The temporal development of regulations for the maximum allowed sulphur content of fuels. The regulations for shipping are set out in MARPOL Annex VI (IMO, 2008a) where SECA regulations apply only in Sulphur Emission Control Areas; the regulations for land transport refer to heavy vehicles in the European Union (EU, 1993, 1998, 2003). The decision to reduce the global marine fuel sulphur limit from 3.5% to 0.5% in 2020 rather than 2025 was taken very recently following a review of fuel availability (IMO, 2016). Note that the vertical scale is logarithmic. DOI: https://doi.org/10.1525/elementa.167.f2