1.09
                                                                           0.19
                                                                           20.5
                                                                           1.58
                                                                           70.9
                                                                           0.34

Summer
                                                                            237
                                                                           1.18
                                                                           0.92
                                                                          -0.26
                                                                          -21.8
                                                                           0.58
                                                                           38.2
                                                                           0.54

Fall
                                                                            240
                                                                           0.90
                                                                           1.02
                                                                           0.12
                                                                           13.6
                                                                           0.72
                                                                           46.4
                                                                           0.69

Annual
                                                                            936
                                                                           0.90
                                                                           1.07
                                                                           0.17
                                                                           18.4
                                                                           1.07
                                                                           60.2
                                                                           0.42
                                     South
                                      CSN
Winter
                                                                            226
                                                                           2.19
                                                                           2.86
                                                                           0.67
                                                                           30.5
                                                                           2.08
                                                                           64.4
                                                                           0.55

Spring
                                                                            251
                                                                           1.57
                                                                           1.90
                                                                           0.33
                                                                           21.2
                                                                           1.15
                                                                           52.5
                                                                           0.55

Summer
                                                                            208
                                                                           1.68
                                                                           2.07
                                                                           0.39
                                                                           23.3
                                                                           1.45
                                                                           56.0
                                                                           0.55

Fall
                                                                            194
                                                                           2.31
                                                                           3.08
                                                                           0.77
                                                                           33.6
                                                                           2.62
                                                                           59.5
                                                                           0.58

Annual
                                                                            879
                                                                           1.92
                                                                           2.45
                                                                           0.53
                                                                           27.6
                                                                           1.87
                                                                           58.6
                                                                           0.57

                                    IMPROVE
Winter
                                                                            212
                                                                           0.74
                                                                           1.10
                                                                           0.36
                                                                           48.7
                                                                           1.25
                                                                           69.2
                                                                           0.63

Spring
                                                                            242
                                                                           1.01
                                                                           1.04
                                                                           0.02
                                                                            2.4
                                                                           1.76
                                                                           61.7
                                                                           0.51

Summer
                                                                            219
                                                                           1.09
                                                                           0.88
                                                                          -0.21
                                                                          -19.4
                                                                           0.67
                                                                           46.2
                                                                           0.73

Fall
                                                                            234
                                                                           1.11
                                                                           0.97
                                                                          -0.14
                                                                          -12.3
                                                                           0.63
                                                                           40.2
                                                                           0.73

Annual
                                                                            907
                                                                           0.99
                                                                           1.00
                                                                           0.00
                                                                            0.4
                                                                           1.19
                                                                           52.7
                                                                           0.52
                                   Southwest
                                      CSN
Winter
                                                                            180
                                                                           2.17
                                                                           3.03
                                                                           0.86
                                                                           39.5
                                                                           2.53
                                                                           74.8
                                                                           0.33

Spring
                                                                            194
                                                                           0.92
                                                                           1.49
                                                                           0.57
                                                                           62.2
                                                                           1.27
                                                                           83.2
                                                                           0.37

Summer
                                                                            179
                                                                           1.47
                                                                           1.38
                                                                          -0.09
                                                                           -6.1
                                                                           0.84
                                                                           37.9
                                                                           0.43

Fall
                                                                            187
                                                                           1.53
                                                                           2.02
                                                                           0.49
                                                                           32.1
                                                                           1.40
                                                                           67.9
                                                                           0.47

Annual
                                                                            740
                                                                           1.51
                                                                           1.97
                                                                           0.46
                                                                           30.5
                                                                           1.63
                                                                           65.7
                                                                           0.43

                                    IMPROVE
Winter
                                                                            829
                                                                           0.52
                                                                           0.50
                                                                          -0.02
                                                                           -4.3
                                                                           0.80
                                                                           48.1
                                                                           0.77

Spring
                                                                            909
                                                                           0.42
                                                                           0.46
                                                                           0.04
                                                                            8.5
                                                                           0.65
                                                                           55.6
                                                                           0.45

Summer
                                                                            894
                                                                           0.86
                                                                           0.62
                                                                          -0.24
                                                                          -27.6
                                                                           0.76
                                                                           50.4
                                                                           0.53

Fall
                                                                            882
                                                                           0.60
                                                                           0.50
                                                                          -0.10
                                                                          -16.2
                                                                           0.55
                                                                           46.5
                                                                           0.66

Annual
                                                                           3514
                                                                           0.60
                                                                           0.52
                                                                          -0.08
                                                                          -13.4
                                                                           0.70
                                                                           49.9
                                                                           0.62
                               N. Rockies &
                                    Plains
                                      CSN
Winter
                                                                            124
                                                                           1.05
                                                                           1.10
                                                                           0.05
                                                                            4.5
                                                                           1.93
                                                                           95.2
                                                                           0.12

Spring
                                                                            145
                                                                           0.87
                                                                           0.75
                                                                          -0.12
                                                                          -13.4
                                                                           0.76
                                                                           54.9
                                                                           0.48

Summer
                                                                            161
                                                                           1.45
                                                                           0.87
                                                                          -0.58
                                                                          -40.0
                                                                           1.05
                                                                           47.2
                                                                           0.49

Fall
                                                                            146
                                                                           1.01
                                                                           0.77
                                                                          -0.24
                                                                          -23.6
                                                                           1.04
                                                                           52.0
                                                                           0.23

Annual
                                                                            576
                                                                           1.11
                                                                           0.87
                                                                          -0.24
                                                                          -21.9
                                                                           1.24
                                                                           59.6
                                                                           0.25

                                    IMPROVE
Winter
                                                                            540
                                                                           0.30
                                                                           0.34
                                                                           0.05
                                                                           15.5
                                                                           0.42
                                                                           70.0
                                                                           0.36

Spring
                                                                            573
                                                                           0.59
                                                                           0.47
                                                                          -0.12
                                                                          -20.9
                                                                           1.33
                                                                           63.6
                                                                           0.55

Summer
                                                                            601
                                                                           1.22
                                                                           1.03
                                                                          -0.20
                                                                          -16.0
                                                                           3.17
                                                                           58.2
                                                                           0.25

Fall
                                                                            574
                                                                           0.63
                                                                           0.49
                                                                          -0.14
                                                                          -22.5
                                                                           1.05
                                                                           60.6
                                                                           0.23

Annual
                                                                           2288
                                                                           0.70
                                                                           0.59
                                                                          -0.11
                                                                          -15.3
                                                                           1.84
                                                                           61.1
                                                                           0.34
                                   Northwest
                                      CSN
Winter
                                                                            132
                                                                           2.54
                                                                           4.33
                                                                           1.80
                                                                           70.9
                                                                           4.33
                                                                           98.1
                                                                           0.45

Spring
                                                                            135
                                                                           1.43
                                                                           3.62
                                                                           2.19
                                                                          152.9
                                                                           4.59
                                                                          160.7
                                                                           0.58

Summer
                                                                            129
                                                                           1.55
                                                                           3.83
                                                                           2.28
                                                                          147.0
                                                                           3.58
                                                                          153.7
                                                                           0.48

Fall
                                                                            130
                                                                           1.99
                                                                           3.90
                                                                           1.92
                                                                           96.5
                                                                           3.53
                                                                          116.0
                                                                           0.48

Annual
                                                                            526
                                                                           1.88
                                                                           3.92
                                                                           2.05
                                                                          109.1
                                                                           4.04
                                                                          126.3
                                                                           0.45

                                    IMPROVE
Winter
                                                                            425
                                                                           0.36
                                                                           0.61
                                                                           0.25
                                                                           69.1
                                                                           1.54
                                                                          128.6
                                                                           0.57

Spring
                                                                            482
                                                                           0.54
                                                                           0.82
                                                                           0.28
                                                                           51.8
                                                                           1.81
                                                                           93.3
                                                                           0.53

Summer
                                                                            488
                                                                           1.32
                                                                           1.57
                                                                           0.24
                                                                           18.5
                                                                           2.94
                                                                           83.3
                                                                           0.47

Fall
                                                                            471
                                                                           0.77
                                                                           1.28
                                                                           0.51
                                                                           66.8
                                                                           2.43
                                                                          116.9
                                                                           0.55

Annual
                                                                           1866
                                                                           0.76
                                                                           1.08
                                                                           0.32
                                                                           42.3
                                                                           2.26
                                                                           98.6
                                                                           0.44
                                     West
                                      CSN
Winter
                                                                            241
                                                                           3.61
                                                                           4.10
                                                                           0.49
                                                                           13.6
                                                                           2.89
                                                                           48.9
                                                                           0.58

Spring
                                                                            253
                                                                           1.52
                                                                           1.85
                                                                           0.32
                                                                           21.3
                                                                           1.10
                                                                           44.5
                                                                           0.64

