Fos-sur-Mer is a commune in the Bouches-du-Rhône department in southern France.GeographyFos-sur-Mer is situated about 50km north west of Marseille, on the Mediterranean coast, and to the west of the Étang de Berre. The city has 6km of sand beach.EconomyFos is the site of a major port development operated by the Autonomous Port of Marseilles. The facilities include container handling terminals and a gas (methane) terminal. The waterside location of the industrial zone is attractive to heavy industry including steel. The steel group ArcelorMittal has its Sollac Méditerranée plant here. The presence of the steel, chemistry and oil industries means that pollution levels are high.