Carbon monoxide
Other mobile sources and non-industrial combustion plants contribute significantly to the total emission of CO. Transport is the second largest contributor to the total CO emission. In 1990 a law forbidding the burning of agricultural crop residues on fields was implemented this caused significant reduction in CO emission. The emission decreased further by 45 % from 1990 to 2009, largely because of decreasing emissions from road transportation.
(Click the chart to view the background data)