Chemical exposure, night shift work and cancer risk among Norwegian offshore workers
In recent years, there has been increased awareness of benzene exposure, and the associated risk of cancer. Benzene is a volatile and colourless liquid found naturally in crude oil, gas and condensate (produced water).
Research suggests that benzene has a carcinogenic effect at lower concentrations than first thought. Studies also suggest that night shift work may increase cancer risk. The Cancer Registry of Norway has conducted studies looking at the association between benzene exposure and cancer of the skin, breast, lung, bladder, kidneys, lymphomas and leukemia. These studies were conducted on offshore workers who were employed between 1965 and 1998 using the Cancer Registry of Norway's Offshore cohort from 1998. However, there is a lack of studies on offshore workers with a work history after 1998, and studies on hydrocarbon exposure related to prostate cancer and colorectal cancer have not yet been conducted in this occupational group.
To obtain data on work history after 1998, the Cancer Registry of Norway is now establishing a cohort of offshore workers who work or have worked offshore since the 2000s until today. This cohort is based on helicopter transport back and forth to heliports, thereafter, called the Heliport cohort. You can read more about the data collection of the Heliport cohort here. The offshore cohort will be linked to the new Heliport cohort, and then linked to the Cancer Registry of Norway to study cancer risk.
To be able to look at the association between benzene exposure and cancer, updated exposure estimates for benzene exposure in the offshore working environment are being used. The exposure estimates have been calculated and prepared by occupational hygienists at the University of Bergen, who have benzene exposure as their area of expertise. The Heliport cohort contains information on shift work obtained through surveys and from the oil companies' registers. This will be used to look at the association shift work and cancer.
The present project aims to perform two cancer risk studies of prostate cancer and colorectal cancer (CRC), respectively, taking into account time-dependent chemical exposures, inclusive of benzene, and shift work schedules, with adjustment of known risk factors associated with lifestyle. More specifically, we want to study:
- Is there a dose-response relationship between increasing night shift work and prostate cancer and CRC risk in offshore petroleum workers?
- Is there a dose-response relationship between increasing hydrocarbon exposure and CRC or prostate cancer risk in offshore petroleum workers?
- Does shift-work influence the associations between benzene exposure and CRC risk in offshore petroleum workers?
The project has an active reference group consisting of representatives from employees, employers, and supervisory authorities. As of November 2022, the reference group consists of representatives from the Norwegian Confederation of Trade Unions, SAFE, the Federation of Norwegian Industries, the Petroleum Safety Authority Norway, the Norwegian Shipowners' Association and Equinor.