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EXECUTIVE SUMMARY

Overview

In setting primary national ambient air quality standards (NAAQS), the EPA’s 

responsibility under the law is to establish standards that protect public health. The Clean Air Act 

(the Act) requires the EPA, for each criteria pollutant, to set a standard that protects public health 

with “an adequate margin of safety.” As interpreted by the Agency and the courts, the Act 

requires the EPA to base this decision on health considerations only; economic factors cannot be 

considered. The prohibition against considering cost in the setting of the primary air quality 

standards does not mean that costs, benefits or other economic considerations are unimportant. 

The Agency believes that consideration of costs and benefits is an essential decision-making tool 

for the efficient implementation of these standards. The impacts of costs, benefits, and efficiency 

are considered by the States when they make decisions regarding what timelines, strategies, and 

policies are appropriate for their circumstances.

The EPA is proposing to revise the level of the ozone NAAQS to within a range of 65

ppb to 70 ppb and is soliciting comment on alternative standard levels below 65 ppb, as low as 

60 ppb. The EPA is also proposing to revise the level of the secondary standard to within the 

range proposed for the primary standard of 65 ppb to 70 ppb to provide increased protection 

against vegetation-related effects on public welfare.1 The EPA performed an illustrative analysis 

of the potential costs, human health benefits, and welfare co-benefits of nationally attaining 

primary alternative ozone standard levels and did not estimate any incremental costs and benefits 

associated with attaining a revised secondary standard. Per Executive Order 12866 and the 

guidelines of OMB Circular A-4, this Regulatory Impact Analysis (RIA) presents the analyses of 

the following alternative standard levels -- 70 ppb, 65 ppb, and 60 ppb. The cost and benefit 

estimates below are calculated incremental to a 2025 baseline that incorporates air quality 

improvements achieved through the projected implementation of existing regulations and full 

attainment of the existing ozone NAAQS (75 ppb). The 2025 baseline reflects, among other 

 

1 As an initial matter, the EPA is proposing that ambient ozone concentrations in terms of a three-year average 

W126 index value within the range from 13 parts per million-hours (ppm-hours) to 17 ppm-hours would provide the 

requisite protection against known or anticipated adverse effects to the public welfare, which data analyses indicate 

would provide air quality in terms of three-year average W126 index values of a range at or below 13 ppm-hours to 

17 ppm-hours. Data analyses also indicate that actions taken to attain a standard in the range of 65 ppb to 70 ppb 

would also improve air quality as measured by the W126 metric.
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existing regulations, the Mercury and Air Toxics Standard, the Clean Air Interstate Rule, the Tier 

3 Motor Vehicle Emission and Fuel Standards, and adjustments for the Clean Power Plan, all of 

which will help many areas move toward attainment of the existing ozone standard (see Chapter 

3, Section 3.1.3 for additional information). 

In this RIA we present the primary costs and benefits estimates for 2025. We assume 

that potential nonattainment areas everywhere in the U.S., excluding California, will be 

designated such that they are required to reach attainment by 2025, and we developed our 

projected baselines for emissions, air quality, and populations for 2025. 

The EPA will likely finalize designations for a revised ozone NAAQS in late 

2017. Depending on the precise timing of the effective date of those designations, nonattainment 

areas classified as Marginal will likely have to attain in either late 2020 or early 

2021. Nonattainment areas classified as Moderate will likely have to attain in either late 2023 or 

early 2024. If a Moderate nonattainment area qualifies for two 1-year extensions, the area may 

have as late as 2026 to attain. Lastly, Serious nonattainment areas will likely have to attain in 

late 2026 or early 2027. We selected 2025 as the primary year of analysis because most areas of 

the U.S. will likely be required to meet a revised ozone standard by 2025 and because it provided 

a good representation of the remaining air quality concerns that Moderate nonattainment areas 

would face; states with areas classified as Moderate and higher are required to develop 

attainment demonstration plans for those nonattainment areas.

In estimating the incremental costs and benefits of potential alternative standards, we 

recognize that there are several areas that are not required to meet the existing ozone standard by 

2025. The Clean Air Act allows areas with more significant air quality problems to take 

additional time to reach the existing standard. Several areas in California are not required to 

meet the existing standard by 2025 and may not be required to meet a revised standard until

sometime between 2032 and 2038.2 We were not able to project emissions and air quality 

beyond 2025 for California, however, we adjusted baseline air quality to reflect mobile source 

 

2 The EPA will likely finalize designations for a revised ozone NAAQS in late 2017. Depending on the precise 

timing of the effective date of those designations, nonattainment areas classified as Severe 15 will likely have to 

attain sometime between late 2032 and early 2033 and nonattainment areas classified as Extreme will likely have to 

attain sometime between late 2037 and early 2038. 
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emissions reductions for California that would occur between 2025 and 2030; these emissions 

reductions were the result of mobile source regulations expected to be fully implemented by 

2030. While there is uncertainty about the precise timing of emissions reductions and related 

costs for California, we assume costs occur through 2038. In addition, we model benefits for 

California using projected population demographics for 2038. 

