Cohort study of workers employed in an Italian tire manufacturing plant, 1962–2004
To investigate mortality and bladder cancer incidence among workers of a tire manufacturing plant where antioxidants severely contaminated by beta-naphthylamine were never used.
Mortality follow-up was performed of 9,501 workers first hired between 1962 when the plant started operations and 2000. Person-years of observation from 1962 to 2004, expected deaths, and standardized mortality ratios (SMR) were calculated. Follow-up for bladder cancer incidence from 1988 to 2003 was carried out, and standardized incidence ratios (SIR) were calculated. Multivariable (Poisson) analyses of bladder cancer incidence and mortality by duration of employment (DOE) and time since first employment (TSFE) were performed.
Among men, SMRs were significantly reduced for all causes, all cancers, lung cancer, cardiovascular, and ischemic heart diseases. Bladder cancer mortality and leukemia mortality were close to expectation but increased with TSFE. Seventy-two incident cases of bladder cancer were observed (SIR = 1.15; 95 % confidence interval 0.90–1.44), and multivariable analysis suggested a possible increase in rate ratios with DOE. Among women, mortality was close to expectation, but the limited number of observed deaths prevented detailed analyses.
No significant cancer excess was observed. A suggestion of increased risks of bladder cancer and leukemias after extended TSFE was present in men, deserving consideration as exposure to carcinogens possibly occurred early in plant operation. Furthermore, this cohort of workers is still relatively young and less than 10 % have died. There was, thus, limited power to detect small increases in risk at rare cancer sites. Further epidemiological surveillance of this cohort is planned.
KeywordsRubber industry Cohort study Bladder cancer Leukemia
The authors would like to thank Ms. Antonella Stura and Ms. Manuela Gangemi for conducting the follow-up; Dr. Marco Gilardetti for performing record-linkage procedures; and Ms. Silvia Aimar, Ms. Gabriella Pera, and Dr. Marcella Occelli for collecting data on bladder cancer diagnoses in the hospitals of Cuneo province. We are also indebted to Dr. Dario Consonni for his precious advice in the statistical analyses and to Ms. Assunta Rasulo for her help with the statistical analyses. Plinio Amendola was partially supported by the Master in Epidemiology, University of Turin and Compagnia di San Paolo. Dario Mirabelli and Anna Maria Cacciatore received grants from Regione Piemonte, Ricerca Sanitaria Finalizzata. The funding bodies had no role in the study design; in the collection, analysis, and interpretation of data; in the writing of the report; and in the decision to submit the paper for publication.
Conflict of interest
The authors declare that they have no conflict of interest.
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