Changes (%) in emissions of ozone precursors by source category, 1990-2007, EEA-32 (weighted by tropospheric ozone forming potential)

The graph above shows the emissions of ozone precursors (methane CH4; carbon monoxide CO; non-methane volatile organic compounds NMVOCs; and nitrogen oxides NOx) each weighted by a factor prior to aggregation to represent their respective tropospheric ozone formation potential (TOFP). The TOFP factors are: NOx 1.22, NMVOC 1, CO 0.11 and CH4 0.014 (de Leeuw 2002). Results are expressed in NMVOC equivalents (kilotonnes - kt). Data not available for Iceland (emissions of CO, NMVOC, NOx were not reported) and Malta (CO). 'Energy combustion' includes all energy-related emissions minus fugitive.