# Appendix O:

Insignificance of

NH 3 

# and VOCs to

PM2.5 Attainment in North CarolinaInsignificance of NH3 and VOCs to PM2.5 Attainment in North Carolina The Hickory And Greensboro-Winston Salem-High Point, NC PM2.5 Appendix O North Carolina Attainment Demonstration August 21, 2009 i (This page intentionally left blank)Insignificance of NH3 and VOCs to PM2.5 Attainment in North Carolina The Hickory And Greensboro-Winston Salem-High Point, NC PM2.5 Appendix O North Carolina Attainment Demonstration August 21, 2009 1 

### 1 Significance of Precursors Contribut ing to Fine Particulate Formation

The United States Environmental Protection Agen cy (USEPA) revised the National Ambient Air Quality Standards (NAAQS) for particulate ma tter in 1997 establishing fine particulates (particulate matter with aerodynamic diameter ≤ 2.5 micrometers or PM2.5) as a benchmark. The revised NAAQS for particulate ma tter set a daily standard of 65 μg/m 3 and an annual standard of 15.0 μg/m 3 . The daily PM2.5 standard was more recently revised in 2006 by lowering it to 35 μg/m 3 based on a review of the air quali ty criteria and the NAAQS, but the annual PM2.5 standard was retained at 15.0 μg/m 3 . Both of these revisions to the NAAQS for particulate matter are published in 40 CFR 50.7 and 40 CFR 50, Appendix N.

Areas designated as “nonattainment” for fine pa rticulates by the USEPA must submit formal implementation plans detailing how attainment will be met as outlined in the Clean Air Act (CAA). These implementation plans must outline th e measures that will be taken to curtail the concentrations of various polluta nts that are assumed to have si gnificant contributions to fine particulate nonattainment, in cluding sulfur dioxide (SO 2 ), nitrogen oxides (NOx), and PM2.5.

The USEPA, in 72 FR 20586, requires states to “e valuate and consider co ntrol strategies for

sources of SO 2 , direct PM2.5, and NOx emissions in all nona ttainment areas.” However, the rule

does allow states to make technical demonstrations to reverse the inclusion of NOx as precursor of PM2.5, or deem the precursor insignificant, based on geographical regions, emissions, etc.

This then eliminates the need to examine NOx control measures for purposes of reducing PM2.5 concentrations. Although NOx is a relatively minor precursor of PM2.5 in North Carolina, the State of North Carolina is foregoing a techni cal demonstration of NOx insignificance and will follow the requirements in 72 FR 20586 to include NOx as a precursor for addressing attainment of the 1997 and 2006 revisions of the PM2.5 NAAQS.

The two remaining species that comprise PM2.5, ammonia (NH 3 ) and volatile organic carbons (VOCs) have been deemed as insignificant contributors to the total mass of PM2.5 by the USEPA. With regards to NH 3 , 72 FR 20586 states NH 3 “is presumed not to be a PM2.5 attainment plan precursor, meaning that the State is not required to address [NH 3 ] in its attainment plan or ev aluate sources of [NH 3 ] emissions for reduction measures.” Likewise, the

final rule for VOCs states that “States are not required to address VOC in PM2.5 implementation plans and evaluate control measures for such pollutants unless the State or EPA makes a

technical demonstration that em issions of VOCs from sources in the State significantly

contribute to PM2.5 concentrations in a given nonattainment area.”



### 2 NH 3 

### and VOC Insignificance

The State of North Carolina agrees with the USEPA’s presumptive exclusion of NH 3 and VOCs with regards to the PM2.5 implementation pl an. Therefore, emission controls for NH 3 and VOCs are not considered as a part of the North Carolina Division of Air Quality’s (NCDAQ’s) PM2.5 attainment demonstration plan.