Retrospective assessment of exposure to carcinogens in Norway’s offshore petroleum industry

• Main Author: Steinsvåg, Kjersti
• Format: Dissertation
• Language: English

Objectives: The main research objective of the four articles comprising this dissertation was to provide retrospective exposure information for a planned study on cancer in a cohort within Norway’s offshore petroleum industry. Methods: Background information on possible exposure was obtained through company visits, including interviewing key personnel (n = 83) and collecting monitoring reports (n = 118) and other relevant documents (n = 329). The collected material was used to identify relevant carcinogens. Twenty-seven job categories were defined based on a previous questionnaire administered to present and former offshore employees in 1998. Descriptions of products containing known and suspected carcinogens, exposure sources and processes were extracted from the collected documentation and the interviews of key personnel (Article II). Exposure data on oil mist and oil vapour covered 37 drilling facilities and were analysed by descriptive statistics and by constructing linear mixed-effects models (Article I). A group of three university and five industry experts individually assessed the likelihood (unlikely, possible or probable) of exposure for combinations of 17 carcinogens, 27 job categories and four time periods (1970–1979, 1980–1989, 1990–1999 and 2000–2005). Each rater was to assess 1836 combinations based on summary documents on carcinogenic agents, which included descriptions of sources of exposure and products, descriptions of work processes carried out within the different job categories and monitoring data. Interrater agreement was calculated using Cohen’s kappa index and single and average score intraclass correlation coefficients. Differences in interrater agreement between the different time periods, raters, carcinogen class and amount of information provided were then studied (Article III). In subsequent plenary discussions, the experts agreed on exposed combinations. Agreement between the individual and the panel assessments was calculated using Cohen’s kappa index. Using the panel assessment as reference, sensitivity and specificity were estimated (Article IV). Results: This study indicated possible exposure to the following known and suspected carcinogenic agents, mixtures or exposure circumstances: benzene; mineral oil – inhalation exposure; mineral oil – skin exposure; crystalline silica; asbestos; refractory ceramic fibres; formaldehyde; tetrachloroethylene; trichloroethylene; welding; nickel compounds; chromium [VI]; lead; crude oil