Summer
                                                                            247
                                                                           2.40
                                                                           2.23
                                                                          -0.17
                                                                           -7.2
                                                                           1.44
                                                                           36.0
                                                                           0.51

Fall
                                                                            235
                                                                           2.77
                                                                           3.10
                                                                           0.33
                                                                           11.9
                                                                           1.96
                                                                           43.7
                                                                           0.62

Annual
                                                                            976
                                                                           2.56
                                                                           2.80
                                                                           0.24
                                                                            9.4
                                                                           1.96
                                                                           43.8
                                                                           0.63

                                    IMPROVE
Winter
                                                                            510
                                                                           0.59
                                                                           0.52
                                                                          -0.07
                                                                          -12.0
                                                                           0.60
                                                                           50.5
                                                                           0.87

Spring
                                                                            546
                                                                           0.62
                                                                           0.51
                                                                          -0.11
                                                                          -17.5
                                                                           0.48
                                                                           46.7
                                                                           0.61

Summer
                                                                            556
                                                                           1.72
                                                                           1.39
                                                                          -0.33
                                                                          -19.2
                                                                           2.77
                                                                           52.4
                                                                           0.43

Fall
                                                                            527
                                                                           1.07
                                                                           1.00
                                                                          -0.07
                                                                           -6.7
                                                                           1.22
                                                                           50.0
                                                                           0.64

Annual
                                                                           2139
                                                                           1.01
                                                                           0.86
                                                                          -0.15
                                                                          -14.7
                                                                           1.58
                                                                           50.6
                                                                           0.54

 2A.2	Projecting PM2.5 DVs to 2032
PM2.5 DVs were projected to 2032 using air quality modeling to inform estimates of the emission reductions needed to meet standards beyond the reductions expected to occur due to finalized rules. The projections were performed by pairing the 2016 CMAQ simulation with a corresponding CMAQ simulation based on emissions representative of 2032. The 2032 emissions case accounts for factors including emission reductions between 2016 and 2032 from `on-the-books' rules and has been described in detail previously (USEPA, 2022). Other than differences in the emissions inputs, all aspects of the 2032 CMAQ modeling were specified identical to the 2016 modeling. These aspects include the meteorology, boundary conditions, the 12-km modeling domain, and the model configuration.
To predict the influence of the emission reductions between 2016 and 2032 on PM2.5 DVs, PM2.5 relative response factors (RRFs) were calculated using the CMAQ results to project monitoring data to 2032. RRFs are the ratios of modeled PM2.5 species concentrations in the future year (2032) to the base year (2016). RRFs are used in projecting air quality to help mitigate the influence of systematic biases in model predictions (e.g., systematic biases in the 2016 and 2032 modeling may partially cancel in the ratio) (Cohan and Chen, 2014, NRC, 2004, USEPA, 2018). RRFs are calculated for each PM2.5 component (i.e., sulfate, nitrate, organic carbon, elemental carbon, crustal material, and ammonium). The annual and 24-hour PM2.5 DVs for the future year are calculated by applying the species-specific RRFs to ambient PM2.5 concentrations from the PM2.5 monitoring network, which are disaggregated into species concentrations by applying the SANDWICH method (Frank, 2006) and through interpolation of PM2.5 species data from the CSN and IMPROVE monitoring networks. Details on the PM2.5 projection method using RRFs are provided in the user's guide for the predecessor to the SMAT-CE software (Abt, 2014). The RRF method for calculating future-year PM2.5 annual and 24-hour PM2.5 DVs was implemented here using the Software for Modeled Attainment Test-Community Edition (SMAT-CE) version 1.8 (USEPA, 2018, Wang et al., 2015).
    2A.2.1	Monitoring Data for PM2.5 Projections
PM2.5 DVs were projected using ambient PM2.5 measurements from the 2014-2018 period centered on the 2016 CMAQ modeling period. PM2.5 species measurements from the IMPROVE and CSN networks during 2015 - 2017 were used to disaggregate the measured total PM2.5 concentrations into components for the RRF calculations. As in the 2012 PM2.5 NAAQS RIA (USEPA, 2012a), limited exclusion of wildfire and fireworks influence on PM2.5 concentrations was applied to the 2014-2018 PM2.5 monitoring data in addition to exclusion of EPA-concurred exceptional events. Monitoring data were evaluated (i.e., screened) for potential wildfire and fireworks influence because PM2.5 concentrations may be influenced by atypical, extreme, or unrepresentative events such as wildfires or fireworks that may be appropriate for exclusion as described in EPA's memorandum Additional Methods, Determinations, and Analyses to Modify Air Quality Data Beyond Exceptional Events (USEPA, 2019a). Due to the challenges in identifying wildfire influence on monitored concentrations, only limited screening of major wildfire influence is possible here, and wildfire impacts on concentrations likely persists in the screened data.
 The steps in implementing the limited screening of major wildfire and fireworks influence on PM2.5 concentrations are as follows:
 An extreme value cutoff of 61 ug m[-3] was identified based the 99.9[th] percentile value from all daily PM2.5 concentrations across all sites in the long-term AQS observations (2002-2018).
 Specific states and months were screened for instances of monitors exceeding the extreme value cutoff to identify potential periods of interest. States included for screening were CA, WA, OR, MT, ID, and CO. These states were selected due to the prevalence of wildfire in the western U.S. and the potential for NAAQS exceedances in these areas. States in the southwest were not included in part due to challenges in distinguishing wildfire influence from dust events. Months included were June-October (while November can be a high fire month for parts of the western U.S., it becomes more difficult to distinguish wildfire PM2.5 from residential wood smoke and other anthropogenic sources during the late fall).
 For periods flagged under the previous step, the presence of visible wildfire smoke was corroborated using satellite imagery from NASA's Worldview platform (https://worldview.earthdata.nasa.gov) for the dates and geographic location identified. If corroboration with satellite imagery was not possible, the episode was not included. Timeseries for individual sites flagged were also examined to confirm PM2.5 enhancements temporally consistent with the wildfire events identified (Figures 2A-16 to 2A-25).
 For wildfire periods confirmed with satellite imagery, all concentrations above the extreme value cutoff of 61 ug m[-3] occurring during the identified wildfire episode window at impacted sites were removed.
 In addition to the evaluation criteria above, data corresponding to the Camp Fire (northern CA during November 2018) and the Appalachian Fires (NC, TN, GA during November 2016) were evaluated for exclusion if concentrations exceeded the extreme value threshold of 61 mg m[-3]. These large fire episodes show obvious impacts across multiple monitors and were clearly documented with satellite imagery (Figures 2A-6 to and 2A-15).
 In addition to the limited exclusion of major wildfire influence, data were evaluated to identify days for potential exclusion due to the influence of isolated fireworks events on PM2.5 concentrations. The 99.9[th] percentile value of 61 ug m[-3] was applied as the cutoff across all sites for New Year's Eve and the Fourth of July.
A full list of episodes and counties that were evaluated for potential exclusion of monitor data due to influence from wildfire and fireworks is shown in Table 2A-7. Example satellite imagery and timeseries of PM2.5 at impacted monitors for each episode are shown in Figures 2A-6 to 2A-14. The flagged day-site combinations represent 0.4% (767/200,201) of all possible day-site combinations for those sites. Not all days flagged for potential fire influence were excluded only those above the 61 ug m[-3] threshold.

Table 2A-7	Wildfire Episodes and Counties Where Data Were Screened for Exclusion if PM2.5 Concentrations Exceeded the Extreme Value Threshold of 61 ug m[-3]
Episode
Dates
Impacted County
State
Camp Fire
Nov. 8-20, 2018
Alameda
CA

Stanislaus
CA

San Joaquin
CA

Sonoma
CA

Butte
CA

Contra Costa
CA

Colusa
CA

Fresno
CA

Mendocino
CA

Sacramento
CA

Napa
CA

Solano
CA

Placer
CA

San Francisco
CA

Marin
CA

Yolo
CA

Tehama
CA

Lake
CA

Santa Clara
CA

Santa Cruz
CA

Nevada
CA

Kings
CA

Merced
CA

San Mateo
CA

Madera
CA

Monterey
CA
North Bay/Wine Country Fires
Oct. 8-20, 2017
Napa
CA

San Joaquin
CA

Mendocino
CA

Solano
CA

Contra Costa
CA

Lake
CA

Sonoma
CA

Marin
CA

Alameda
CA

Nevada
CA

Mendocino
CA
Pacific Northwest/northern CA Fires of 2017
Aug. 1- Sept. 13, 2017
Benewah
ID

