¹Institut für Medizinische Biometrie, Epidemiologie und Informatik der Universitätsmedizin der Johannes Gutemberg-Universität, Mainz, Germany
²Istituto di Fisiologia Clinica del Consiglio Nazionale delle Ricerche, Lecce, Italy
³Asl Brindisi, Unit of Statistics and Epidemiology, Brindisi, Italy
⁴Asl Brindisi, Service of Prevention and Safety at Work, Brindisi, Italy
⁵Radiotherapy, Asst Papa Giovanni XXIII, Bergamo, Italy
⁶Cardiology, Department of Cardiac Thoracic Vascular Sciences and Public Health, University of Padova, Padova, Italy
⁷Universitätsmedizin Mainz, Mainz, Germany

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Introduction: The production of polyvinyl chloride (PVC) involves the use of numerous chemical substances. Some of these are probably or certainly carcinogenic [1] and capable of inducing tumours in the liver (angiosarcoma), the haematolymphopoietic system (leukaemia and lymphoma), the lungs, and the brain. PVC is a polymer of the monomer vinyl chloride, an odourless and colourless gas present in high concentrations in production plants during the polymerization and subsequent extrusion processes. In Italy, PVC was produced at several petrochemical plants. PVC production in Brindisi started in 1963 and ended in 1995 [2], [3].

At the end of the 1990s, several Courts in Italy – including the one in Brindisi – initiated criminal proceedings against plant managements due to working conditions considered to be hazardous to health. The aim of our study is to evaluate the mortality pattern among workers of the Brindisi cohort, which was enrolled during those proceedings [4].

Methods: Vital status and causes of death (ICD-10) were updated by the local health authority in Brindisi using health, administrative, and tax data-bases. The outcome of interest included overall mortality and mortality for specific causes. For internal comparison, we chose a parametric approach and used an additive failure time model. For cause of death specific models, other and potentially competing causes of death were treated as censored. The logarithm of the cumulative exposure to vinyl chloride for 1970-1996 was included in the model. For risk communication purpose the exposure was also used as binary-variable with respect to the median. All estimates were adjusted for age at recruitment.

Results: The cohort consisted of 1756 workers. Information on exposure to vinyl chloride was available for 1263 workers (50,434 person-years under risk). Causes of death were available for 78% of the 583 deceased workers. 14 persons were lost to follow up. The estimated median survival time among most exposed persons was 2.5 years less than among least exposed ones (95% confidence interval: -0.7;-4.3). The median survival time decreased by -0.6 years (-1.0;-0.2) for each unit increase in the logarithmic of the exposure. Strong association with exposure were found for lung-cancer and especially for liver-cancer.

Discussion: We found differences in the survival times among most exposed workers compared to least exposed for overall and cause-specific mortality. Some limitations must be considered when interpreting the study results. Causes of death were more often missing for elderly workers and for those with higher exposure. Thus, the high percentage of unknown death certificates may have biased the results for cause-specific mortality and associations are unlikely to be overestimated. Data on potential confounders like smoking and alcohol consumption were not available. However, it is unlikely that smoking habits and alcohol consumption were associated with exposure.

Conclusion: Results of our study confirm preceding findings of liver tumours risk and give some evidence of association between lung cancer and exposure to vinyl chloride. An analysis with external comparison is also up coming.

The authors declare that they have no competing interests.

The authors declare that an ethics committee vote is not required.

References

[1] International Agency for Research on Cancer. Chemical Agents and Related Occupations. Volume 100 F. A Review of Human Carcinogens. 2012.
[2] Bertazzi PA, Villa A, Foa V, Saia B, Fabbri L, Mapp C, Marcer C, M. M, Marchi M, Mariani F, et al. An Epidemiological Study of Vinyl Chloride Exposed Workers in Italy. Archives of Industrial Hygiene and Toxicology. 1979;30(suppl.):379-397.
[3] Simonato L, L'Abbe KA, Andersen A, Belli S, Comba P, Engholm G, Ferro G, Hagmar L, Langard S, Lundberg I, et al. A collaborative study of cancer incidence and mortality among vinyl chloride workers. Scand J Work Environ Health. 1991;17(3):159-169.
[4] Maltoni C. Consulenza Tecnica Medico-Legale del CTU Professor Cesare Maltoni, nel procedimento N. 332/96 RGNR relativo alla controversia promosssa dai Pubblici Ministeri Dottor Nicola Piacente e Dottor Emilio Arnesano nei confronti di EVC (Ex Enichem, Ex Montedison). Brindisi: Tribunale di Brindisi; 2000.