Objectives Increased cancer risks have been reported among workers in the rubber manufacturing industry employed before the 1960s, but it is unclear for workers hired subsequently. The present study focused on cancer incidence among rubber workers first employed after 1975 in Sweden and the UK.
Methods Two cohorts of rubber workers employed for at least 1 year were analysed. Standardised incidence ratios (SIRs), based on country-specific and period-specific incidence rates, were analysed for all cancers combined (except non-melanoma skin), bladder, lung, stomach cancer, leukaemia, non-Hodgkin's lymphoma and multiple myeloma. Exploratory analyses were conducted for other cancers with a minimum of 10 cases in both genders combined.
Results 16 026 individuals (12 441 men; 3585 women) contributed to 397 975 person-years of observation, with 846 cancers observed overall (437 in the UK, 409 in Sweden). No statistically significant increased risk was observed for any site of cancer. A reduced risk was evident for all cancers combined (SIR=0.83, 95% CI (0.74 to 0.92)), lung cancer (SIR=0.74, 95% CI (0.59 to 0.93)), non-Hodgkin's lymphoma (SIR=0.67, 95% CI (0.45 to 1.00)) and prostate cancer (SIR=0.77, 95% CI (0.64 to 0.92)). For stomach cancer and multiple myeloma, SIRs were 0.93 (95% CI (0.61 to 1.43)) and 0.92 (95% CI 0.44 to 1.91), respectively. No increased risk of bladder cancer was observed (SIR=0.88, 95% CI (0.61 to 1.28)).
Conclusions No significantly increased risk of cancer incidence was observed in the combined cohort of rubber workers first employed since 1975. Continued surveillance of the present cohorts is required to confirm absence of long-term risk and confirmatory findings from other cohorts would be important.
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Contributors The study Working Group comprised iPRI staff (MB, AK and PB) and national Principal Investigators, TS (UK) and KJ (Sweden). MB, PB and TS were involved in the planning of the study. TS supervised data gathering for the UK cohort. KJ supervised data gathering for Swedish cohort. MB and AK conducted data analysis. MB prepared the first draft of the manuscript. All authors contributed during the revision phase of the manuscript. All authors approved the final version submitted.
Funding The study was partially funded by an unrestricted research grant from the European Tyre and Rubber Manufacturers' Association (ETRMA) and was conducted and reported in full independence from the sponsor.
Competing interests None declared.
Ethics approval Not required for secondary use of data. IRB approval from both countries (United Kingdom and Sweden) covered already the use of these anonymised, non-identifiable cohort data.
Provenance and peer review Not commissioned; externally peer reviewed.
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