Lemhi
ID

Shoshone
ID

Ada
ID

Canyon
ID

Bannock
ID

Jackson
OR

Lane
OR

Josephine
OR

Crook
OR

Klamath
OR

Harney
OR

Flathead
MT

Silver Bow
MT

Lewis and Clark
MT

Powder River
MT

Fergus
MT

Missoula
MT

Ravalli
MT

Lincoln
MT

Yakima
WA

Spokane
WA

Clark
WA

King
WA

Pierce
WA

Okanogan
WA

Snohomish
WA

Shasta
CA

Tehama
CA

Sonoma
CA

Siskiyou
CA
Washington/Oregon Fires of 2018
July 14-Aug. 25, 2018
Spokane
WA

Okanogan
WA

Skagit
WA

Whatcom
WA

Snohomish
WA

Kitsap
WA

King
WA

Clark
WA

Pierce
WA

Yakima
WA

Jackson
OR

Lake
OR

Harney
OR

Klamath
OR

Josephine
OR

Lane
OR

Siskiyou
CA
Montana Fires of 2018
Aug. 13-Aug. 28, 2018
Lincoln
MT

Missoula
MT

Lewis and Clark
MT

Yellowstone
MT

Fergus
MT

Flathead
MT

Shoshone
ID
Montana/Washington/Idaho Fires of 2015
Aug. 15-Aug. 30, 2015
Missoula
MT

Ravalli
MT

Lincoln
MT

Missoula
MT

Flathead
MT

Lewis and Clark
MT

Powder River
MT

Silver Bow
MT

Fergus
MT

Lemhi
ID

Shoshone
ID

Bannock
ID

Clark
WA
416/Burro Fire Complex
June 8-13 2018
La Plata
CO
Butte Fire
Sept. 11-14, 2015
Calaveras
CA

Placer
CA
Carr/Mendocino/Ferguson Fires
July 28-Aug. 18, 2018
Inyo
CA

Mono
CA

Shasta
CA

Siskiyou
CA

Calaveras
CA

Tehama
CA

Lake
CA

Fresno
CA

Tulare
CA

Butte
CA

Nevada
CA
Appalachian Fires
Nov. 7-24, 2016
Hamilton
TN

Knox
TN

Loudon
TN

Roane
TN

Blount
TN

Swain
NC

Mitchell
NC

Buncombe
NC

Jackson
NC

Walker
GA

Clarke
GA

Richmond
GA

Hall
GA

Greenville
SC

Richland
SC

Edgefield
SC

Lexington
SC

Charleston
SC
Fireworks
July 4-5 and Dec. 31-Jan. 1 (all years)
Weber
UT

Pierce
WA

Snohomish
WA

Clark
NV

St. Louis City
MO

Macomb
MI

Marion
IN

Lake
IN

Allen
IN

Cook
IL

La Plata
CO

Stanislaus
CA

San Joaquin
CA

San Bernardino
CA

Riverside
CA

Merced
CA

Madera
CA

Los Angeles
CA

Kings
CA

Kern
CA

Inyo
CA

Imperial
CA

Fresno
CA

Santa Cruz
AZ

Maricopa
AZ

Figure 2A-6	Visible Satellite Imagery from NASA's Worldview Platform Showing Smoke from the Camp Fire on 11/10/2018

Figure 2A-7	Visible Satellite Imagery from NASA's Worldview Platform Showing Smoke from the North Bay/Wine Country Fires on 10/09/2017

Figure 2A-8	Visible Satellite Imagery from NASA's Worldview Platform Showing Smoke from Fires Across the Pacific Northwest/Northern California on 08/29/2017

Figure 2A-9 	Visible Satellite Imagery from NASA's Worldview Platform Showing Smoke from Fires in Washington and Oregon on 08/09/2018

Figure 2A-10	Visible Satellite Imagery from NASA's Worldview Platform Showing Smoke from Fires in Montana on 08/19/2018

Figure 2A-11	Visible Satellite Imagery from NASA's Worldview Platform Showing Smoke from Fires in Montana, Washington and Idaho on 08/22/2015

Figure 2A-12	Visible Satellite Imagery from NASA's Worldview Platform Showing Smoke from the 416/Burro Complex Fires on 06/10/2018

Figure 2A-13	Visible Satellite Imagery from NASA's Worldview Platform Showing Smoke from the Butte Fire on 09/11/2015

Figure 2A-14	Visible Satellite Imagery from NASA's Worldview Platform Showing Smoke from the Carr/Mendocino/Ferguson Fires on 08/04/2018

Figure 2A-15	Visible Satellite Imagery from NASA's Worldview Platform Showing Smoke from Fires in the Appalachians on 11/10/2016

Figure 2A-16	Daily PM2.5 (in ug m[-3]) from a Subset of Monitors Impacted by the Camp Fire in November 2018
Note: Bottom axis shows day in 2018. Red line indicates extreme value threshold of 61 ug m[-3] used for screening.

Figure 2A-17	Daily PM2.5 (in ug m[-3]) from a Subset of Monitors Impacted by the North Bay/Wine Country Fires in October 2017
Note: Bottom axis shows day in 2017. Red line indicates extreme value threshold of 61 ug m[-3] used for screening.

Figure 2A-18	Daily PM2.5 (in ug m[-3]) from a Subset of Monitors Impacted by Fires in the Pacific Northwest/Northern California in August-September 2017
Note: Bottom axis shows day in 2017. Red line indicates extreme value threshold of 61 ug m[-3] used for screening.

Figure 2A-19	Daily PM2.5 (in ug m[-3]) from a Subset of Monitors Impacted by Fires in Washington and Oregon in July-August 2018
Note: Bottom axis shows day in 2018. Red line indicates extreme value threshold of 61 ug m[-3] used for screening.

Figure 2A-20 	Daily PM2.5 (in ug m[-3]) from the Monitors Impacted by Fires and Smoke in Montana in August 2018
Note: Bottom axis shows day in 2018. Red line indicates extreme value threshold of 61 ug m[-3] used for screening.

Figure 2A-21 	Daily PM2.5 (in ug m[-3]) from a Subset of Monitors Impacted by Fires in Montana, Washington and Idaho in August 2015
Note: Bottom axis shows day in 2015. Red line indicates extreme value threshold of 61 ug m[-3] used for screening.

Figure 2A-22	Daily PM2.5 (in ug m[-3]) from the Monitor in Plata, CO Impacted by the 416/Burro Fire Complex in June 2018
Note: Bottom axis shows day in 2018. Red line indicates extreme value threshold of 61 ug m[-3] used for screening.

Figure 2A-23	Daily PM2.5 (in ug m[-3]) from the Two monitors Impacted by the Butte Fire in September 2015
Note: Bottom axis shows day in 2015. Red line indicates extreme value threshold of 61 ug m[-3] used for screening.

Figure 2A-24	Daily PM2.5 (in ug m[-3]) from a Subset of Monitors Impacted by the Carr/Mendocino/Ferguson Fires in August 2018
Note: Bottom axis shows day in 2018. Red line indicates extreme value threshold of 61 ug m[-3] used for screening.

Figure 2A-25 	Daily PM2.5 (in ug m[-3]) from a Subset of Monitors Impacted by Fires in the Appalachians in November 2016
Note: Bottom axis shows day in 2016. Red line indicates extreme value threshold of 61 ug m[-3] used for screening.

    2A.2.2	Future-Year PM2.5 Design Values
PM2.5 DVs were projected to 2032 using air quality modeling as described above and compared with the existing standard combination, 12/35. Counties with projected 2032 PM2.5 DVs exceeding the existing standards are shown in Figure 2A-26. Counties that exceed only the 24-hour standard are in northern California, Oregon, Washington, Idaho, Utah, and Montana. Elevated PM2.5 episodically occurs in winter in these areas due to meteorological temperature inversions that concentrate PM2.5 in shallow layers, especially in mountainous terrain. In California, multiple counties exceed both the annual and 24-hour standards and three counties (Los Angeles, San Bernardino, and Imperial) exceed only the annual standard. Los Angeles and San Bernardino are in the South Coast Air Basin along with Riverside County, which exceeds both the annual and 24-hour standard.

Figure 2A-26	Counties with Projected 2032 PM2.5 DVs that Exceed the 24-Hour (24-hr Only), Annual (Annual Only) or Both the 24-Hour and Annual (Both) Standards for the Combination of Existing Standards (12/35)

As described below in section 2A.3.4, PM2.5 DVs for 2032 were adjusted to correspond with just meeting the existing standard level to form the 12/35 analytical baseline used in estimating the incremental costs and benefits of meeting the alternative standards relative to the existing standards. The county exceedances of the alternative standards in the 12/35 analytical baseline are shown in Figure 2A-27. Since the PM2.5 DVs have been adjusted to meet the 24-hour standard level of 35 g m[-3] in the analytical baseline, there are no exceedances of the 24-hour standard for the cases of 10/35, 9/35, and 8/35. For the 10/35 case, six counties in the east, three in the NW, and fifteen in California have annual PM2.5 DVs greater than 10 g m[-3] in the 12/35 analytical baseline. For the 10/30 case, twenty-three counties have 24-hr DVs greater than 30 g m-3 and annual DVs less than 10 g m[-3], and eleven counties exceed both the 24-hr and annual standards. For the 9/35 case, twenty-two counties exceed the annual standard in the eastern US, compared with six for the 10/35 and 10/30 cases. The total number of counties exceeding the standards increases from 51 to 141 when moving from 9/35 to 8/35. In Table 2A-8, PM2.5 DVs are shown for the 2032 projections and 12/35 analytical baseline for sites with the highest annual and 24-hour PM2.5 DVs in counties with 2032 DVs that exceed an annual standard 8 g m[-3] or a 24-hour standard of 30 g m[-3].

