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Analysis of State­ and County­Level PM2.5 Benefits

Overview

The Regulatory Impact Analysis (RIA) accompanying the recently proposed Toxics Rule 

summarized the national and regional PM2.5‐related health co‐benefits associated with the rule 

(EPA, 2011). Due to data, time and resource constraints, EPA did not report these co‐benefits at a 

sub‐regional level. In this Technical Support Document (TSD) we describe our approach for 

allocating the national‐level PM2.5‐related monetized benefits to the state, and the county‐level 

avoided premature deaths to the county. We also summarize the results of this analysis and 

describe the limitations and uncertainties associated with our approach. A key limitation of our 

approach is that it does not completely account for PM2.5 transport between states, and so may 

under‐ or over‐estimate PM‐related co‐benefits for certain states. 

Methodology

As noted in the RIA, the air quality modeling scenario used in developing national benefits 

estimates for the Toxics Rule reflected an early assessment of the potential utility emissions 

controls, and as a result, the projected estimates of ambient PM2.5 did not match the expected level 

and spatial distribution of PM2.5 levels resulting from the specific emissions changes that are 

associated with implementation of the actual proposed rule; time limitations prevented EPA from 

modeling the air quality changes associated with emissions controls estimated to result from the 

proposed rule. For this reason, in estimating the national total PM2.5 related benefits of the 

proposed rule, EPA applied a benefit per‐ton approach, in which it scaled the PM2.5 co‐benefits 

estimated from the air quality modeled scenario based on the relative national levels of SO2 

emission reductions; this procedure is described in the PM2.5 co‐benefits chapter of the RIA. A key 

limitation of the benefit‐per ton approach is that it generally provides a very limited 

characterization of the benefits at a sub‐regional (i.e. state or county) scale. However, spatially 

resolved estimates of the co‐benefits are clearly very useful to understanding how the expected 

benefits of this rule are distributed across the U.S. 

The spatial resolution of the input data to the benefits calculations affected the scale at which we 

could report the monetized benefits and premature deaths. For example, estimates of premature 

death were calculated in BenMAP (prior to the scaling exercise) using a combination of national and 

county data, which gives us greater confidence in reporting county‐level results. The total 

monetized benefits were calculated using a combination of national, regional and county‐level data, 

giving us greater confidence in reporting state‐level results. 

For this reason, EPA developed an approximation approach for allocating the national‐level PM2.5

co‐benefits estimated in the Toxics Rule RIA to the state and county level. Below we first summarize 

our approach for calculating state‐level monetized benefits and then detail our methods for 
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estimating the number of premature deaths avoided at each county. This approach is subject to 

important uncertainties, which we also describe below. 

Allocating the national‐level PM2.5 monetized co‐benefits to the state‐level

EPA followed the sequence of steps below to allocate the national‐level PM2.5 monetized co‐benefits 

to each state. 

1. Estimate the state­level monetized co­benefits of the air quality modeled scenario. Using the 

environmental Benefits Mapping and Analysis Program (Abt, 2008), EPA quantified the 

total monetized PM2.5‐related co‐benefits of the air quality modeled scenario for each state. 

The methods for estimating the monetized benefits of changes in PM2.5 air quality levels are 

detailed in the co‐benefits chapter of the RIA. 

2. Calculate the percentage change in state­level SO2 reductions between the modeled and

proposed policy cases. There were significant changes in both the size and distribution of SO2

emission reductions between the modeled and proposed policy case; this step accounts for 

the percentage change in SO2 reductions for each state.1

3. Scale the state­level monetized co­benefits according to the percentage change in SO2

emissions between the air quality modeled and final policy cases. In this final step, the state‐

level monetized co‐benefits estimated in step 1 is adjusted according to the percentage 

calculated in step 2. 

Allocating the national‐level avoided PM2.5 premature deaths to the county‐level

EPA followed the sequence of steps below to allocate the national‐level avoided PM2.5 premature 

deaths to each county. 