Because of the different timing for incurring costs and accruing benefits and for ease of 

discussion throughout the analyses, we refer to the different time periods for potential attainment 

as 2025 and post-2025 to reflect that (1) we did not project emissions and air quality for any year 

other than 2025; (2) for California, emissions controls and associated costs are assumed to occur 

through 2038; and (3) for California benefits are modeled using population demographics in 

2038. It is not straightforward to discount the post-2025 results for California to compare with 

or add to the 2025 results for the rest of the U.S. While we estimate benefits using 2038 

information, we do not have good information on precisely when the costs of controls will be 

incurred. Because of these differences in timing related to California attaining a revised 

standard, the supplementalseparate costs and benefits estimates for post-2025 should not be 

added to the primary estimates for 2025.

ES.1 Overview of Analytical Approach

This RIA consists of multiple analyses including an assessment of the nature and sources 

of ambient ozone (Chapter 2 – Defining the Air Quality Problem); estimates of current and 

future emissions of relevant precursors that contribute to the problem; air quality analyses of 

baseline and alternative control strategies (Chapter 3 – Air Quality Modeling and Analysis); 

development of illustrative control strategies to attain the primary alternative standard levels 

(Chapter 4 – Control Strategies and Emissions Reductions); estimates of the incremental benefits 

of attaining the primary alternative standard levels (Chapter 5 – Human Health Benefits); a 

qualitative discussion of the welfare co-benefits of attaining the primary alternative standard 

levels (Chapter 6 – Welfare Co-Benefits of the Primary Standard); estimates of the incremental 

costs of attaining the primary alternative standard levels (Chapter 7 – Engineering Cost Analysis 

and Economic Impacts); a comparison and discussion of the benefits and costs (Chapter 8 –

Comparison of Costs and Benefits); an analysis of the impacts of the relevant statutory and 

executive orders (Chapter 9 – Statutory and Executive Order Impact Analysis); and a discussion 
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of the theoretical framework used to analyze regulation-induced employment impacts, as well as 

information on employment related to installation of NOx controls on coal and gas-fired electric 

generating units, industrial boilers, and cement kilns (Chapter 10 – Qualitative Discussion of 

Employment Impacts of Air Quality).

Because States are ultimately responsible for implementing strategies to meet revised 

standards, this RIA provides insights and analysis of a limited number of illustrative control 

strategies that states might adopt to meet a revised standard. The goal of this RIA is to provide 

estimates of the costs and benefits of the illustrative attainment strategies to the meet each

alternative standard level. The flowchart below (Figure ES-1) outlines the analytical steps taken 

to illustrate attainment with the potential alternative standard levels, and the following 

discussion, by primary flowchart section, describes the steps taken. 

Figure ES-1. Analytical Flowchart for Primary Standards Analyses
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ES.1.1 Establishing the Baseline

The future year base case reflects emissions projected from 2011 to 2025 and 

incorporates current state and federal programs, including the Tier 3 Motor Vehicle Emission 

and Fuel Standards (U.S. EPA, 2014a) (see Chapter 3, Section 3.1.3 for a discussion of the rules 

included in the base case). The base case does not include control programs specifically for the 

purpose of attaining the existing ozone standard (75 ppb). The baseline builds on the future year 

base case and reflects the additional emissions reductions needed to reach attainment of the 

current ozone standard (75 ppb), as well as adjustments for the Clean Power Plan (U.S. EPA, 

2014b).

We performed a national scale air quality modeling analysis to estimate ozone 

concentrations for the future base case year of 2025. To accomplish this, we modeled multiple 

emissions cases for 2025, including the 2025 base case and twelve 2025 emissions sensitivity 

simulations. The twelve emissions sensitivity simulations were used to develop ozone sensitivity 

factors (ppb/ton) from the modeled response of ozone to changes in NOx and VOC emissions 

from various sources and locations. These ozone sensitivity factors were then used to determine 

the amount of emissions reductions needed to reach the 2025 baseline and evaluate potential 

alternative standard levels of 70, 65, and 60 ppb incremental to the baseline. We used the 

estimated emissions reductions needed to reach each of these standard levels to analyze the costs 

and benefits of alternative standard levels. 

