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,
Higher sulfur oxides Higher sulfur oxides Higher sulfur oxides are a group of chemical compounds with the formula SO where x lies between 0 and 1. They contain peroxo (O−O) groups and the oxidation state of sulfur is +6 as in SO. Monomeric SO can be isolated at low temperatures (below 78 K) following the reaction of SO and atomic oxygen or photolysis of SO–ozone mixtures. The favoured structure is: Colourless polymeric condensates are formed in the reaction of gaseous SO or SO with O in a silent electric discharge. The structure of the polymers is based on β-SO (one of the three