8 Coverage of PM 2.5 Precursors Atmospheric chemistry leading to PM 2.5 formation is complex Proposed approach for PM 2.5 implementation and new source review: PM 2.5 direct emissions (includes organic carbon, elemental carbon, and crustal material) and SO 2 must be addressed NO x must be addressed in all areas, unless the State and EPA provide a demonstration finding that NO x is not a significant contributor in a specific area.
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