Power plants burning fossil fuels (coal, oil, and, to a lesser extent, natural gas) are the largest source of sulfur dioxide emissions globally. Coal, in particular, contains high levels of sulfur, and when burned, it releases large amounts of SO₂.   

• Locomotives, especially older ones, use diesel fuel which contains sulfur. While locomotives do contribute to sulfur dioxide (SO₂) emissions, their contribution is relatively minor compared to larger industrial sources.  

• Ships, particularly large cargo vessels and tankers, often use bunker fuel, a heavy, sulfur-rich fuel oil. This contributes significantly to SO₂ emissions, particularly in maritime regions.  However, they are still overshadowed by emissions from power plants 

• The process of extraction of metals from ore involves heating ores that contain sulfur compounds, releasing SO₂ into the atmosphere. However, its contribution is less than that of power plants.