The visit by Royal Caribbean’s Harmony of the Seas to Southampton has raised again the issue of the pollution caused by cruise lines. Noxious emissions and air pollution near airports is a major problem but pollution around marine ports is also an issue. In London and Southampton air pollution caused by marine transport is a major issue and there is evidence that it damages residents’ health.  Harmony of the Seas has two four-storey high 16-cylinder Wärtsilä engines which would, at full power, each burn 1,377 US gallons of fuel an hour, or about 66,000 gallons a day. The Guardian has a dramatic graphic revealing the scale of the emissions and quoting Daniel Rieger…