ES.1.2 Control Strategies and Emissions Reductions

The EPA analyzed illustrative control strategies that areas across the U.S. might employ 

to attain alternative revised primary ozone standard levels of 70, 65, and 60 ppb. The EPA 

analyzed the impact that additional emissions control technologies and measures, across 

numerous sectors, would have on predicted ambient ozone concentrations incremental to the 

baseline. These control measures, also referred to as known controls, are based on information 

available at the time of this analysis and include primarily end-of-pipe control technologies. In 

addition, to attain some of the alternative primary standard levels analyzed, some areas needed 

additional emissions reductions beyond the known controls, and we refer to these as unknown 

controls (see Chapter 7, Section 7.2 for additional information).
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Using average ozone response factors, we estimated the portion of the emissions 

reductions required to meet the baseline, including any additional emissions reductions beyond 

known controls. We then estimated the emissions reductions incremental to the baseline that 

were needed to meet the alternative standard levels of 70, 65, and 60 ppb. Costs of controls 

incremental to (i.e., over and above) the baseline emissions reductions are attributed to the costs 

of meeting the alternative standard levels. These emissions reductions can come from both 

specific known controls, as well as unknown controls. The baseline shows that by 2025, while 

ozone air quality would be significantly better than today under current requirements, depending 

on the alternative standard level analyzed, several areas in the Eastern, Central, and Western U.S. 

would need to develop and adopt additional controls to attain alternative standard levels (see 

Chapter 4, Section 4.3). 

ES.1.2.1 Emissions Reductions from Known Controls in 2025

Figure ES-2 shows the counties projected to exceed the alternative standard levels 

analyzed for 2025 for areas other than California. For the 70 ppb alternative standard level, 

emissions reductions were required for monitors in the Central and Northeast regions. For the 65 

and 60 ppb alternative standard levels, emissions reductions were applied in all regions with 

projected baseline design values (DVs) above these levels.3 For the 60 ppb alternative standard 

level, additional VOC emissions reductions were identified in Chicago because some sites in that 

area experienced NOx disbenefits, meaning that the regional NOx emissions reductions resulted 

in ozone increases from below 60 ppb to above 60 ppb. Tables ES-1 through ES-3 show the 

emissions reductions from known controls for the alternative standard levels analyzed. 

 

3 A design value is a statistic that describes the air quality status of a given area relative to the level of the NAAQS. 

Design values are typically used to classify nonattainment areas, assess progress toward meeting the NAAQS, and 

develop control strategies.
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Figure ES-2. Projected Ozone Design Values in the 2025 Baseline Scenario
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Table ES-1. Summary of Emission Reductions by Sector for Known Controls for 70 ppb 

Proposed Alternative Standard Level for 2025, except California (1,000 

tons/year)a

Geographic Area Emissions Sector NOx VOC

East

EGU 25 -

Non-EGU Point 210 0.98

Nonpoint 260 54

Nonroad 5 -

Total 490 55

West

EGU - -

Non-EGU Point - -

Nonpoint - -

Nonroad - -

Total - -

a Estimates are rounded to two significant figures. 

Table ES-2. Summary of Emission Reductions by Sector for Known Controls for 65 ppb 

Proposed Alternative Standard Level for 2025 - except California (1,000 

tons/year)a

Geographic Area Emissions Sector NOx VOC

East

EGU 170 -

Non-EGU Point 410 3.6

Nonpoint 420 95

Nonroad 12 -

Total 1,000 99

West

EGU 36 -

Non-EGU Point 38 0.47

Nonpoint 37 6.6

Nonroad 1.3 -

Total 110 7

a Estimates are rounded to two significant figures.

Table ES-3. Summary of Emission Reductions by Sector for Known Controls for 60 ppb 

Alternative Standard Level for 2025 - except California (1,000 tons/year)a

Geographic Area Emissions Sector NOx VOC

East

EGU 170 -

Non-EGU Point 410 4.2

Nonpoint 420 99

Nonroad 12 -

Total 1,000 100

West

EGU 62 -

Non-EGU Point 48 0.47

Nonpoint 39 6.6

Nonroad 1.3 -

Total 150 7

a Estimates are rounded to two significant figures. 
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ES.1.2.2 Emissions Reductions beyond Known Controls in 2025

There were several areas where known controls did not achieve enough emissions 

reductions to attain the proposed alternative standard levels of 70 and 65 as well as the more 

stringent alternative standard level of 60 ppb. To complete the analysis, the EPA then estimated 

the additional emissions reductions beyond known controls needed to reach attainment (i.e., 

unknown controls). Table ES-4 shows the emissions reductions needed from unknown controls 

in 2025 for the U.S., except California, for the alternative standard levels analyzed.

