NO2 Average Values

Nitrogen Dioxide (NO2) is one of the six criteria air pollutants regulated by the United States Environmental Protection Agency (USEPA).  In order to characterize ambient air concentrations of NO2 in North Carolina, NO2 monitoring is conducted at six sites in four counties. Five of the six sites are located near urban centers in order to capture the highest expected NO2 concentrations. The sixth site, in Northampton County, is a special purpose monitor established in 2019 as a background monitoring site. 

 

To determine the 1-hour primary standard design value for NO2, USEPA uses a 3-year average of the annual 98th percentile of the daily 1-hour maximum concentration. For an area to be designated as an attainment area, that value must not exceed 100 parts per billion (ppb). In addition, USEPA has set an annual primary standard which requires that the average concentration of all 1-hour concentration values for a given calendar year not exceed 53 ppb.  All areas in North Carolina meet both the 1-hour and annual standards and are in attainment for NO2

   

 

Design Values for NO2

2017 - 2019

2017 - 2019

NC Map of NO2 Design Values (2017-2019) by CountyPlease click here to open the NO2 Design Values Map as a PDF.

 

The table below shows design values for each of the primary standards for NO2. The first column lists the county. The second and third columns describe the 1-hour primary standard design value: the second column lists the 3-year average of annual 98th percentile 1-hour daily maximum values for the site indicated in the third column. In counties with more than one NO2 monitoring site, the design value reported is the highest among the inclusive sites.

The fourth and fifth columns describe the annual primary standard design value. The fourth column is the 2019 arithmetic mean of all valid hourly concentrations for the site indicated in the fifth column. In counties with more than one NO2 monitoring site, the value reported is the highest average among the inclusive sites.

An asterisk (*) has been added to indicate those sites which have not operated for the entire 1- or 3-year period, but whose data have been included in this summary.

  1-hour Primary Standard Annual Primary Standard

County

Average 98th Percentile
(2017 - 2019)

Site Name

Annual Mean
(2019)

Site Name

Forsyth

36 ppb 

Hattie Avenue[1], [4]             

7 ppb

Hattie Avenue [1], [4]          

Mecklenburg 

37 ppb

Garinger [1], [3], [4]

11 ppb

Remount Road [1], [4]

Northampton* 13 ppb Northampton*[2] 2 ppb Northampton*[2]

Wake

35 ppb

Millbrook[1], [3]

9 ppb

Triple Oak [1]

[*] Indicates the site does not satisfy the summary criteria

Purpose of Monitor

[1] SLAMS – (State and Local Monitoring Stations) Network of monitoring stations that monitor ambient air concentrations for pollutants for which standards have been established. The scale of these sites can be either Neighborhood/Area Wide or Micro-scale/Near Road (Remount Road and Triple Oak). Hattie Avenue is a Neighborhood Scale Regional Administrator Required Monitoring Site.

[2] SPM – (Special Purpose Monitors) SPMs allow the capability of providing monitoring for various reasons such as special studies, modeling verification or compliance status, and other objectives. These monitors are not committed to any one location or for any specified period.

[3] NCORE – (National Core) Community-oriented multi-pollutant monitoring station used to evaluate the regional air quality models used in developing emission strategies and to track trends in air pollution abatement control measures’ impact on improving air quality.

[4] Local Program- Denotes a monitor that is operated by a local program.

2016 - 2018

2016 - 2018

   

Please click here to open the NO2 Design Values Map as a PDF.

For NO2, the United States Environmental Protection Agency (USEPA) uses a 3-year average of the 98th percentile of the daily maximum concentration to determine the design value for this pollutant.  The table below shows 3-year averages for the 98th percentile of daily maximum NO2 concentrations. The first column lists the county, the second lists the 3-year average 98th percentile value, the third column lists the site with the highest 3-year average.  The fourth column lists the arithmetic mean value of all hourly averages for that county. The fifth column lists the site with the highest mean value.  In Counties with more than one NO2 monitoring site, the value reported is the highest average among the inclusive sites.  An asterisk (*) has been added to indicate those sites which have not operated for the entire 3-year period, but whose data has been included in this summary.

County

Average 98th Percentile

Site Name

Arithmetic Mean

Site Name

Forsyth [4]

36 ppb 

Hattie Avenue[1]             

7 ppb

Hattie Avenue [1]           

Lee *

7 ppb 

Blackstone [2]

1 ppb

Blackstone [2]

Mecklenburg[4] 

38 ppb

Garinger [1], [3]

11 ppb

Remount Road [1]

Wake

36 ppb

Millbrook[1][3]

9 ppb

Triple Oak [1]

[*] Indicates the site does not satisfy the summary criteria

Purpose of Monitor

[1] SLAMS – (State and Local Monitoring Stations) Network of monitoring stations that monitor ambient air concentrations for pollutants for which standards have been established. The scale of these sites can be either Neighborhood/Area Wide or Micro-scale/Near Road (Remount Road and Triple Oak). Hattie Avenue is a Neighborhood Scale Regional Administrator Required Monitoring Site.

[2] SPM – (Special Purpose Monitors) SPMs allow the capability of providing monitoring for various reasons such as special studies, modeling verification or compliance status, and other objectives. These monitors are not committed to any one location or for any specified period.

[3] NCORE – (National Core) Community-oriented multi-pollutant monitoring station used to evaluate the regional air quality models used in developing emission strategies and to track trends in air pollution abatement control measures’ impact on improving air quality.

[4] Local Program- Denotes a monitor that is operated by a local program and by NCDAQ.

2015 - 2017

2015 - 2017

 

 

 Please click here to open the NO2 Design Values Map as a PDF.

County

Average 98th Percentile

Site Name

Arithmetic Mean

Site Name

Forsyth

36 ppb [a]

Hattie Avenue [1]

7 ppb

Hattie Avenue [1]

Lee

8 ppb [a]

Blackstone [2]

1 ppb

Blackstone [2]

Mecklenburg 

39 ppb

Remount Road [1]

11 ppb

Remount Road [1][*]

Wake

36 ppb

Millbrook [1]

9 ppb

Triple Oak [1]

2012-2014

2012-2014

 

Table 1. The following table shows 3-year averages for the 98th percentile of daily maximum NO2 concentrations. The first column lists the county, the second lists the average value for that county.

County Average 98th Percentile
Forsyth 41 ppb
Mecklenburg 41 ppb
Previous Years