Asbestos-related cancers among 28,300 military servicemen in the Royal Norwegian Navy.

The thesis covers the establishment and quality controls of two cohorts of civilian and military personnel serving in the Royal Norwegian Navy (RNoN) after January 1, 1950, and two studies among male members of the military cohort. For the civilian cohort, the criterion for inclusion was all civilians who have served at any time during 1950–2005 in the Navy, while the military cohort was limited to officers and enlisted personnel. All branches of the Navy were covered, hereunder the Fleet, the Coast Guard and the Coastal Artillery. By 1950, the Norwegian Fleet was either destroyed during the Second World War (WWII) or out-dated. The rebuilding of the Navy was yet to begin, and Norway had just become a member of the North Atlantic Treaty Organisation (NATO) at the Treaty foundation in 1949. With its border with the Soviet Union in the north Norway became of strategic importance, and the Cold War shaped the design of the Norwegian Defence. The present work started in 2002 with establishment of the cohorts. The registration work resulted in a military cohort of 29 056 persons (2.5% women) with an average of 6.2 years service in the Navy. The cohort of 8 378 civilians (39% women) had an average of 11 years in the Navy. Both cohorts were regarded as virtually complete. The first cohort study dealt with asbestos related cancers among Navy vessels crews. Asbestos has been commonly used in shipbuilding for heat and sound insulation, and for fireproofing. Until 1987, asbestos aboard the Navy vessels potentially caused exposure to 11 500 crew members. Engine room crews were considered to experience higher exposure intensity than other crews aboard. Asbestos is the only environmental factor known to cause malignant mesothelioma, and an elevated incidence of this disease served as an indicator of asbestos exposure. The incidence of other potentially asbestos related cancers (lung, laryngeal, pharyngeal, stomach and colorectal cancers) was evaluated according to duty station and mesothelioma incidence. Elevated incidence of mesothelioma was found among engine room crews only, and the time from first exposure to date of diagnosis ranged from 28 to 48 years (median 41). The mesothelioma incidence offered no consistent explanation to the variation in incidence of other potentially asbestos-related cancers. The second cohort study examined the cause-specific mortality and cancer incidence compared to the national rates. Internal comparisons between vessel crews and land-based personnel were performed. A military career implies adaptation to a rigid disciplinary system, handling of weaponry, and a life at remote locations causing separation from family members. In foreign navies, a higher than average alcohol consumption with a negative impact on occupational efficiency and adverse health outcome, has been reported. Special attention was thus given towards deaths from violent causes, alcohol related diseases (mental and behavioural disorders due to use of alcohol, liver cirrhosis) and incidence of alcohol-related cancers (mouth, pharynx, larynx, oesophagus and liver cancer). For the cohort as a whole, the overall mortality was 16% lower than in the general Norwegian male population. The physical and psychological screenings for military service and the demand for “keeping up” during service imply that the Navy personnel were highly selected and expected to be healthier than the general population. This phenomenon has been termed “healthy soldier effect”. Overall cancer incidence was 6% higher, mostly due to excess prostate cancer and malignant melanoma and non-melanoma skin cancers. Death from violent causes (accidents and suicide) was 36% lower than expected. Both overall mortality and cancer were higher among sailors than among land-based personnel. No increased risk of alcohol related cancers or mortality was found for the cohort as a whole, but a higher risk was found among those serving aboard the vessels than for land based personnel.