Table ES-4. Summary of Emissions Reductions by Alternative Standard for Unknown 

Controls for 2025 - except California (1,000 tons/year)a

Region NOx VOC

Proposed Alternative Standard Levels

70 ppb East

West

150

-

-

-

65 ppb East

West

750

-

-

-

Alternative Standard Level

60 ppb East

West

1,900

350

41

-

ES.1.2.3 Emissions Reductions beyond Known Controls for Post-2025

Figure ES-3 shows the counties projected to exceed the alternative standard levels 

analyzed for the post-2025 analysis for California. For the California post-2025 alternative 

standard level analyses, all known controls were applied in the baseline, so incremental 

emissions reductions are from unknown controls. Table ES-5 shows the emissions reductions 

needed from unknown controls for post-2025 for California for the alternative standard levels 

analyzed.
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Figure ES-3. Projected Ozone Design Values in the post-2025 Baseline Scenario

Table ES-5. Summary of Emissions Reductions by Alternative Standard Level for 

Unknown Controls for post-2025 - California (1,000 tons/year)a

Region NOx VOC

Proposed Alternative Standard Levels

70 ppb CA 53 -

65 ppb CA 110 -

Alternative Standard Level

60 ppb CA 140 -

a Estimates are rounded to two significant figures. 

ES.1.3 Human Health Benefits

To estimate benefits, we follow a “damage-function” approach in calculating total 

benefits of the modeled changes in environmental quality. This approach estimates changes in 

individual health endpoints (specific effects that can be associated with changes in air quality) 

and assigns values to those changes assuming independence of the values for those individual 

endpoints. Total benefits are calculated as the sum of the values for all non-overlapping health 

endpoints. The “damage-function” approach is the standard method for assessing costs and 

benefits of environmental quality programs and has been used in several recent published 

analyses (Levy et al., 2009; Fann et al., 2012a; Tagaris et al., 2009).
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To assess economic values in a damage-function framework, the changes in 

environmental quality must be translated into effects on people or on the things that people 

value. In some cases, the changes in environmental quality can be directly valued, as is the case 

for changes in visibility. In other cases, such as for changes in ozone and PM, an impact analysis 

must first be conducted to convert air quality changes into effects that can be assigned dollar 

values. For the purposes of this RIA, the health impacts analysis is limited to those health effects 

that are directly linked to ambient levels of air pollution and specifically to those linked to ozone 

and PM2.5.

Benefits estimates for ozone were generated using the damage function approach outlined 

above wherein potential changes in ambient ozone levels (associated with future attainment of 

alternative standard levels) were explicitly modeled and then translated into reductions in the 

incidence of specific health endpoints. In generating ozone benefits estimates for the two 

attainment timeframes considered in the RIA (2025 and post-2025), we used three distinct 

benefits simulations including one completed for 2025 and two completed for 2038. The way in 

which these three benefits simulations were used to generate estimates for the two timeframes is 

detailed in Chapter 5, Section 5.4.3. 

In contrast to ozone, we used a benefit-per-ton approach in modeling PM2.5 co-benefits. 

With this approach, we use the results of previous benefits analysis simulations focusing on 

PM2.5 to derive benefits-per-ton estimates for NOx.4 We then combine these dollar-per-ton 

estimates with projected reductions in NOx associated with meeting a given alternative standard 

level to project cobenefits associated with PM2.5. We acknowledge increased uncertainty 

associated with the dollar-per-ton approach for PM2.5,relative to explicitly modeling benefits 

using gridded PM2.5 surfaces specific to the baseline and alternative standard levels (see 

Appendix 5A, Table 5A-1 for additional discussion). 

In addition to ozone and PM2.5 benefits, implementing emissions controls to reach some of 

the alternative ozone standard levels would reduce other ambient pollutants. However, because 

the methods used in this analysis to simulate attainment do not account for changes in ambient 

 

4

In addition to dollar-per-ton estimates for NOx, we also used incidence-per-ton values (also for NOx) for specific 

health endpoints to generate incidence reduction estimates associated with the dollar benefits. 
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concentrations of other pollutants, we were not able to quantify the co-benefits of reduced 

exposure to these pollutants. In addition, due to data and methodology limitations, we were 

unable to estimate some anticipated health benefits associated with exposure to ozone and PM2.5.

ES.1.4 Welfare Co-Benefits of the Primary Standard

Section 109 of the Clean Air Act defines welfare effects to include any non-health effects, 

including direct economic damages in the form of lost productivity of crops and trees, indirect 

damages through alteration of ecosystem functions, indirect economic damages through the loss 

in value of recreational experiences or the existence value of important resources, and direct 

damages to property, either through impacts on material structures or by soiling of surfaces (42 

U.S.C. 7409). Ozone can affect ecological systems, leading to changes in the ecological 

community and influencing the diversity, health, and vigor of individual species (U.S. EPA, 

2013). Ozone causes discernible injury to a wide array of vegetation (U.S. EPA, 2013). In terms 

of forest productivity and ecosystem diversity, ozone may be the pollutant with the greatest 

potential for region-scale forest impacts (U.S. EPA, 2013). Studies have demonstrated repeatedly 

that ozone concentrations observed in polluted areas can have substantial impacts on plant 

function (De Steiguer et al,. 1990; Pye, 1988).

