Mortality among workers exposed to asbestos at the shipyard of Genoa, Italy: a 55 years follow-up

Our plain-English summary of Mortality among workers exposed to asbestos at the shipyard of Genoa, Italy: a 55 years follow-up, by D.F. Merlo, M. Bruzzone, P. Bruzzi, et al (Environmental Health, 2018).

The study

• Authors: D.F. Merlo, M. Bruzzone, P. Bruzzi, E. Garrone, R. Puntoni, L. Maiorana, M. Ceppi
• Journal: Environmental Health
• Published: 2018;17(1):94
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Exposure to asbestos remains a global issue due to its massive use in the twentieth century and its long environmental persistence. Exposure to asbestos still occurs during dismantling of ships and vessels, buildings renovation, mining operations, and is reported in developing countries. Current estimate report exposure of hundreds of million people in occupational settings in countries where its use remains unregulated.

Methods: We conducted a historical prospective cohort mortality study aimed at estimating mortality from specific causes, the temporal changes of pleural and lung cancer mortality, and the attributable fraction (AF) of lung cancer deaths following asbestos exposure. The study included 3984 shipyard workers employed at the shipyard of Genoa, Italy, between 1960 and 1981 and followed up to December 2014. Standardized Mortality Ratios (SMR) and their 95% confidence intervals (95%CI) were computed.

Results: Overall deaths recorded were 3331 (83.6%). Excess mortality was observed for all cancers (SMR = 127, 95%CI:120-134), pleural mesothelioma (575, 469-697), cancers of the larynx (183, 134-244) and of the lung (154, 139-170), and for respiratory tract diseases (127, 114-141), including asbestosis (2277, 1525-3270). Ninety out of 399 deaths (22.6%) from lung cancer were attributed to asbestos exposure. The estimated lung cancer AF was 49.3% in workers with the highest SMR for pleural cancer. Median latency times for pleural and lung cancer were 42.8 years (minimum latency: 9.3 years) and 38.7 years (minimum latency: 6 years). The peak of mesothelioma incidence, expected in Italy in the period 2015-2024, was confirmed.

Conclusions: The long follow-up period of our study allowed the detection of a substantial disease burden following asbestos exposure. These findings support the urgent need for the prevention of asbestos related diseases through the implementation of asbestos ban worldwide, including those countries where asbestos is still mined, manufactured and used.

In plain English

This study followed 3,984 men employed at the Genoa, Italy, shipyard between January 1960 and January 1981 until the end of 2014. By then 3,331 (83.6%) had died. Their deaths were compared with those expected from Liguria Region male death rates. On this scale (the SMR), 100 means as many deaths as expected; ranges in brackets are 95% confidence intervals. Deaths from all causes were not raised (SMR 99, 96–103), but deaths from all cancers were (SMR 127, 120–134). There were 103 pleural cancer deaths (SMR 575, 469–697), 399 lung cancer deaths (SMR 154, 139–170), 46 laryngeal cancer deaths (SMR 183, 134–244) and 29 asbestosis deaths (SMR 2277, 1525–3270). Insulation workers had the highest pleural cancer SMR, 1703, but with a wide range (552–3974). Using each trade's pleural cancer SMR as a stand-in for asbestos exposure, the authors attributed about 90 of 399 lung cancer deaths (22.6%) to asbestos. Pleural cancer death rates rose throughout follow-up. The authors concluded this confirms the link between asbestos and pleural, lung and laryngeal cancer and respiratory diseases. They lacked asbestos measurements and individual smoking data.

