Cancer incidence among 41 000 offshore oil industry workers
Background Cancer incidence among Norwegian offshore oil industry workers has been studied in two equally sized cohorts of 28000 workers, in a survey-based cohort study followed 1999–2005 and a register-based cohort study followed 1981–2003.
Aims To determine the overall cancer incidence in both cohorts merged, with an extended follow-up.
Methods The merged cohort yielded 41140 individuals followed for cancer diagnoses 1999–2009. Standardized incidence ratios (SIRs) with 95% confidence intervals (CIs) were computed by gender and by period of first employment using cancer registry data.
Results Among female workers, the total number of cancers was slightly higher than expected (SIR 1.17, 95% CI 1.02–1.34), and excesses of acute myeloid leukaemia (AML) (SIR 5.29, 95% CI 1.72–12), malignant melanoma (SIR 2.13, 95% CI 1.41–3.08) and lung cancer (SIR 1.69, 95% CI 1.03–2.61) were observed. Among male workers, the total number of cancer cases was close to that expected (SIR 1.03, 95% CI 0.99–1.08), but cases of pleural cancer (SIR 2.56, 95% CI 1.58–3.91) and bladder cancer (SIR 1.25, 95% CI 1.05–1.49) were higher than expected. Among male workers first employed before 1986, the numbers of observed cancer cases were higher than expected for most sites, while this was not evident among those employed later.
Conclusions Further studies with exposure data and confounder control are needed to address whether the observed excesses of pleural cancer and AML can be attributed to offshore work.