Environmental impact of shipping engines can be higher on a port-specific basis. Ultra-low sulfur diesel (ULSD) is a standard for defining diesel fuel with substantially lowered sulfur contents. As of 2006, almost all of the petroleum-based diesel fuel available in Europe and North America is of a ULSD type. In 2016 the IMO has made new sulfur regulations which must be implemented by larger ships by 2020. Of total global air emissions, shipping accounts for 18 to 30 percent of the nitrogen oxide and 9 percent of the sulphur oxides. Sulfur in the air creates acid rain which damages crops and buildings. When inhaled,
Lower sulfur oxides Lower sulfur oxides The lower sulfur oxides are a group of inorganic compounds with the formula SO, where m < 2n. These species are often unstable and thus rarely encountered in everyday life. They are significant intermediates in the combustion of elemental sulfur. Some well characterized examples include sulfur monoxide (SO), its dimer SO, and a series of cyclic sulfur oxides, SOx (x = 1, 2), based on cyclic S rings. Interest in the lower sulfur oxides has increased because of the need to understand terrestrial atmospheric sulfur pollution and the finding that the extraterrestrial atmospheres of Io, one of