Figure 2A-27	Counties with PM2.5 DVs in the 12/35 Analytical Baseline that Exceed the 24-Hour (24-hr Only), Annual (Annual Only) or Both the 24-Hour and Annual (Both) Standards for the Combination of Existing Standards

Table 2A-8	PM2.5 DVs for 2032 Projection and 12/35 Analytical Baseline for the Highest DVs in the County for Counties with Annual 2032 DVs Greater 8 g m[-3] or 24-hour 2032 DVs Greater than 30 g m[-3]
State
County
                                    Annual
                                    2032 DV
                                 (g m[-3])
                                    24-hour
                                    2032 DV
                                 (g m[-3])
                                    Annual
                                   12/35 DV
                                 (g m[-3])
                                    24-hour
                                   12/35 DV
                                 (g m[-3])
AL
Jefferson
                                     9.86
                                     20.1
                                     9.86
                                     20.1
AL
Talladega
                                     8.20
                                     16.3
                                     8.20
                                     16.3
AZ
Maricopa
                                     9.47
                                     26.7
                                     9.47
                                     26.7
AZ
Pinal[a]
                                     8.16
                                     34.2
                                     8.16
                                     34.2
AZ
Santa Cruz
                                     8.99
                                     26.5
                                     8.99
                                     26.5
AR
Pulaski
                                     8.99
                                     19.3
                                     8.99
                                     19.3
AR
Union
                                     8.12
                                     17.0
                                     8.12
                                     17.0
CA
Alameda
                                     10.14
                                     25.4
                                     10.14
                                     25.4
CA
Butte
                                     8.28
                                     27.2
                                     8.28
                                     27.2
CA
Contra Costa
                                     9.16
                                     25.1
                                     9.16
                                     25.1
CA
Fresno
                                     13.34
                                     50.8
                                     11.43
                                     35.4
CA
Imperial
                                     12.45
                                     32.4
                                     12.04
                                     31.5
CA
Kern
                                     16.20
                                     57.2
                                     12.04
                                     32.5
CA
Kings
                                     15.27
                                     48.2
                                     12.04
                                     28.4
CA
Los Angeles
                                     12.73
                                     34.9
                                     12.04
                                     31.1
CA
Madera
                                     12.13
                                     39.8
                                     10.60
                                     31.1
CA
Marin
                                     8.18
                                     23.4
                                     8.18
                                     23.4
CA
Merced
                                     11.88
                                     36.3
                                     10.79
                                     29.1
CA
Napa
                                     10.09
                                     25.7
                                     10.09
                                     25.7
CA
Orange
                                     7.79
                                     31.5
                                     7.47
                                     28.5
CA
Plumas
                                     14.52
                                     47.8
                                     10.60
                                     35.4
CA
Riverside
                                     14.10
                                     39.9
                                     12.04
                                     33.1
CA
Sacramento
                                     9.29
                                     31.0
                                     9.29
                                     31.0
CA
San Bernardino
                                     14.96
                                     35.0
                                     12.04
                                     26.3
CA
San Diego
                                     9.16
                                     22.3
                                     9.16
                                     22.3
CA
San Joaquin
                                     12.01
                                     35.7
                                     10.08
                                     29.1
CA
San Luis Obispo
                                     9.63
                                     25.1
                                     9.63
                                     25.1
CA
Santa Clara
                                     9.56
                                     26.0
                                     9.56
                                     26.0
CA
Siskiyou
                                     7.77
                                     34.8
                                     7.77
                                     34.8
CA
Solano
                                     9.04
                                     24.7
                                     9.04
                                     24.7
CA
Stanislaus
                                     12.43
                                     38.7
                                     11.08
                                     29.8
CA
Sutter
                                     8.82
                                     27.6
                                     8.82
                                     27.6
CA
Tulare
                                     14.66
                                     46.5
                                     12.04
                                     25.3
CA
Ventura
                                     9.23
                                     33.5
                                     9.23
                                     33.5
CO
Denver
                                     9.04
                                     24.1
                                     9.04
                                     24.1
CO
Weld
                                     8.14
                                     24.9
                                     8.14
                                     24.9
DE
New Castle
                                     8.14
                                     21.4
                                     8.14
                                     21.4
DC
District of Columbia
                                     8.21
                                     19.8
                                     8.21
                                     19.8
GA
Bibb
                                     8.80
                                     18.3
                                     8.80
                                     18.3
GA
Clayton
                                     8.57
                                     17.2
                                     8.57
                                     17.2
GA
Cobb
                                     8.09
                                     16.6
                                     8.09
                                     16.6
GA
DeKalb
                                     8.08
                                     18.2
                                     8.08
                                     18.2
GA
Dougherty
                                     8.38
                                     21.3
                                     8.38
                                     21.3
GA
Floyd
                                     8.72
                                     17.3
                                     8.72
                                     17.3
GA
Fulton
                                     9.46
                                     20.4
                                     9.46
                                     20.4
GA
Gwinnett
                                     8.06
                                     18.7
                                     8.06
                                     18.7
GA
Muscogee
                                     8.68
                                     27.3
                                     8.68
                                     27.3
GA
Richmond
                                     8.54
                                     21.0
                                     8.54
                                     21.0
GA
Wilkinson
                                     8.97
                                     19.2
                                     8.97
                                     19.2
ID
Benewah
                                     9.61
                                     35.2
                                     9.61
                                     35.2
ID
Canyon
                                     8.86
                                     31.4
                                     8.86
                                     31.4
ID
Lemhi
                                     11.03
                                     39.4
                                     10.05
                                     35.4
ID
Shoshone
                                     11.04
                                     36.6
                                     10.75
                                     35.4
IL
Cook
                                     9.43
                                     20.7
                                     9.43
                                     20.7
IL
Madison
                                     9.03
                                     19.0
                                     9.03
                                     19.0
IL
Saint Clair
                                     8.99
                                     17.6
                                     8.99
                                     17.6
IN
Allen
                                     8.10
                                     19.6
                                     8.10
                                     19.6
IN
Clark
                                     8.58
                                     19.8
                                     8.58
                                     19.8
IN
Elkhart
                                     8.37
                                     23.5
                                     8.37
                                     23.5
IN
Floyd
                                     8.08
                                     18.0
                                     8.08
                                     18.0
IN
Lake
                                     8.92
                                     22.2
                                     8.92
                                     22.2
IN
Marion
                                     9.61
                                     22.0
                                     9.61
                                     22.0
IN
St. Joseph
                                     8.72
                                     20.4
                                     8.72
                                     20.4
IN
Vanderburgh
                                     8.40
                                     17.5
                                     8.40
                                     17.5
IN
Vigo
                                     8.47
                                     19.2
                                     8.47
                                     19.2
KS
Wyandotte
                                     8.15
                                     19.9
                                     8.15
                                     19.9
KY
Jefferson
                                     8.85
                                     19.5
                                     8.85
                                     19.5
LA
Caddo
                                     9.44
                                     19.6
                                     9.44
                                     19.6
LA
East Baton Rouge
                                     8.69
                                     20.7
                                     8.69
                                     20.7
LA
Iberville
                                     8.06
                                     18.6
                                     8.06
                                     18.6
LA
St. Bernard
                                     8.11
                                     17.4
                                     8.11
                                     17.4
LA
West Baton Rouge
                                     8.67
                                     18.7
                                     8.67
                                     18.7
MD
Howard
                                     8.21
                                     18.6
                                     8.21
                                     18.6
MD
Baltimore (City)
                                     8.17
                                     21.5
                                     8.17
                                     21.5
MI
Kent
                                     8.49
                                     22.5
                                     8.49
                                     22.5
MI
Wayne
                                     10.06
                                     24.1
                                     10.06
                                     24.1
MS
Hinds
                                     8.08
                                     18.1
                                     8.08
                                     18.1
MO
Buchanan
                                     8.15
                                     17.1
                                     8.15
                                     17.1
MO
Jackson
                                     8.09
                                     18.1
                                     8.09
                                     18.1
MO
Jefferson
                                     8.51
                                     18.4
                                     8.51
                                     18.4
MO
Saint Louis
                                     8.82
                                     19.1
                                     8.82
                                     19.1
MO
St. Louis City
                                     8.36
                                     19.8
                                     8.36
                                     19.8
MT
Lewis and Clark
                                     8.57
                                     37.6
                                     8.03
                                     35.4
MT
Lincoln
                                     11.08
                                     33.2
                                     11.08
                                     33.2
MT
Missoula
                                     9.53
                                     29.6
                                     9.53
                                     29.6
MT
Ravalli
                                     8.75
                                     38.0
                                     8.11
                                     35.4
MT
Silver Bow
                                     8.64
                                     30.6
                                     8.64
                                     30.6
NE
Douglas
                                     8.08
                                     17.8
                                     8.08
                                     17.8
NE
Sarpy
                                     8.10
                                     17.5
                                     8.10
                                     17.5
NV
Clark
                                     9.24
                                     23.0
                                     9.24
                                     23.0
NJ
Camden
                                     9.21
                                     22.3
                                     9.21
                                     22.3
NJ
Union
                                     8.62
                                     21.3
                                     8.62
                                     21.3
NM
Dona Ana
                                     8.57
                                     27.6
                                     8.57
                                     27.6
NY
New York
                                     8.95
                                     22.1
                                     8.95
                                     22.1
NC
Davidson
                                     8.29
                                     18.1
                                     8.29
                                     18.1
NC
Mecklenburg
                                     8.15
                                     17.5
                                     8.15
                                     17.5
NC
Wake
                                     8.12
                                     16.7
                                     8.12
                                     16.7
OH
Butler
                                     9.82
                                     20.7
                                     9.82
                                     20.7
OH
Cuyahoga
                                     10.23
                                     21.8
                                     10.23
                                     21.8
OH
Franklin
                                     8.17
                                     17.9
                                     8.17
                                     17.9
OH
Hamilton
                                     8.91
                                     20.1
                                     8.91
                                     20.1
OH
Jefferson
                                     9.26
                                     22.3
                                     9.26
                                     22.3
OH
Lucas
                                     8.70
                                     19.4
                                     8.70
                                     19.4
OH
Mahoning
                                     8.20
                                     19.0
                                     8.20
                                     19.0
OH
Stark
                                     8.92
                                     19.9
                                     8.92
                                     19.9
OH
Summit
                                     8.72
                                     19.9
                                     8.72
                                     19.9
OK
Tulsa
                                     8.13
                                     19.5
                                     8.13
                                     19.5
OR
Crook
                                     8.29
                                     35.5
                                     8.27
                                     35.4
OR
Harney
                                     8.61
                                     30.8
                                     8.61
                                     30.8
OR
Jackson
                                     9.18
                                     17.3
                                     9.18
                                     17.3
OR
Klamath
                                     8.64
                                     31.2
                                     8.64
                                     31.2
OR
Lake
                                     7.89
                                     37.3
                                     7.42
                                     35.4
OR
Lane
                                     8.12
                                     29.0
                                     8.12
                                     29.0
PA
Allegheny
                                     11.19
                                     34.7
                                     11.19
                                     34.7
PA
Armstrong
                                     9.28
                                     19.3
                                     9.28
                                     19.3
PA
Beaver
                                     8.44
                                     19.1
                                     8.44
                                     19.1
PA
Berks
                                     8.18
                                     23.9
                                     8.18
                                     23.9
PA
Cambria
                                     9.08
                                     22.8
                                     9.08
                                     22.8
PA
Chester
                                     8.97
                                     22.1
                                     8.97
                                     22.1
PA
Dauphin
                                     8.37
                                     24.5
                                     8.37
                                     24.5
PA
Delaware
                                     9.96
                                     23.6
                                     9.96
                                     23.6
PA
Lackawanna
                                     8.07
                                     18.6
                                     8.07
                                     18.6
PA
Lancaster
                                     10.14
                                     26.8
                                     10.14
                                     26.8
PA
Lebanon
                                     9.10
                                     27.1
                                     9.10
                                     27.1
PA
Lehigh
                                     8.17
                                     21.0
                                     8.17
                                     21.0
PA
Mercer
                                     8.42
                                     19.6
                                     8.42
                                     19.6
PA
Philadelphia
                                     9.75
                                     22.7
                                     9.75
                                     22.7
PA
Washington
                                     8.37
                                     19.0
                                     8.37
                                     19.0
PA
York
                                     8.56
                                     21.4
                                     8.56
                                     21.4
RI
Providence
                                     8.27
                                     17.9
                                     8.27
                                     17.9
SC
Greenville
                                     8.16
                                     18.6
                                     8.16
                                     18.6
TN
Davidson
                                     8.17
                                     16.9
                                     8.17
                                     16.9
TN
Knox
                                     8.60
                                     19.3
                                     8.60
                                     19.3
TX
Cameron
                                     9.75
                                     24.5
                                     9.75
                                     24.5
TX
Dallas
                                     8.08
                                     17.1
                                     8.08
                                     17.1
TX
El Paso
                                     9.08
                                     23.8
                                     9.08
                                     23.8
TX
Harris
                                     10.37
                                     22.0
                                     10.37
                                     22.0
TX
Hidalgo
                                     10.29
                                     25.8
                                     10.29
                                     25.8
TX
Nueces
                                     9.03
                                     23.9
                                     9.03
                                     23.9
TX
Travis
                                     9.07
                                     18.8
                                     9.07
                                     18.8
UT
Box Elder
                                     6.51
                                     31.7
                                     6.51
                                     31.7
UT
Cache
                                     7.07
                                     32.7
                                     7.07
                                     32.7
UT
Davis
                                     7.27
                                     31.1
                                     7.27
                                     31.1
UT
Salt Lake
                                     8.20
                                     37.4
                                     7.71
                                     35.4
UT
Utah
                                     7.63
                                     31.5
                                     7.63
                                     31.5
UT
Weber
                                     7.99
                                     30.8
                                     7.99
                                     30.8
WA
King
                                     8.31
                                     26.5
                                     8.31
                                     26.5
WA
Kittitas
                                     7.37
                                     38.0
                                     6.73
                                     35.4
WA
Okanogan
                                       -
                                     31.8
                                       -
                                     31.8
WA
Snohomish
                                     7.07
                                     31.3
                                     7.07
                                     31.3
WA
Spokane
                                     8.18
                                     27.2
                                     8.18
                                     27.2
WA
Yakima
                                     8.18
                                     38.8
                                     7.34
                                     35.4
WV
Berkeley
                                     8.21
                                     22.1
                                     8.21
                                     22.1
WV
Brooke
                                     8.41
                                     19.8
                                     8.41
                                     19.8
WV
Marshall
                                     8.46
                                     19.7
                                     8.46
                                     19.7
a The Hidden Valley site in Pinal County (04-021-3015) was not compared with the annual NAAQS in this analysis because it is a replacement site for the Cowtown Road site that was not comparable to the annual NAAQS (PCAQCD, 2020).

