Data collection and participants

For the qualitative part of the study, semi-structured in-depth interviews were conducted with seafarers of one of the vessels in the period of 6 months from May to October 2016. To achieve better understanding about working and living conditions at sea – which will improve the quality of qualitative analysis – the main researcher who was native Persian speaker stayed onboard during the mentioned period and all interviews were done on board. An interview guide was developed by research team members according to the primary research questions.

The participants were selected by maximum variation purposive sampling, [23] continued until data saturation. Saturation is reached when no new themes can be found in the interviews [24]. Participants were male seafarers > 18 years with different ranks and job categories on board of one of the multinational VLCC tankers. Having at least 6 months of sea service before joining this vessel and being fluent in Persian language were inclusion criteria. Maximum diversity of information was achieved by including staff members from the three following groups: 1) deck professionals: captain, duty officers, and sailors 2) engine workers: chief engineer, electrician, duty officers, and engine sailors 3) kitchen staff: chief cook, cooks, and waiters.

Before each interview, the purpose of the study was explained. Written informed consent for interviewing and audio recording were obtained from those willing to participate. Individual in-depth interviews were conducted in a private relaxed environment. Additional questions could be asked during the interview in response to the participant’s statements to achieve comprehensive answers to the research questions. The interviewer made field notes for the key points mentioned in the interview and on participants’ body language. Each interview lasted up to 1 h (ranging 35–60 min). All interviews were transcribed verbatim.