Due to copyright issues, an electronic copy of the thesis must be ordered from the faculty. For the faculty to have time to process the order, the order must be received by the faculty at the latest 2 days before the public defence. Orders received later than 2 days before the defence will not be processed. After the public defence, please address any inquiries regarding the thesis to the candidate.
Trial Lecture – time and place
See Trial Lecture.
Adjudication committee
- First opponent: Senior professor Bengt Järvholm, Umeå University,
- Second opponent: Scientist Ann Olsson, WHO - International Agency for Research on Cancer,
- Third member and chair of the evaluation committee: Associate professor Randi Opheim, University of Oslo
Chair of the Defence
Professor Jahn Frederik Frøen, University of Oslo
Principal Supervisor
Senior Researcher Jo Steinson Stenehjem, Norwegian Institute of Public Health
Summary
This thesis is situated within occupational cancer epidemiology and examines occupational exposures and cancer incidence among Norwegian offshore petroleum workers.
It aimed to profile the Norwegian Offshore Petroleum Workers (NOPW) cohort and evaluate cancer incidence compared to the general population, harmonize work histories for exposure quantification, and examine associations between benzene exposure and risk of lung and colorectal cancer (CRC).
The NOPW cohort comprises approximately 28,000 offshore petroleum workers who completed a survey containing information on work history, sociodemographic characteristics, and lifestyle factors. Cancer incidence was assessed through linkage with the Cancer Registry of Norway. To improve exposure assessment, a harmonization method was developed to address overlapping employment records before linkage to job exposure matrices. Associations between occupational benzene exposure and cancer risk were examined prospectively among male cohort members.
The findings showed a small excess of overall cancer risk compared with the Norwegian general population, with increases of 7% among males and 13% among females. Elevated risks were observed for pleural mesothelioma, breast cancer, and prostate cancer in males, and for melanoma and acute myeloid leukaemia in females.
Harmonization of overlapping employment records reduced the cohort's total employment duration by 10%, demonstrating the importance of this procedure for accurate exposure assessment.
For lung cancer, a pattern of increased risk was observed with increasing benzene exposure, although these associations were not statistically significant for lung cancer overall. Positive associations were identified between duration of benzene exposure and lung adenocarcinoma.
For CRC, positive associations were found for overall CRC, right sided colon cancer, and rectal cancer with respect to both average exposure intensity and duration. No clear associations were found for left sided colon cancer, although an increased risk was observed in the highest quartile of average intensity compared with unexposed workers.
Overall, the thesis provides a detailed profile of the NOPW cohort, presents a method for handling overlapping employment records, and contributes with new insights into benzene’s etiological role for lung cancer and CRC.
Additional information
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