 2A.3	Developing Air Quality Ratios and Estimating Emission Reductions
As in the RIAs for the 2012 PM2.5 NAAQS review (USEPA, 2012a, USEPA, 2012b), air quality ratios are used here to estimate the emission reductions beyond the 2032 modeling case that are needed to meet the existing and alternative standards. Air quality ratios are developed from sensitivity modeling with CMAQ and relate a change in PM2.5 DV to a change in emissions. Air quality ratios have units of g m[-3] per kton of emissions. The remainder of this section describes the development of air quality ratios and their application to estimating emission reductions for meeting the existing and alternative standards.
    2A.3.1	Developing Air Quality Ratios for Primary PM2.5 Emissions
To develop air quality ratios that relate the change in DV in a county to the change in primary PM2.5 emissions in that county, CMAQ sensitivity modeling was performed with reductions in primary PM2.5 emissions in selected counties. The modeling was conducted using CMAQ version 5.2.1 for a 2028 modeling case similar to that of recent regional haze modeling (USEPA, 2019b) due to the availability of the 2028 (but not 2032) modeling platform at the time of the work.
To develop air quality ratios for primary PM2.5 emissions, a 2028 CMAQ sensitivity simulation was conducted with 50% reductions in primary PM2.5 emissions from anthropogenic sources in counties with annual 2028 DVs greater than 8 g m[-3] (Figure 2A-28). The change in annual and 24-hour PM2.5 DVs in these counties was then divided by the change in emissions in the respective counties to determine the air quality ratio at individual monitors as follows:
      AQratioPM2.5,i,j=∆DVi∆EmissCtyjx1000			(2A-1)
where DV is the change in design value (g m[-3]) between the 2028 base case and the simulation with 50% reduction in primary PM2.5 emissions at a monitor i in a county j, EmissCty is the change in primary PM2.5 emissions (tons) in county j between the 2028 base case and the simulation with 50% reduction in primary PM2.5 emissions, and the factor of 1000 converts units from (g m[-3] per ton) to (g m[-3] per kton).