In this RIA, we are able to quantify only a small portion of the welfare impacts associated 

with reductions in ozone concentrations to meet alternative ozone standards. Using a model of 

commercial agriculture and forest markets, we are able to analyze the effects on consumers and 

producers of forest and agricultural products of changes in the W126 index resulting from 

meeting alternative standards within the proposed range of 70 to 65 ppb, as well as a lower 

standard level of 60 ppb. We also assess the effects of those changes in commercial agricultural 

and forest yields on carbon sequestration and storage. This analysis provides limited quantitative 

information on the welfare co-benefits of meeting these alternative standards, focused only on 

one subset of ecosystem services. Commercial and non-commercial forests provide a number of 

additional services, including medicinal uses, non-commercial food and fiber production, arts 

and crafts uses, habitat, recreational uses, and cultural uses for Native American tribes. A more 

complete discussion of these additional ecosystem services is provided in the final Welfare Risk 

and Exposure Assessment for Ozone (U.S. EPA, 2014c).
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ES.2 Results of Benefit-Cost Analysis

Below in Table ES-6, we present the primary costs and benefits estimates for 2025 for all 

areas except California. In addition, Tables 5-1 and 5-23 in Chapter 5 provide a breakdown of 

ozone-only and PM2.5-only benefits, as well as total benefits at 3 percent. We anticipate that 

benefits and costs will likely begin occurring earlier, as states begin implementing control 

measures to show progress towards attainment. In these tables, ranges within the total benefits 

rows reflect variability in the studies upon which the estimates associated with premature 

mortality were derived. PM2.5 co-benefits account for approximately two-thirds to three-quarters 

of the estimated benefits, depending on the standard analyzed and on the choice of ozone and 

PM mortality functions used. In addition for 2025, Table ES-7 presents the numbers of 

premature deaths avoided for the alternative standard levels analyzed, as well as the other health 

effects avoided. Table ES-8 provides information on the costs by geographic region for the U.S., 

except California in 2025, and Table ES-9 provides a regional breakdown of benefits for 2025.

In the RIA we provide estimates of costs of emissions reductions to attain the proposed 

standards in three regions -- California, the rest of the western U.S., and the eastern U.S. In 

addition, we provide estimates of the benefits that accrue to each of these three regions resulting 

from (i) control strategies applied within the region, (ii) reductions in transport of ozone 

associated with emissions reductions in other regions, and (iii) the control strategies for which 

the regional cost estimates are generated. These benefits are not directly comparable to the costs 

of control strategies in a region because the benefits include benefits not associated with those 

control strategies.

The net benefits of emissions reductions strategies in a specific region would be the 

benefits of the emissions reductions occurring both within and outside of the region minus the 

costs of the emissions reductions. Because the air quality modeling is done the national level, we 

do not estimate separately the nationwide benefits associated with the emissions reductions 

occurring in any specific region.5 As a result, we are only able to provide net benefits estimates 

at the national level. The difference between the costs for a specific region and the benefits 

 

5 For California, we provide separate estimates of the costs and nationwide estimates of benefits, so it is appropriate 

to calculate net benefits. As such, we provide net benefits for the post-2025 California analysis.
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accruing to that region is not an estimate of net benefits of the emissions reductions in that 

region.

Table ES-6. Total Annual Costs a and Benefits bafor U.S., except California in 2025 

(billions of 2011$, 7% Discount Rate)b

Proposed Alternative Standard Levels Alternative Standard 

Level

70 ppb 65 ppb 60 ppb

Total Costs (7%) $3.9 $15 $39

Health Benefits (3%)c $6.9 to $14.0 $20 to $41 $37 to $75

Total Health Benefits (7%)c $6.4 to $13.0 $19 to $38 $34 to $70

Net Benefits (3%) $3.0 to $10.1 $5 to $26 ($2) to $36

Net Benefits (7%) $2.5 to $9.1 $4 to $23 ($5) to $31

a Engineering costs reflect 7% discount rate. We do not have a comprehensive data set to be able to calculate 

engineering costs at a 3% discount rate.

ba Benefits are nationwide benefits of attainment everywhere except California.

b EPA believes that providing comparisons of social costs and social benefits at 3 and 7 percent is appropriate. 

Estimating multiple years of costs and benefits is not possible for this RIA due to data and resource limitations. As 

a result, we provide a snapshot of costs and benefits in 2025, using the best available information to approximate 

social costs and social benefits recognizing uncertainties and limitations in those estimates.

cc The benefits range reflects the LOW and UPPER core estimates of short-term ozone and long-term PM mortality.

