Deckhands on tankers carrying carcinogenic benzene in the cargo are exposed to high benzene levels in certain situations. Seamen who have worked on older tankers may have a greater risk of blood cancers. This has been demonstrated in a thesis at the University of Gothenburg.
Karl Forsell is a senior consultant at Occupational and Environmental Medicine at Norrland’s University Hospital, and he has studied exposure to benzene among Swedish seamen and whether the substance is absorbed in the body. He has also examined the frequency of blood cancers among seafarers, which are associated with exposure to benzene. The results show that seamen on tankers carrying benzene are subjected to particularly high benzene levels when loading, unloading and cleaning tanks. Biomarkers also show that benzene is absorbed in the body either through the inhalation of vapours or via direct contact with the skin during work, and a suspected risk of blood cancers was also found. Between 1985 and 2014 there were 315 cases of blood cancers among Swedish seamen. Most at risk were those who had started working on tankers before 1985. Karl Forsell does not think there is any cause for concern among those who have worked on older tankers, though.
Only isolated cases
”Even if the risk appears to be increasing, it is an unusual form of cancer and there are only very few cases per year,” he says.
The risk of blood cancers was less among those who have worked on tankers in more recent years. This could be due to several contributing factors, according to Karl Forsell. One probable reason is that the concentration of benzene in petrol has fallen sharply due to regulations at the EU level. In 1998 the maximum permitted benzene content of petrol products was reduced from 5% to 1%, and benzene levels are often less than 1% nowadays. Another possible reason for the declining risk of cancer may be changes in ship design. Modern tankers are often equipped with a closed system, which means that contact with the cargo is significantly decreased.
“But there are still some jobs with a relatively high exposure to benzene, such as cleaning the tanks. These results may also be interesting from an international perspective, where older ships are still in use,” says Karl Forsell.
In addition to the cancer studies, the thesis also includes a wide review of seafarers’ work environment. It is based on a survey of nearly 2,000 Swedish seafarers in different jobs on various types of ships. The questionnaire results indicate several problem areas, such as strain injuries, fatigue, stress, noise and whole-body vibration. Symptoms of physical strain problems were mainly reported by engine room and service staff. Noise was a common problem on board, especially in the engine rooms. Almost half the personnel there (46%) reported some loss of hearing.
“Noise levels in shared spaces on board were monitored in Norway and Denmark, and in some cases they exceeded the risk levels. This is an area I would like to examine in more detail on Swedish ships,” says Karl Forsell.
Majority felt good
Questions on the psycho-social work environment were also included in the questionnaire, and the results show major problems here. Among the men that responded, 22% stated that they had been harassed at work at some time during the last year. The proportion of women reporting harassment was 45%. At the same time the overall majority of respondents, 77%, said that they felt good or very good in general. 85% answered that they had good or very good working capacity.
The thesis is called, “Health hazards and cancer in relation to occupational exposures among Swedish seafarers”. It was presented at the University of Gothenburg on 11 December last year.
Linda Sundgren, text and photo