Cargo ships are significant sources of global air pollution because of their fuel oil. Most ships burn something called “bunker fuel” which is a pitch-black, molasses-thick fuel made from the dregs of the oil refining process. It is loaded with sulfur, so when it is burned it produces noxious gases and fine particles that can harm human health and the environment. Because bunker fuel is made from petroleum refining residues, waste byproducts sometimes end up in the mix, making the stuff even a worse source of pollution.
