Mortality for Mesothelioma and Lung Cancer in a Cohort of Asbestos Cement Workers in BARI (Italy): Time Related Aspects of Exposure

Our plain-English summary of Mortality for Mesothelioma and Lung Cancer in a Cohort of Asbestos Cement Workers in BARI (Italy): Time Related Aspects of Exposure, by F. Cuccaro, A.M. Nannavecchia, S. Silvestri, et al (Journal of Occupational and Environmental Medicine, 2019).

The study

• Authors: F. Cuccaro, A.M. Nannavecchia, S. Silvestri, A. Angelini, V. Coviello, L. Bisceglia, C. Magnani
• Journal: Journal of Occupational and Environmental Medicine
• Published: 2019;61(5):410-416
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objective: In this cohort mortality study we used an exposure index to evaluate individual cumulative exposure as proxy of asbestos dose and we evaluated change in cancer mortality pattern after long time since the end of exposure.

Methods: We calculated standardized mortality ratios (SMRs) for several causes of death stratified by latency, cumulative exposure, and time since last exposure (TSLE).

Results: Latency: we observed a peak and then a decrease in SMR for lung, pleural, and peritoneal cancer. Cumulative Exposure: We observed a peak and then a decrease in SMR for lung and pleural cancer, not for peritoneal cancer. TSLE: Pleural cancer SMR peaked at 20 to 29 years, then decreased, peritoneal cancer SMR reached a plateau after 20 years and lung cancer mortality was in excess in each class.

Conclusions: We found different patterns in mortality in the main asbestos-related tumors.

In plain English

This mortality study followed 414 men who worked at the Fibronit asbestos cement plant in Bari, Italy. They were employed there in 1972 or hired later, and deaths were tracked to 2015. The plant's asbestos was mostly chrysotile, with crocidolite and small amounts of amosite. The authors estimated each worker's cumulative exposure and compared deaths with the number expected from regional Apulian rates. There were 257 deaths. Lung cancer deaths were about twice the expected number (43 observed, 21.9 expected). Pleural cancer (19 deaths), peritoneal cancer (8 deaths) and pneumoconiosis (38 deaths) were many times more frequent than expected. No pleural or peritoneal cancer deaths occurred in the first 10 years after workers left the plant. Pleural cancer mortality was highest 20 to 29 years after exposure ended and lower after 30 years, a figure based on one death. Peritoneal cancer mortality kept rising, and lung cancer stayed around twice the expected level. Death counts in these groups were small. The authors concluded that the cohort had a large excess of these diseases and that the time patterns differed by tumor type. They noted that they had no direct smoking data and missed workers who left before 1972.