EPA believes that providing comparisons of social costs and social benefits at 3 and 7 

percent is appropriate. Ideally, streams of social costs and social benefits over time would be 

estimated and the net present values of each would be compared to determine net benefits of the 

illustrative attainment strategies. The three different uses of discounting in the RIA – (i) 

construction of annualized engineering costs, (ii) adjusting the value of mortality risk for lags in 

mortality risk decreases, and (iii) adjusting the cost of illness for non-fatal heart attacks to adjust 

for lags in follow up costs -- are all appropriate. Our estimates of net benefits are the 

approximations of the net value (in 2025) of benefits attributable to emissions reductions needed 

to attain just for the year 2025.

Table ES-7. Summary of Total Number of Annual Ozone and PM-Related Premature 

Mortalities and Premature Morbidity: 2025 National Benefits a 

Proposed Alternative Standard Levels

(95th percentile confidence intervals)b

Alternative Standard 

Level

(95th percentile 

confidence intervals)

70 ppb 65 ppb 60 ppb

Short-term exposure-related 

premature deaths avoided (all ages) 

(Ozone – 2 studies)

200 to 340

(97 to 300)

(180 to 490)

630 to 1,000

(310 to 940)

(560 to 1,500)

1,100 to 1,900

(560 to 1,700)

(1,000 to 2,800)

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Proposed Alternative Standard Levels

(95th percentile confidence intervals)b

Alternative Standard 

Level

(95th percentile 

confidence intervals)

70 ppb 65 ppb 60 ppb

Long-term exposure-related 

premature deaths avoided (age 

30+) (PM – 2 studies)

O3: 680

(230 to 1,100)

PM2.5: 510 to 1,100c

O3: 2,100

(710 to 3,500)

PM2.5: 1,400 to 3,300c

O3: 3,900

(1,300 to 6,400)

PM2.5: 2,600 to 6,000c

Other health effects avoidedd

Non-fatal heart attacks (age 18-99) (5 

studies) PM 64 to 600 180 to 1,700 330 to 3,100

Respiratory hospital admissions (age 

0-99)O3, PM 510 1,600 2,900

Cardiovascular hospital admissions 

(age 18-99) PM 180 530 950

Asthma emergency department visits 

(age 0-18) O3, PM 1,400 4,300 8,000

Acute bronchitis (age 8-12) PM 790 2,300 4,100

Asthma exacerbation (age 6-18) O3, PM 320,000 970,000 1,800,000

Lost work days (age 18-65) PM 65,000 180,000 340,000

Minor restricted activity days (age 

18-65) O3, PM 1,300,000 3,900,000 7,300,000

Upper & lower respiratory symptoms 

(children) PM 25,000 70,000 130,000

School loss days O3 330,000 1,000,000 1,900,000

a Nationwide benefits of attainment everywhere except California. 

b We present a confidence interval in parentheses for each study on short-term or long-term ozone-related mortality.

c These estimates were generated using benefit-per-ton estimates and confidence intervals are not available. In 

general, the 95th percentile confidence interval for the health impact function alone ranges from + 30 percent for 

mortality incidence based on Krewski et al. (2009) and + 46 percent based on Lepeule et al. (2012).

d See Table 5-19 in Chapter 5 for detailed information on confidence intervals related to ozone-related morbidity 

incidence estimates. The PM2.5 morbidity incidence estimates were generated using benefit-per-ton estimates and 

confidence intervals are not available.

Table ES-8. Summary of Total Control Costs (Known and Extrapolated) by Alternative 

Level for 2025 - U.S., except California (billions of 2011$, 7% Discount Rate)a

Alternative Level Geographic Area Total Control Costs (Known and 

Extrapolated)

70 ppb

East 3.9

West -

Total $3.9

65 ppb

East 15

West 0.40

Total $15

60 ppb

East 33

West 5.8

Total $39

a All values are rounded to two significant figures. Extrapolated costs are based on the average-cost methodology.

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Table ES-9. Regional Breakdown of Monetized Ozone-Specific Benefits Results for the 

2025 Scenario (nationwide benefits of attaining each alternative standard 

everywhere in the U.S. except California) – Full Attainment a

Region

Proposed and Alterative Standards

70 ppb 65 ppb 60 ppb

East b 99% 96% 92%

California 0% 0% 0%

Rest of West 1% 4% 7%

a Because we use benefit-per-ton estimates to calculate the PM2.5 co-benefits, a regional breakdown for the cobenefits is not available. Therefore, this table only reflects the ozone benefits.

b

Includes Texas and those states to the north and east. Several recent rules such as Tier 3 will have substantially 

reduced ozone concentrations by 2025 in the East, thus few additional controls would be needed to reach 70 ppb. 

To understand possible additional costs and benefits of fully attaining in California in a 

post-2025 timeframe, we provide supplementalseparate results for California in Table ES-810. 

