MEPC continued its work on developing regulations to reduce emissions of other toxic substances from burning fuel oil, particularly NOx and SOx. Together with CO2, these significantly contribute to air pollution from ships, and are covered by annex VI of MARPOL,35 amended in 2008 to introduce more stringent emission controls. During its sixty-eighth session, MEPC considered a number of amendments to existing guidance and other issues related to air pollution measures, and: