As he is working for a big international construction company, you can probably gain some comfort in the knowledge that they will a provide a safe working environment (as far as possible). I would imagine 24 hour armed security protection, etc.
Large international companies have a reputation to maintain and typically they will do their utmost to protect their employees from any danger.
From my limited experience of working in less hospitable places (not any active war zones), the most dangerous part of the time spent is the travel between airport and worksite/accommodation.