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 comparing observed deaths with expected deaths (standardized mortality ratios, SMRs, where 100 means as expected), stratified by latency, duration of exposure, cumulative exposure and time since last exposure
• Who was studied: 414 male workers of the Fibronit (previously SAPIC) asbestos cement plant in Bari, Italy: 325 present in early 1972 and 89 hired later (377 blue-collar, 29 white-collar, 8 who moved from blue-collar to white-collar jobs). They were hired between 1934 and 1982 and followed from 1972 to 2015, for 13,027 person-years.
• Exposure: Asbestos cement manufacturing (flat and corrugated slabs, pipes, chimneys, special parts) using an asbestos mixture of 70% to 80% chrysotile, 15% to 20% crocidolite and small percentages of amosite. Exposure was estimated as an individual cumulative exposure index, with a mean of 55.6 fibers/cm3-years (range 0.1 to 157). The assigned blue-collar level for 1934 to 1974 was 3.88 fibers/cm3.
• Main results:
  • Whole cohort: 257 deaths. All causes SMR 123 (95% CI 109 to 139). All malignant tumors SMR 167 (137 to 201). Lung cancer SMR 196 (142 to 264). Pleural cancer SMR 3616 (2177 to 5646). Peritoneal cancer SMR 3164 (1366 to 6234). Pneumoconiosis SMR 11470 (8117 to 15743). Circulatory diseases were lower than expected, SMR 54 (39 to 74).
  • Observed versus expected deaths: lung cancer 43 versus 21.9, pleural cancer 19 versus 0.5, peritoneal cancer 8 versus 0.3, pneumoconiosis 38 versus 0.3.
  • By time since first exposure (latency): lung cancer SMR peaked at 30 to 39 years and decreased slightly afterward. The first pleural cancer deaths occurred at 30 to 39 years, with a reduction in the last latency class. Peritoneal cancer deaths first appeared at 40 to 49 years, with a slight decrease at 50 or more years.
  • By thirds (tertiles) of cumulative exposure: lung cancer SMR rose from 174 to 187 to 207. Pleural cancer SMR peaked in the middle tertile (5514). There were no peritoneal cancer deaths in the lowest tertile.
  • By time since last exposure: no pleural or peritoneal cancer deaths occurred in the first 10 years after exposure ended. Pleural cancer SMR peaked at 20 to 29 years (SMR 5828, 11 deaths) and was lower at 30 or more years (SMR 1277, 1 death). Peritoneal cancer SMR rose from 3680 (10 to 19 years, 3 deaths) to 5333 (20 to 29 years, 4 deaths) to 8154 (30 or more years, 1 death).
  • Lung cancer SMR was around 200 in every class of time since last exposure: 204 at 0 to 9 years, 194 at 10 to 19, 206 at 20 to 29, and 240 at 30 or more. The confidence intervals for the 0 to 9 years class (93 to 387) and the 30 or more years class (88 to 521) extend below 100.
  • Pneumoconiosis deaths (34 of 38 attributed to asbestosis) occurred only in workers with cumulative exposures greater than 37 fibers/cm3-years.
• The authors' conclusion: The authors concluded that the study confirms a large excess mortality for pleural cancer, peritoneal cancer, lung cancer and asbestosis in the Fibronit cohort. They also concluded that the patterns over time differed among these cancers and were rather consistent with the scientific literature. They suggested that the drop in pleural cancer long after exposure ended may relate to clearance of fibers, which may be less efficient in the peritoneum.
• Limitations the authors state:
  • Left truncation: the cohort included only workers present in 1972 or hired later, so workers who left the plant before 1972 were lost. The authors considered it likely that the SMRs were underestimated as a result.
  • No direct information on workers' smoking habits was available.
  • Workers could not be individually assigned to specific tasks, so a plant-level index assuming 50% active and 50% passive exposure was used.
  • The joint analysis of cumulative exposure and time since last exposure was not interpretable for pleural and peritoneal cancers because of very small numbers. The peritoneal cancer pattern could reflect random fluctuation in a small cohort.
  • Deaths were counted as pneumoconiosis rather than asbestosis, and peritoneal cancer included retroperitoneal cancer. The authors said this could at most have led to underestimated SMRs for these causes.

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma, Lung Cancer, Asbestos-Cement, Cumulative Exposure, standardized mortality ratio (SMR), Latency.

Related studies

• Cumulative asbestos exposure and mortality from asbestos related diseases in a pooled analysis of 21 asbestos cement cohorts in Italy — F. Luberto, D. Ferrante, et al. (2019)
• Mortality in asbestos cement workers in Pavia, Italy: A cohort study — E. Oddone, D. Ferrante, et al. (2017)
• A cohort study on mortality among wives of workers in the asbestos cement industry in Casale Monferrato, Italy — C. Magnani, B. Terracini, et al. (1993)
• Mortality in a cohort of cement workers in a plant of Central Italy — F. Giordano, V. Dell'orco, et al. (2012)
• The relationship between malignant mesothelioma and an asbestos cement plant environmental risk: a spatial case-control study in the city of Bari (Italy) — M. Musti, A. Pollice, et al. (2009)
• 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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