FIGURE 1-2 National average emission categories for carbon monoxide (CO), sulfur dioxide (SO2), nitric oxide and nitrogen dioxide (NOx), volatile organic compounds (VOCs), particulate matter less than 10 micrometers in diameter (PM10), and particulate matter less than 2.5 micrometers in diameter (PM2.5) for 2001. For primary PM10 and PM2.5, a significant fraction of the PM fugitive dust emissions return to the ground after a few minutes. Biogenic emissions (such as VOC emissions from vegetation and NOx emissions from soil microbial processes) are not included. SOURCE: Adapted from EPA 2003a.



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