohort mortality study among shipyard workers in Genoa, Italy

Our plain-English summary of A historical cohort mortality study among shipyard workers in Genoa, Italy, by R. Puntoni, F. Merlo, L. Borsa, et al (American Journal of Industrial Medicine, 2001).

The study

• Authors: R. Puntoni, F. Merlo, L. Borsa, G. Reggiardo, E. Garrone, M. Ceppi
• Journal: American Journal of Industrial Medicine
• Published: 2001;40(4):363-70
• Cited by: 48 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: A historical cohort mortality study was conducted among 3984 shipyard workers assigned to ship repair, refitting, and construction in the harbor of Genoa, Italy, between 1960 and 1981. These workers were exposed to asbestos fibers, welding fumes and gases, silica dust, polycyclic aromatic hydrocarbons, and solvents.

Methods: Workers were classified in 20 different job-titles depending upon the type of activity. Standardized mortality ratios (SMRs) were computed using male residents of the Province of Genoa as the referent population.

Results And Conclusions: For the whole cohort significantly increased SMRs were detected for all causes, all cancers, liver, larynx, lung, pleural and bladder cancers, respiratory tract diseases, and cirrhosis of the liver. The analysis by job-title showed increased SMRs not only for pleural cancer, but also for lung, laryngeal cancers and respiratory tract diseases in occupations entailing heavy asbestos exposure. Bladder and liver cancers and liver cirrhosis mortality also appeared to be related to occupational exposure.

Copyright 2001 Wiley-Liss, Inc.

In plain English

This historical cohort study followed 3984 male workers employed between 1960 and 1981 in ship repair, refitting and construction at the harbor of Genoa, Italy, through 1 January 1996. Workers were exposed to asbestos fibers (type not named), welding fumes, silica dust, polycyclic aromatic hydrocarbons and solvents, with no exposure measurements reported. Deaths were compared with those expected from rates among male residents of the Province of Genoa. Of 3959 workers traced, 2376 had died. Deaths from all causes were nearly 18% higher than expected (standardized mortality ratio or SMR 118, 95% confidence interval or CI 113 to 122). Excesses appeared for pleural cancer (60 deaths, SMR 524, 95% CI 400 to 674), lung cancer (298 deaths, SMR 177, 95% CI 157 to 198), laryngeal, bladder and liver cancer, respiratory diseases and liver cirrhosis. There were also 18 asbestosis deaths. Insulation workers had the highest pleural cancer SMR (1368). The authors concluded that heavy asbestos exposure resulted in increased deaths from pleural, lung and laryngeal cancer and respiratory diseases. They said mixed exposures prevented identifying specific causes of the other excesses.

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: Historical (retrospective) cohort mortality study using standardized mortality ratios (observed divided by expected deaths), with male residents of the Province of Genoa as the comparison population
• Who was studied: 3984 male shipyard workers (ship repair, refitting and construction, not longshoremen) employed at the harbor of Genoa, Italy, between 1 January 1960 and 1 January 1981, followed to 1 January 1996. Vital status was traced for 3959 (99.4%), of whom 2376 had died; 25 were lost to follow-up; 79,576 person-years in total
• Exposure: Mixed shipyard exposures: asbestos fibers (fiber type not specified), welding fumes, silica dusts, polycyclic aromatic hydrocarbons and solvents. Exposure was assessed by job title (20 job titles, grouped), with no measured doses. Insulation workers were described as exposed to very high amounts of asbestos
• Main results:
  • Whole cohort: deaths from all causes were nearly 18% above expected (2,376 observed vs 2,019.8 expected; SMR 118, 95% CI 113 to 122)
  • Whole cohort: 60 pleural cancer deaths (11.5 expected), 7.4% of all cancer deaths, SMR 524 (95% CI 400 to 674)
  • Whole cohort: 298 lung cancer deaths (168.7 expected), SMR 177 (95% CI 157 to 198). Lung cancer mortality increased with time since first exposure and with length of exposure
  • Whole cohort: increased SMRs for cancers of the liver (34 deaths, SMR 186, 95% CI 129 to 260), larynx (32 deaths, SMR 164, 95% CI 112 to 232) and bladder (44 deaths, SMR 153, 95% CI 111 to 205)
  • Whole cohort: respiratory diseases had 256 deaths (SMR 164, 95% CI 144 to 185). There were 18 asbestosis deaths against 0.39 expected (SMR 4658, 95% CI 2,760 to 7,362)
  • Whole cohort: liver cirrhosis had 104 deaths (SMR 149, 95% CI 121 to 180)
  • Insulation workers (82 workers, 1,650 person-years): SMRs of 852 for laryngeal cancer (3 deaths), 313 for lung cancer (10 deaths), 1368 for pleural cancer (3 deaths) and 546 for respiratory tract diseases (13 deaths). The respiratory deaths included 9 of the cohort's 18 asbestosis deaths
  • Laryngeal and bladder cancer mortality reached statistical significance only after 40 years since first exposure and in workers with at least 25 years of exposure
  • Whole cohort: no excess for oro-pharyngeal cancer (SMR 97) or esophageal cancer (SMR 77). Cardiovascular mortality was lower than expected (790 deaths, SMR 87, 95% CI 81 to 94), which the authors attributed to a healthy worker effect
• The authors' conclusion: The authors concluded that heavy asbestos exposure experienced by these Genoa shipyard workers resulted in significantly increased mortality from pleural cancer, lung cancer, laryngeal cancer and respiratory tract diseases. They suggested that complex chemical exposures may be responsible for the bladder and urinary tract cancer excesses in some jobs, and that alcohol intake and viral infections did not seem to explain the liver cancer and cirrhosis excesses. They also suggested that falling SMRs by period of hire reflect improved working conditions
• Limitations the authors state:
  • The mixed exposures in the shipyard prevented identifying which specific occupational factors were responsible for the bladder, liver cancer and cirrhosis excesses
  • There were too few liver cases within specific job titles for a clear analysis of possible risk factors
  • The authors could not fully separate the effects of length of exposure and latency, because most bladder and larynx cases had both the longest exposure and the longest latency

Topics

Medical terms in this study, explained in our Lexicon: standardized mortality ratio (SMR), Laryngeal Cancer, Asbestos Exposure, Occupational Exposure.

Related studies

• Mortality among shipyard workers in Genoa, Italy — R. Puntoni, M. Vercelli, et al. (1979)
• Mortality among workers exposed to asbestos at the shipyard of Genoa, Italy: a 55 years follow-up — D.F. Merlo, M. Bruzzone, et al. (2018)
• Mortality among dock-yard workers in Genoa, Italy — R. Puntoni, L. Russo, et al. (1977)
• A historical cohort mortality study of workers exposed to asbestos in a refitting shipyard — N. Kurumatani, Y. Natori, et al. (1999)
• An updated historical cohort mortality study of workers exposed to asbestos in a refitting shipyard, 1947-2007 — K. Tomioka, Y. Natori, et al. (2011)
• A mortality cohort study among workers in a graphite electrode production plant in Italy — D.F. Merlo, S. Garattini, et al. (2004)

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