Figure 2A-28	Counties with 50% Reduction in Anthropogenic Primary PM2.5 Emissions in 2028 Sensitivity Modeling

Representative air quality ratios for regions of the US were developed from the ratios at individual monitors as in the 2012 PM - 2.5 NAAQS review (USEPA, 2012b). Regional ratios were calculated as the 75[th] percentile of air quality ratios at monitors within five regions: Northeast, Southeast, Northern California, Southern California, and West (Figure 2A-29). The Northeast region was defined by combining the Upper Midwest, Ohio Valley, and Northeast US climate regions (Figure 2A-2); the Southeast region was defined by combining the Southeast and South climate regions (Figure 2A-2); and California was separated into Southern and Northern regions as done previously (USEPA, 2012b). The air quality ratios for primary PM2.5 emissions used in estimating the emission reductions needed to just meet standards are listed in Table 2A-9.

Figure 2A-29	Regional Groupings for Calculating Air Quality Ratios

Table 2A-9	Annual and 24-Hour Air Quality Ratios for Primary PM2.5 Emissions
Region
                           Annual Air Quality Ratio
                             (g m[-3] per kton)
                           24-hour Air Quality Ratio
                             (g m[-3] per kton)
Northeast
                                     1.37
                                     4.33
Southeast
                                     1.22
                                     3.51
West
                                     2.14
                                     8.70
Northern California
                                     3.15
                                     9.97
Southern California
                                     1.18
                                     2.56

The air quality ratios in Table 2A-9 relate the change in DV in a given county to a change in emissions in that county. The ratios are developed for local spatial scales because concentrations are most responsive to changes in local emissions. However, emission controls may not always be identified in the local county, and emission reductions in neighboring counties may sometimes be appropriate, such as in the eastern US where counties are relatively small, and terrain is relatively flat. To apply emission reductions in the neighboring counties in the eastern US, the responsiveness of annual PM2.5 DVs to emission reductions within a county was compared with the responsiveness for neighboring counties as estimated from the 2028 sensitivity modeling.
First, county groups of most relevance were identified from the 2028 sensitivity modeling. These groups were selected as eastern counties where emission reductions were applied and whose neighbors were not also neighbors of another county where emission reductions were applied. This set of county groups was then subset from the full list of counties and filtered to ensure that at least one monitor was included in the neighbor counties for the county group. The resulting county groups are shown in Figure 2A-30. The average relative responsiveness of annual DVs in the east for emission reductions in a core county to reductions in a neighboring county was then calculated as follows:
      ImpactRatio=mean(∆DVcore)mean(∆DVneighbor)=4			(2A-2)
where the numerator is the average impact on annual PM2.5 DVs in the core counties with 50% reduction in anthropogenic primary PM2.5 emissions, and the denominator is the average impact on annual PM2.5 DVs in neighboring counties. The resulting impact ratio suggests that primary PM2.5 emission reductions in neighboring counties would be 4x less effective as in the core county.

Figure 2A-30	Counties Used in Estimating the Relative Impact of Emissions in Core and Neighboring Counties

    2A.3.2	Developing Air Quality Ratios for NOx in Southern California
As described above, PM2.5 DVs exceeded the existing standards at monitors in the South Coast Air Basin in the 2032 modeling case. PM2.5 DVs were adjusted to meet the existing standards in these counties in creating the 12/35 analytical baseline. Since concentrations of ammonium nitrate are elevated in South Coast, NOx emission reductions were applied in these counties in addition to primary PM2.5 emission reductions to meet 12/35. For this purpose, air quality ratios were developed that relate a change in PM2.5 DVs to a change in NOx emissions at monitors in Southern California.
The air quality ratios were developed from a CMAQ sensitivity simulation with 50% reductions in anthropogenic NOx emissions relative to the 2028 modeling case. The 50% emission reductions were applied in counties with annual 2028 DVs greater than 8 g m[-3] and their neighboring counties (Figure 2A-31). The change in annual and 24-hour DVs in these counties was then divided by the change in emissions in the respective county groups to determine the air quality ratio at individual monitors as follows:
            AQratioPM2.5,i,j=∆DVi∆EmissCtyGroupjx1000			(2A-3)
where DV is the change in design value (g m[-3]) between the 2028 base case and the simulation with 50% reduction in NOx emissions at monitor i, EmissCtyGroup is the change in NOx emissions (ton) in the county group associated with county j between the 2028 base case and the simulation with 50% reduction in NOx emissions, and the factor of 1000 converts units from (g m[-3] per ton) to (g m[-3] per kton).

Figure 2A-31	Counties with 50% Reduction in Anthropogenic NOx Emissions in 2028 Sensitivity Modeling

The county groups for determining the emission change to associate with the DV change in Equation 2A-3 are defined in Table 2A-10. These county groups were identified by first selecting the county of focus plus the neighboring counties to reflect the regional nature of ammonium nitrate formation from NOx emissions. These county groups were then refined to account for the influence of terrain, which limits air mixing between different air basins, on meteorology and air pollution. For instance, although Kern County neighbors Los Angeles County, Kern is part of the SJV air basin while Los Angeles is part of the South Coast Air Basin. Kern is therefore not included in the county group associated with Los Angeles County, because Kern is separated from Los Angeles County by mountain ranges.
Table 2A-10	County Groups for Calculating Air Quality Ratios for NOx Emission Changes in Southern California
FIPS
County
County Group
06025
Imperial
Imperial; San Diego
06037
Los Angeles
Los Angeles; Orange; San Bernardino; Ventura
06065
Riverside
Riverside; Orange; San Bernardino
06071
San Bernardino
San Bernardino; Los Angeles; Orange; Riverside
06073
San Diego
San Diego; Imperial; Orange
06111
Ventura
Ventura; Los Angeles; Santa Barbara
To develop representative air quality ratios (USEPA, 2012b) for Southern California, the 75[th] percentile of the air quality ratios for individual monitors in the six counties in Table 2A-10 was calculated. The resulting air quality ratio for the annual standard is 0.004 g m[-3] per kton and for the 24-hour standard ratio is 0.038 g m[-3] per kton. These ratios were applied to adjust 2032 PM2.5 DVs according to 75% reductions in anthropogenic NOx emissions for counties in South Coast Air Basin (i.e., LA, San Bernardino, Riverside, and Orange). The 75% reduction in emissions corresponded to 78,700 tons. The 2032 DVs and the NOx-adjusted DVs are shown in Table 2A-11 for the highest annual and 24-hour DV monitors in the county. Note that these emission reductions were applied in meeting the existing standards (12/35) and are therefore not part of the incremental cost and benefits of meeting alternative standards relative to the existing standards.
Table 2A-11	2032 PM2.5 DVs and NOx-adjusted PM2.5 DVs for the Highest Annual and 24-Hour DV Monitors in South Coast Counties
Site ID
County
                                   AQ Ratio
                                    Annual
                              (g m-3 per kton)
                                   AQ Ratio
                                    24-hour
                              (g m-3 per kton)
                                    2032 DV
                                    Annual
                                 (g m[-3])
                                    2032 DV
                                    24-hour
                                 (g m[-3])
                                  NOx-Adj DV
                                    Annual
                                 (g m[-3])
                                  NOx-Adj DV
                                    24-hour
                                 (g m[-3])
060371302
Los Angeles
                                     0.004
                                     0.038
                                     12.38
                                     34.9
                                     12.06
                                     31.9
060374008
Los Angeles
                                     0.004
                                     0.038
                                     12.73
                                     31.0
                                     12.41
                                     28.0
060592022
Orange
                                     0.004
                                     0.038
                                     7.79
                                     14.6
                                     7.47
                                     11.6
060590007
Orange
                                     0.004
                                     0.038
                                       -
                                     31.5
                                       -
                                     28.5
060658005
Riverside
                                     0.004
                                     0.038
                                     14.10
                                     39.9
                                     13.78
                                     36.9
060710027
San Bernardino
                                     0.004
                                     0.038
                                     14.96
                                     35.0
                                     14.64
                                     32.0