In addition, Tables 5-2 and 5-30 in Chapter 5 provide a breakdown of ozone-only and PM2.5-only 

benefits, as well as total benefits at 3 percent. Relative to the primary cost and benefits 

estimates, the California cost estimates are between 5 and 20 percent and the benefits estimates 

are between 8 and 15 percent of the national estimates. Because of the differences in the timing 

of achieving needed emissions reductions, incurring costs, and accruing benefits for California, 

the supplementalseparate costs and benefits estimates for post-2025 should not be added to the 

primary estimates for 2025. For the post-2025 timeframe, Table ES-911 presents the numbers of 

premature deaths avoided for the alternative standard levels analyzed, as well as the other health 

effects avoided. Table ES-12 provides information on the costs for California for post-2025, and 

Table ES-13 provides a regional breakdown of benefits for post-2025.

The EPA presents separate and supplemental costs and benefits results for California 

because forcing attainment in an earlier year than would be required under the Clean Air Act 

would likely lead to an overstatement of costs because California might benefit from some 

existing federal or state programs that would be implemented between 2025 and the ultimate 

attainment years; because additional new technologies may become available between 2025 and 

the attainment years; and because the cost of existing technologies might fall over time. As such, 

we use the best available data to estimate costs and benefits for California in a post-2025 

timeframe, but because of data limitations and additional uncertainty associated with not 

projecting emissions and air quality beyond 2025, we recognize that the estimates of costs and 

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ES-17

benefits for California in a post-2025 timeframe are likely to be relatively more uncertain than 

the national attainment estimates for 2025. 

Table ES-810. Total Annual Costs a and Benefitsba of Control Strategies Applied in 

for California, post-2025 (billions of 2011$, 7% Discount Rate)b

Proposed Alternative Standard Levels Alternative Standard 

Level

70 ppb 65 ppb 60 ppb

Total Costs (7%) $0.80 $1.6 $2.2

Total Health Benefits (7%)c $1.1 to $2 $2.2 to $4.1 $3.2 to $5.9

Net Benefits (7%) $0.3 to $1.2 $0.60 to $2.5 $1 to $3.7

Proposed Alternative Standard Levels Alternative Standard 

Level

70 ppb 65 ppb 60 ppb

Total Costs (7%) $0.80 $1.6 $2.2

Health Benefits (3%)c $1.1 to $2 $2.3 to $4.2 $3.4 to $6.2

Health Benefits (7%)c $1.1 to $2 $2.2 to $4.1 $3.2 to $5.9

Net Benefits (3%) $0.3 to $1.2 $0.70 to $2.6 $1.2 to $4

Net Benefits (7%) $0.3 to $1.2 $0.60 to $2.5 $1 to $3.7

a Engineering costs reflect 7% discount rate. We do not have a comprehensive data set to be able to calculate 

engineering costs at a 3% discount rate.

ba Benefits are nationwide benefits of attainment in California.

b EPA believes that providing comparisons of social costs and social benefits at 3 and 7 percent is appropriate. 

Estimating multiple years of costs and benefits is not possible for this RIA due to data and resource limitations. As 

a result, we provide a snapshot of costs and benefits in 2025, using the best available information to approximate 

social costs and social benefits recognizing uncertainties and limitations in those estimates.

cc The benefits range reflects the LOW and UPPER core estimates of short-term ozone and long-term PM mortality.

Table ES-119. Summary of Total Number of Annual Ozone and PM-Related 

Premature Mortalities and Premature Morbidity: Post-2025a 

Proposed Alternative Standard Levels

(95th percentile confidence intervals)b

Alternative Standard 

Level

(95th percentile 

confidence intervals)

70 ppb 65 ppb 60 ppb

Short-term exposure-related 

premature deaths avoided (all ages) 

(Ozone – 2 studies)

65 to 110

(31 to 97)

(57 to 160)

140 to 230

(68 to 210)

(120 to 340)

210 to 350

(100 to 320)

(190 to 510)

Long-term exposure-related 

premature deaths avoided (age 

30+) (PM – 2 studies)

O3: 260

(88 to 430)

PM2.5: 45 to 100c

O3: 560

(190 to 930)

PM2.5: 89 to 200c

O3: 840

(290 to 1,400)

PM2.5: 120 to 280c

Other health effects avoidedd

Non-fatal heart attacks (age 18-99) (5 

studies) PM 6 to 54 11 to 110 16 to 140

Respiratory hospital admissions (age 

0-99)O3, PM 130 280 430

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ES-18

Proposed Alternative Standard Levels

(95th percentile confidence intervals)b

Alternative Standard 

Level

(95th percentile 

confidence intervals)

