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Seafarers still run a greater risk of developing cancer than the rest of the population, even though the differences have radically decreased. Women employees at sea have lower risks of cancer than shore-based employees. The results come from a study at the University of Gothenburg.

Just over one third of all Swedes will suffer from some form of cancer during their lifetimes. For men working at sea, this risk is about 5% higher.

”It is mainly lung cancer and mesothelioma that are more common among seafarers, but also leukaemia,” says Karl Forsell, a medical doctor who carried out the study entitled Work environment and lifestyle factors that cause cancer among seafarers.

Lung cancer is mainly associated with lifestyle factors such as smoking, but work environment factors such as exposure to diesel fumes on the car deck and incomplete combustion of fuels in engines are both suspected of increasing the risk of cancer. There is a clear link between mesothelioma and exposure to asbestos, which primarily affects engine room staff. Despite the fact that asbestos has been banned on Swedish ships since 1988 and in international shipping since 2011, it is still found on board.

”Virtually all the engine-room employees I have talked to have been in contact with asbestos at some point during their working life,” says Karl Forsell. It often happened when they were doing work abroad with something that was unlabelled, but which later turned out to be asbestos.

Benzene linked to leukaemia

Previous research has shown that sea-farers working on tankers run a greater risk of developing leukaemia than the population as a whole. The current investigation confirms this. The cause is believed to be benzene, which has been known for a long time to result in different forms of leukaemia. The amount of benzene in petrol has decreased significantly from around 5% to 1%. Unfortunately it is found in larger quantities in a number of other refined oil and chemical products. 

”It is mainly on product tankers and chemical tankers that benzene occurs. If you switch between different products and clean the tanks between times, exposure levels become quite high, at least historically,” says Karl Forsell.

Even though seafarers suffer from leukaemia more often than Swedes in general, the risk has decreased. This positive development is at least partly due to the introduction of sealed systems for loading and unloading. In a general perspective, too, cancer risks among seafarers have fallen considerably. When Ralph Nilsson, a consultant doctor, published his study of cancer among seafarers in 1998, they ran a 30% greater risk of cancer than other occupations. Today the figure is down to 5%. 

”It is probably thanks to less smoking and stricter alcohol rules, as well as changes in the work environment,” says Karl Forsell.

Women healthier

Among women seafarers, the risk of developing cancer is actually less than in the same age groups ashore. Of a total of 75,745 seafarers who took part in the study, 36% were women. They had an almost 20% lower risk of developing cancer, excluding deck officers.

”The vast majority of women at sea work in the hotel and service sector, and it would have been interesting to compare them with a corresponding group ashore,” says Karl Forsell.

The most common forms of cancer among Swedes, prostate cancer and breast cancer, are less common among seafarers.

Karl Forsell is now continuing with a study of leukaemia among seafarers on tankers.

Linda Sundgren

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