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,
Nitrogen dioxide NO exposure concentrations near roadways are of particular concern for susceptible individuals, including asthmatics, children, and the elderly. For limits in other countries see the table in the "Ambient air quality criteria" article. Nitrogen dioxide Nitrogen dioxide is the chemical compound with the formula . It is one of several nitrogen oxides. is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year which is used primary in production of fertilizers. At higher temperatures it is a reddish-brown gas that has a characteristic sharp, biting odor and is a prominent air pollutant.