    2A.3.3	Developing Air Quality Ratios for NOx in SJV, CA
As in the South Coast Air Basin, PM2.5 DVs exceed existing standards in SJV in the 2032 modeling case, and concentrations of ammonium nitrate are elevated in SJV. To develop PM2.5 DVs for SJV counties in the 12/35 analytical baseline, NOx emission reductions were applied in addition to primary PM2.5 emission reductions. To develop air quality ratios for NOx emission changes in SJV, information was used from Appendix K of the 2018 SJV PM2.5 Plan (SJVAPCD, 2018). The Plan was based on fine-scale CMAQ modeling and provides useful information for characterizing the responsiveness of PM2.5 DVs to NOx emissions.
The California Air Resources Board (CARB) modeled PM2.5 concentrations in SJV corresponding to 30% reductions in NOx emissions relative to a 2024 base case. The change in annual and 24-hour PM2.5 DVs at monitors in SJV was reported for the sensitivity simulation. Using this information, along with PM2.5 DVs and emissions information from the 2032 CMAQ modeling developed here, air quality ratios were calculated at monitors in SJV from the following equation:
      AQratioi=%Chg. DVi%Chg.EmisionSJVCARBDViEmissionSJV2032		(2A-4)
The parenthesis labeled CARB indicates values from the SJV Plan, and the parenthesis labeled 2032 indicates values from the 2032 CMAQ modeling described above. %Chg.DVi indicates the percent change in the design value for a given monitor, i, from Table 49 and 50 of Appendix K of the SJV Plan (SJVAPCD, 2018). %Chg.DVi ranged from 2.3% to 7.5% for annual DVs and from 7.0% to 16.3% for 24-hour DVs. %Chg.EmissionSJV indicates the percent change in NOx emissions in SJV and equaled 30%. DVi corresponds to the design value at monitor i, and EmissionSJV corresponds to the anthropogenic NOx emissions in SJV (i.e., 53,500 ton) in the 2032 CMAQ modeling developed here. Equation 2A-4 normalizes the percent changes from CARB's 2024 modeling to the PM2.5 DVs and emissions from the 2032 case for application here.
Air quality ratios were calculated as above for all monitors in SJV, except for the Tranquility monitor. The Tranquility monitor is in the Western part of Fresno County, away from the urban exceedance monitors, and has a low PM2.5 concentration (e.g., 2024 annual DV for CARB modeling is 5.6 g m[-3]). To develop representative air quality ratios for counties in SJV, the 75[th] percentile of air quality ratios over monitors in the SJV counties was calculated. These ratios were applied to adjust 2032 PM2.5 DVs according to 75% reductions in anthropogenic NOx emissions for counties in SJV. The 75% reduction in emissions corresponded to 40,200 tons. The 2032 DVs and the NOx-adjusted DVs are shown in Table 2A-12 for the highest annual and 24-hour DV monitors in the county. Note that these emission reductions were applied in meeting the existing standards (12/35) and are therefore not part of the incremental cost and benefits of meeting alternative standards relative to the existing standards.
Table 2A-12	2032 PM2.5 DVs and NOx-adjusted PM2.5 DVs for the Highest Annual and 24-Hour DV Monitors in SJV Counties
Site ID
County
                                   AQ Ratio
                                    Annual
                              (g m-3 per kton)
                                   AQ Ratio
                                    24-hour
                              (g m-3 per kton)
                                    2032 DV
                                    Annual
                                 (g m[-3])
                                    2032 DV
                                    24-hour
                                 (g m[-3])
                                  NOx-Adj DV
                                    Annual
                                 (g m[-3])
                                  NOx-Adj DV
                                    24-hour
                                 (g m[-3])
060190011
Fresno
                                     0.033
                                     0.337
                                     13.25
                                     50.8
                                     11.94
                                     37.3
060195025
Fresno
                                     0.033
                                     0.337
                                     13.34
                                     48.3
                                     12.03
                                     34.8
060290010
Kern
                                     0.041
                                     0.418
                                     14.40
                                     57.2
                                     12.74
                                     40.4
060290016
Kern
                                     0.041
                                     0.418
                                     16.20
                                     56.3
                                     14.54
                                     39.5
060311004
Kings
                                     0.072
                                     0.467
                                     15.27
                                     48.2
                                     12.37
                                     29.5
060392010
Madera
                                     0.038
                                     0.216
                                     12.13
                                     39.8
                                     10.60
                                     31.1
060470003
Merced
                                     0.027
                                     0.178
                                     11.88
                                     36.3
                                     10.79
                                     29.1
060771002
San Joaquin
                                     0.048
                                     0.164
                                     12.01
                                     35.7
                                     10.08
                                     29.1
060990006
Stanislaus
                                     0.034
                                     0.222
                                     12.43
                                     38.7
                                     11.08
                                     29.8
061072002
Tulare
                                     0.047
                                     0.472
                                     14.66
                                     46.5
                                     12.76
                                     27.6