70 ppb 65 ppb 60 ppb

Cardiovascular hospital admissions 

(age 18-99) PM 16 32 45

Asthma emergency department visits 

(age 0-18) O3, PM 340 730 1,100

Acute bronchitis (age 8-12) PM 67 130 180

Asthma exacerbation (age 6-18) O3, PM 99,000 210,000 320,000

Lost work days (age 18-65) PM 5,500 11,000 15,000

Minor restricted activity days (age 

18-65) O3, PM 320,000 690,000 1,000,000

Upper & lower respiratory symptoms 

(children) PM 2,100 4,100 5,600

School loss days O3 110,000 230,000 350,000

a Nationwide benefits of attainment in California. 

b We present a confidence interval in parentheses for each study on short-term or long-term ozone-related mortality.

c These estimates were generated using benefit-per-ton estimates and confidence intervals are not available. In 

general, the 95th percentile confidence interval for the health impact function alone ranges from + 30 percent for 

mortality incidence based on Krewski et al. (2009) and + 46 percent based on Lepeule et al. (2012).

d See Table 5-26 in Chapter 5 for detailed information on confidence intervals related to ozone-related morbidity 

incidence estimates. The PM2.5 morbidity incidence estimates were generated using benefit-per-ton estimates and 

confidence intervals are not available.

Table ES-12. Summary of Total Control Costs (Known and Extrapolated) by Alternative 

Level for post-2025 - California (billions of 2011$, 7% Discount Rate)a

Alternative Level Geographic Area

Total Control Costs 

(Known and 

Extrapolated)

70 ppb California $0.80

65 ppb California $1.6

60 ppb California $2.2

a All values are rounded to two significant figures. Extrapolated costs are based on the average-cost methodology.

Table ES-13. Regional Breakdown of Monetized Ozone-Specific Benefits Results for the 

post-2025 Scenario (nationwide benefits of attaining each alternative standard 

just in California) – Full Attainment a

Region

Proposed and Alterative Standards

70 ppb 65 ppb 60 ppb

East 0% 0% 0%

California 93% 94% 94%

Rest of West 6% 6% 6%

a Because we use benefit-per-ton estimates to calculate the PM2.5 co-benefits, a regional breakdown for the cobenefits is not available. Therefore, this table only reflects the ozone benefits.

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ES-19

Despite uncertainties inherent in any complex, quantitative analysis, the overall underlying 

analytical methods used in this RIA have been peer-reviewed. For a detailed discussion on 

uncertainty associated with developing illustrative control strategies to attain the alternative 

standard levels, see Chapter 4, Section 4.4. For a description of the key assumptions and 

uncertainties related to the modeling of ozone benefits, see Chapter 5, Section 5.7.3, and for an 

additional qualitative discussion of sources of uncertainty associated with both the modeling of 

ozone-related benefits and PM2.5-related co-benefits, see Appendix 5A. For a discussion of the 

limitations and uncertainties in the engineering cost analyses, see Chapter 7, Section 7.7. For a 

discussion about generally framing uncertainty, see Chapter 8, Section 8.3. 

ES.3 References

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Fann N, Lamson A, Wesson K, Risley D, Anenberg SC, Hubbell BJ. 2012a. “Estimating the National Public Health 

Burden Associated with Exposure to Ambient PM2.5 and ozone. Risk Analysis,” Risk Analysis 32(1): 81-95.

Levy JI, Baxter LK, Schwartz J. 2009. “Uncertainty and variability in health-related damages from coal-fired power 

plants in the United States.” Risk Analysis 29(7) 1000-1014.

Pye, J.M. 1988. Impact of ozone on the growth and yield of trees: A review. Journal of Environmental Quality, 17, 

347-360.

Tagaris E, Liao KJ, Delucia AJ, et al. 2009. “Potential impact of climate change on air-pollution related human 

health effects.” Environmental Science & Technolology 43: 4979–4988.

U.S. Environmental Protection Agency (U.S. EPA). 2013. Integrated Science Assessment of Ozone and Related

Photochemical Oxidants (Final Report). EPA-600/R-10/076F. February. Available on the Internet at 

http://cfpub.epa.gov/ncea/isa/recordisplay.cfm?deid=247492.

U.S. Environmental Protection Agency (U.S. EPA). 2014a. Control of Air Pollution from Motor Vehicles: Tier 3 

Motor Vehicle Emission and Fuel Standards. Office of Transportation and Air Quality. Available at 

http://www.epa.gov/otaq/tier3.htm.

U.S. Environmental Protection Agency (U.S. EPA). 2014b. Proposed Carbon Pollution Guidelines for Existing 

Power Plants and Emission Standards for Modified and Reconstructed Power Plants. Available at 

http://www2.epa.gov/sites/production/files/2014-06/documents/20140602ria-clean-power-plan.pdf

U.S. Environmental Protection Agency. 2014c. Policy Assessment for the Review of the Ozone NAAQS, Final 

Report. August. Available on the Internet at 

http://www.epa.gov/ttn/naaqs/standards/ozone/data/20140829pa.pdf.