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 prospective (retrospective) cohort mortality study comparing observed deaths with deaths expected from regional rates (standardized mortality ratios); an extension of an earlier follow-up of the same cohort by 19 years
• Who was studied: 3984 male workers ever employed at the shipyard of Genoa, Italy, between January 1960 and January 1981, followed from January 1, 1960 to January 1, 2015 (99,169 person-years). At the end of follow-up, 638 (16%) were alive, 3331 (83.6%) had died and 15 (0.4%) were lost to follow-up. The comparison was the male population of the Liguria Region.
• Exposure: Asbestos at the shipyard. Fiber types are not named. The authors describe asbestos used in Italian shipyards to insulate boilers, steam and hot water pipes and air conditioning systems, present in construction sheets and sprayed on surfaces. Workers were also exposed to solvents, welding fumes, polycyclic aromatic hydrocarbons and metal-working fluids. Exposure was not measured. The analysis used job trade, length of employment, age and period of hire, and time since first hire, and it used trade-specific pleural cancer SMRs as a stand-in for exposure level.
• Main results:
  • Whole cohort: deaths from all causes were not increased (SMR 99, 95% CI 96–103).
  • Whole cohort: there were 103 pleural cancer deaths against 17.9 expected (SMR 575, 95% CI 469–697).
  • Whole cohort: there were 399 lung cancer deaths against 259.5 expected (SMR 154, 95% CI 139–170).
  • Whole cohort: there were 46 laryngeal cancer deaths against 25.1 expected (SMR 183, 95% CI 134–244).
  • Whole cohort: deaths from respiratory diseases were increased (SMR 127, 95% CI 114–141). Of these 359 deaths, 29 (8.1%) were due to asbestosis (SMR 2277, 95% CI 1525–3270).
  • Whole cohort: four peritoneal neoplasm deaths were observed (SMR 181, 95% CI 49–463). This confidence interval includes 100.
  • Whole cohort: deaths from cardiovascular diseases were lower than expected (SMR 74, 95% CI 70–79).
  • Lung and pleural cancer mortality rose with length of employment at the shipyard (trend p = 0.031 for lung and 0.063 for pleural cancer).
  • Insulation workers had the highest trade-specific pleural cancer SMR point estimate (1703, 95% CI 552–3974). The interval is wide.
  • Insulation workers also had a lung cancer SMR of 397 (95% CI 239–623).
  • Trades with the highest pleural cancer SMRs had lung cancer SMRs 1.97 times those of the reference group of trades (RR 1.97, 95% CI 1.21–3.27). Within this group, the estimated fraction of lung cancer attributable to asbestos was 49.3%.
  • Across the cohort, an estimated 90 (22.6%) of the 399 lung cancer deaths were attributed to asbestos.
  • Pleural cancer death rates rose throughout follow-up, more steeply in 1990–2014.
  • Lung cancer death rates reached a plateau in 1990–1994 and stayed stable to the end of follow-up.
  • The median time from first hire to death was 38.7 years for lung cancer and 42.8 years for pleural cancer.
• The authors' conclusion: The authors concluded that the long follow-up revealed a substantial disease burden following asbestos exposure at the shipyard, confirming the link between asbestos exposure and pleural, lung and laryngeal cancer and respiratory diseases including asbestosis.
• Limitations the authors state:
  • There were no industrial hygiene data or measurements of asbestos fibers or other occupational agents.
  • There were no individual smoking data, so smoking could not be directly accounted for.
  • The attributable-fraction calculation assumed a similar proportion of smokers across trades, which could not be proven.
  • Using pleural cancer SMRs as a stand-in for exposure is a purely statistical approach that adds uncertainty to the estimated number of asbestos-attributed lung cancers.
  • The authors consider the attributable-fraction estimate likely to be an underestimate, because the reference trades themselves had raised pleural cancer mortality.
  • Length of employment, used as a stand-in for exposure, may not have fully captured exposure intensity.
  • The cohort was too small to address whether mesothelioma risk keeps increasing or declines after very long latency.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Shipyards and maritime work.

Medical terms in this study, explained in our Lexicon: Lung Cancer, Asbestos Exposure, standardized mortality ratio (SMR), confidence interval, Pleural Mesothelioma, Latency, Mesothelioma.

Related studies

• Mortality among shipyard workers in Genoa, Italy — R. Puntoni, M. Vercelli, et al. (1979)
• A historical cohort mortality study among shipyard workers in Genoa, Italy — R. Puntoni, F. Merlo, et al. (2001)
• Mortality among dock-yard workers in Genoa, Italy — R. Puntoni, L. Russo, et al. (1977)
• Lung and pleural CT signs predict deaths: 10-year follow-up after lung cancer screening of asbestos-exposed workers — T. Vehmas, P. Oksa, et al. (2012)
• Asbestos exposure and cancer mortality among petroleum refinery workers: a Poisson regression analysis of updated data — F. Montanaro, M. Ceppi, et al. (2004)
• Mortality among shipyard Coast Guard workers: a retrospective cohort study — S. Krstev, P. Stewart, et al. (2007)

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