    2A.3.4	Applying Air Quality Ratios to Estimate Emission Reductions
The emissions reductions needed to just meet standards were estimated using the primary PM2.5 air quality ratios in combination with the required incremental change in concentration. The emission reductions required to meet the DV target for a standard were calculated as follows:
      ∆Emissionstd=DVModel,std-DVTarget,stdAQratiostdx1000			(2A-5)
where Emissionstd is the emission reduction required to meet an annual or 24-hour standard; DVTarget,std is the level of the annual or 24-hour standard to be met; DVModel,std is the modeled PM2.5 DV for the annual or 24-hour standard at the county highest monitor; AQratiostd is the air quality ratio for that standard; and the factor of 1000 converts units from kton to ton.
For example, the highest 2032 annual PM2.5 DV in Kern County is 14.54 g m[-3] at site 06-029-0016 after applying the 75% NOx emission reduction to the 2032 DVs. The annual air quality ratio for primary PM2.5 emissions in Northern California is 3.15 g m[-3] per kton. Therefore, to meet an annual standard of 12 g m[-3], a total of 794 tons of primary PM2.5 emissions would be needed (i.e., (14.54-12.04)/3.15 x 1000). The highest 2032 24-hour PM2.5 DV in Kern County is 40.4 g m[-3] at site 06-029-0010 after applying the 75% NOx emission reduction to the 2032 DVs. The 24-hour air quality ratio for primary PM2.5 emissions in Northern California is 9.97 g m[-3] per kton. Therefore, to meet a 24-hour standard of 35 g m[-3], a total of 502 tons of primary PM2.5 emissions would be needed (i.e., (40.4-35.4)/9.97 x 1000). To determine the emission reductions needed to meet an annual and 24-hour standard combination, the maximum needed emissions across standards is calculated as follows:
      ∆Emissionstd.combo=max∆EmissionAnnual,∆Emission24hr		(2A-6)
For the Kern County example, a total 794 tons of primary PM2.5 emission reductions are needed to meet the 12/35 standard combination (i.e., max(794,502)).
The PM2.5 DVs associated with meeting a standard combination at the highest monitor in a county are calculated using the required emission reductions as follows:
      DVAnnual,std.combo=DVAnnual,initial-∆Emissionstd.comboxAQratioAnnual	(2A-8)
      DVDaily,std.combo=DVAnnual,initial-∆Emissionstd.comboxAQratioDaily	(2A-9)
In the Kern County example, the adjusted annual DV for the 12/35 case is 12.04 g m[-3] (14.54-794*3.15/1000) and the adjusted 24-hour DV is 32.5 g m[-3] (40.4-794*9.97/1000).
       2A.3.4.1 Emission Reductions Needed to Meet 12/35
In the 2032 projections, PM2.5 DVs exceeded the existing standards for some counties in the west (Figure 2A-26). To create the PM2.5 DVs for 12/35 analytical baseline, the reductions in primary PM2.5 emissions needed to just meet 12/35 at the highest DV monitor by county were calculated using the air quality ratios in Table 2A-9. PM2.5 DVs were then adjusted according to those emission reductions. In Table 2A-13, the primary PM2.5 emission reductions needed to meet 12/35 is shown by county for counties with annual DVs greater than 8 g m[-3] or 24-hour DVs greater than 30 g m[-3] (note that required emission reductions are zero for counties with DVs below 12/35). Table 2A-13 also includes the corresponding air quality ratios, the 2032 PM2.5 DVs (or NOx-adjusted DVs for South Coast and SJV counties), and the PM2.5 DVs that define the 12/35 analytical baseline.
Table 2A-13	Summary of Primary PM2.5 Emissions Reductions by County Needed to Meet the Existing Standards (12/35) for Counties with 2032[a] Annual DVs greater than 8 g m-3 or 24-Hour DVs Greater than 30 g m[-3]
State
County
                                  Emission
                                 2032 to 12/35
                                     (ton)
                                   AQ Ratio
                                    Annual
                              (g m-3 per kton)
                                   AQ Ratio
                                    24-hour
                              (g m-3 per kton)
                                  2032[a] DV
                                    Annual
                                 (g m[-3])
                                  2032[a] DV
                                    24-hour
                                 (g m[-3])
                                   12/35 DV
                                    Annual
                                 (g m[-3])
                                   12/35 DV
                                    24-hour
                                 (g m[-3])
AL
Jefferson
                                       0
                                     1.22
                                     3.51
                                     9.86
                                     20.1
                                     9.86
                                     20.1
AL
Talladega
                                       0
                                     1.22
                                     3.51
                                     8.20
                                     16.3
                                     8.20
                                     16.3
AZ
Maricopa
                                       0
                                     2.14
                                     8.70
                                     9.47
                                     26.7
                                     9.47
                                     26.7
AZ
Pinal
                                       0
                                     2.14
                                     8.70
                                     8.16
                                     34.2
                                     8.16
                                     34.2
AZ
Santa Cruz
                                       0
                                     2.14
                                     8.70
                                     8.99
                                     26.5
                                     8.99
                                     26.5
AR
Pulaski
                                       0
                                     1.22
                                     3.51
                                     8.99
                                     19.3
                                     8.99
                                     19.3
AR
Union
                                       0
                                     1.22
                                     3.51
                                     8.12
                                     17.0
                                     8.12
                                     17.0
CA
Alameda
                                       0
                                     3.15
                                     9.97
                                     10.14
                                     25.4
                                     10.14
                                     25.4
CA
Butte
                                       0
                                     3.15
                                     9.97
                                     8.28
                                     27.2
                                     8.28
                                     27.2
CA
Contra Costa
                                       0
                                     3.15
                                     9.97
                                     9.16
                                     25.1
                                     9.16
                                     25.1
CA
Fresno
                                      189
                                     3.15
                                     9.97
                                     12.03
                                     37.3
                                     11.43
                                     35.4
CA
Imperial
                                      349
                                     1.18
                                     2.56
                                     12.45
                                     32.4
                                     12.04
                                     31.5
CA
Kern
                                      791
                                     3.15
                                     9.97
                                     14.54
                                     40.4
                                     12.04
                                     32.5
CA
Kings
                                      104
                                     3.15
                                     9.97
                                     12.37
                                     29.5
                                     12.04
                                     28.4
CA
Los Angeles
                                      313
                                     1.18
                                     2.56
                                     12.41
                                     31.9
                                     12.04
                                     31.1
CA
Madera
                                       0
                                     3.15
                                     9.97
                                     10.60
                                     31.1
                                     10.60
                                     31.1
CA
Marin
                                       0
                                     3.15
                                     9.97
                                     8.18
                                     23.4
                                     8.18
                                     23.4
CA
Merced
                                       0
                                     3.15
                                     9.97
                                     10.79
                                     29.1
                                     10.79
                                     29.1
CA
Napa
                                       0
                                     3.15
                                     9.97
                                     10.09
                                     25.7
                                     10.09
                                     25.7
CA
Orange
                                       0
                                     1.18
                                     2.56
                                     7.47
                                     28.5
                                     7.47
                                     28.5
CA
Plumas
                                     1,244
                                     3.15
                                     9.97
                                     14.52
                                     47.8
                                     10.60
                                     35.4
CA
Riverside
                                     1,478
                                     1.18
                                     2.56
                                     13.78
                                     36.9
                                     12.04
                                     33.1
CA
Sacramento
                                       0
                                     3.15
                                     9.97
                                     9.29
                                     31.0
                                     9.29
                                     31.0
CA
San Bernardino
                                     2,209
                                     1.18
                                     2.56
                                     14.64
                                     32.0
                                     12.04
                                     26.3
CA
San Diego
                                       0
                                     1.18
                                     2.56
                                     9.16
                                     22.3
                                     9.16
                                     22.3
CA
San Joaquin
                                       0
                                     3.15
                                     9.97
                                     10.08
                                     29.1
                                     10.08
                                     29.1
CA
San Luis Obispo
                                       0
                                     3.15
                                     9.97
                                     9.63
                                     25.1
                                     9.63
                                     25.1
CA
Santa Clara
                                       0
                                     3.15
                                     9.97
                                     9.56
                                     26.0
                                     9.56
                                     26.0
CA
Siskiyou
                                       0
                                     3.15
                                     9.97
                                     7.77
                                     34.8
                                     7.77
                                     34.8
CA
Solano
                                       0
                                     3.15
                                     9.97
                                     9.04
                                     24.7
                                     9.04
                                     24.7
CA
Stanislaus
                                       0
                                     3.15
                                     9.97
                                     11.08
                                     29.8
                                     11.08
                                     29.8
CA
Sutter
                                       0
                                     3.15
                                     9.97
                                     8.82
                                     27.6
                                     8.82
                                     27.6
CA
Tulare
                                      230
                                     3.15
                                     9.97
                                     12.76
                                     27.6
                                     12.04
                                     25.3
CA
Ventura
                                       0
                                     1.18
                                     2.56
                                     9.23
                                     33.5
                                     9.23
                                     33.5
CO
Denver
                                       0
                                     2.14
                                     8.70
                                     9.04
                                     24.1
                                     9.04
                                     24.1
CO
Weld
                                       0
                                     2.14
                                     8.70
                                     8.14
                                     24.9
                                     8.14
                                     24.9
DE
New Castle
                                       0
                                     1.37
                                     4.33
                                     8.14
                                     21.4
                                     8.14
                                     21.4
DC
District of Columbia
                                       0
                                     1.22
                                     3.51
                                     8.21
                                     19.8
                                     8.21
                                     19.8
GA
Bibb
                                       0
                                     1.22
                                     3.51
                                     8.80
                                     18.3
                                     8.80
                                     18.3
GA
Clayton
                                       0
                                     1.22
                                     3.51
                                     8.57
                                     17.2
                                     8.57
                                     17.2
GA
Cobb
                                       0
                                     1.22
                                     3.51
                                     8.09
                                     16.6
                                     8.09
                                     16.6
GA
DeKalb
                                       0
                                     1.22
                                     3.51
                                     8.08
                                     18.2
                                     8.08
                                     18.2
GA
Dougherty
                                       0
                                     1.22
                                     3.51
                                     8.38
                                     21.3
                                     8.38
                                     21.3
GA
Floyd
                                       0
                                     1.22
                                     3.51
                                     8.72
                                     17.3
                                     8.72
                                     17.3
GA
Fulton
                                       0
                                     1.22
                                     3.51
                                     9.46
                                     20.4
                                     9.46
                                     20.4
GA
Gwinnett
                                       0
                                     1.22
                                     3.51
                                     8.06
                                     18.7
                                     8.06
                                     18.7
GA
Muscogee
                                       0
                                     1.22
                                     3.51
                                     8.68
                                     27.3
                                     8.68
                                     27.3
GA
Richmond
                                       0
                                     1.22
                                     3.51
                                     8.54
                                     21.0
                                     8.54
                                     21.0
GA
Wilkinson
                                       0
                                     1.22
                                     3.51
                                     8.97
                                     19.2
                                     8.97
                                     19.2
ID
Benewah
                                       0
                                     2.14
                                     8.70
                                     9.61
                                     35.2
                                     9.61
                                     35.2
ID
Canyon
                                       0
                                     2.14
                                     8.70
                                     8.86
                                     31.4
                                     8.86
                                     31.4
ID
Lemhi
                                      460
                                     2.14
                                     8.70
                                     11.03
                                     39.4
                                     10.05
                                     35.4
ID
Shoshone
                                      138
                                     2.14
                                     8.70
                                     11.04
                                     36.6
                                     10.75
                                     35.4
IL
Cook
                                       0
                                     1.37
                                     4.33
                                     9.43
                                     20.7
                                     9.43
                                     20.7
IL
Madison
                                       0
                                     1.37
                                     4.33
                                     9.03
                                     19.0
                                     9.03
                                     19.0
IL
Saint Clair
                                       0
                                     1.37
                                     4.33
                                     8.99
                                     17.6
                                     8.99
                                     17.6
IN
Allen
                                       0
                                     1.37
                                     4.33
                                     8.10
                                     19.6
                                     8.10
                                     19.6
IN
Clark
                                       0
                                     1.37
                                     4.33
                                     8.58
                                     19.8
                                     8.58
                                     19.8
IN
Elkhart
                                       0
                                     1.37
                                     4.33
                                     8.37
                                     23.5
                                     8.37
                                     23.5
IN
Floyd
                                       0
                                     1.37
                                     4.33
                                     8.08
                                     18.0
                                     8.08
                                     18.0
IN
Lake
                                       0
                                     1.37
                                     4.33
                                     8.92
                                     22.2
                                     8.92
                                     22.2
IN
Marion
                                       0
                                     1.37
                                     4.33
                                     9.61
                                     22.0
                                     9.61
                                     22.0
IN
St. Joseph
                                       0
                                     1.37
                                     4.33
                                     8.72
                                     20.4
                                     8.72
                                     20.4
IN
Vanderburgh
                                       0
                                     1.37
                                     4.33
                                     8.40
                                     17.5
                                     8.40