1. Estimate the number of avoided PM2.5­related premature deaths of the air quality modeled

scenario for each county. Using the environmental Benefits Mapping and Analysis Program

(Abt, 2008), for each county EPA quantified the number of PM2.5‐related premature deaths 

avoided resulting from the air quality modeled scenario. The methods for estimating the 

number of avoided PM2.5‐related deaths are detailed in the co‐benefits chapter of the RIA. 

2. Calculate the percentage change in state­level SO2 reductions between the modeled and

proposed policy cases. There were significant changes in both the size and distribution of SO2

emission reductions between the modeled and proposed policy case; this step accounts for 

the percentage change in SO2 reductions for each state. 

                                                           

1 The Toxics Rule changed the level and distribution of PM2.5 precursors, including SO2, NOx and directly‐emitted

PM2.5. However, as we describe in the RIA, we scaled the PM2.5‐related benefits of changes in SO2 emissions alone

for three reasons: (1) the great majority of the emission reductions were of SO2; (2) changes in directly PM2.5

resulted in relatively small benefits overall; (3) the complex and non‐linear chemistry governing nitrate PM

formation made it challenging to generate a benefit per‐ton estimate for this precursor.
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3. Scale the county­level avoided PM2.5 deaths according to the percentage change in SO2

emissions between the air quality modeled and final policy cases for each state. In this final 

step, the number of PM2.5 related deaths avoided in each county in step 1 is adjusted 

according to the percentage change in SO2 emissions for that state calculated in step 2. 

Limitations and uncertainties

The method described above adds unique uncertainties and limitations beyond those already 

described in detail in the co‐benefits chapter: 

1. This approach does not account fully for the transport of PM2.5 between states. This method 

assumes that the PM2.5‐related monetized benefits and avoided deaths are proportional to 

the change in PM2.5 precursors in that state. However, emission changes in one state affect 

the PM2.5 levels in neighboring states. As a result, we may under‐ or over‐estimate the PM2.5

monetized benefits and avoided mortalities in each state. 

2. This approach does not account for the transport of PM2.5 within states. This method assumes 

that the number of avoided deaths in each county within each state scales according to the 

change in emissions between the air quality modeled and policy case in that state. As a 

result, this method does not account for the fact that the location of emissions within the 

state are likely to also change, which would affect the number of avoided deaths in each 

county. 

3. States in which no SO2 emissions are reduced are allocated no benefits. For Kentucky we 

estimate no change in PM‐related deaths or monetized benefits due to the fact that the final 

policy scenario did not apply any SO2 emission controls to units in Kentucky; this reflects 

the results of a recent settlement with the Tennessee Valley Authority that went into effect 

after the completion of the air quality modeling but before the rule was proposed. However, 

because upwind states have significantly reduced SO2 emissions, we expect Kentucky to 

receive significant PM2.5‐related co‐benefits under the proposed rule. 

Results

Below we report the PM2.5‐related monetized co‐benefits in each state (Table 1). We also provide a 

map of the monetized co‐benefits in each state (Figure 1) and the number of PM2.5‐related deaths 

avoided in each county (Figure 2). 

   
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Table 1: Estimated PM2.5­related Monetized Co­Benefits for Each State

State 

Total Monetized Benefits

(3% discount rate, millions of 2007$)

Pope et al. (2002) mortality estimate Laden et al. (2006) mortality estimate

Alabama $1,600 $3,900 

Arizona $400 $1,000 

Arkansas $1,200 $2,800 

California $580 $1,400 

Colorado $410 $990 

Connecticut $2,400 $5,900 

Delaware $250 $620 

DC $130 $320 

Florida $4,700 $12,000 

Georgia $880 $2,100 

Idaho $18 $45 

Illinois $1,900 $4,600 

Indiana $1,100 $2,600 

Iowa $550 $1,300 

Kansas $680 $1,700 

Kentucky ---A ---A

Louisiana $1,300 $3,300 

Maine $75 $180 

Maryland $1,300 $3,200 

Massachusetts $2,700 $6,700 

Michigan $2,400 $5,800 

Minnesota $580 $1,400 

Mississippi $480 $1,200 

Missouri $1,400 $3,500 

Montana $75 $190 

Nebraska $320 $790 

Nevada $17 $43 

New Hampshire $200 $490 

New Jersey $6,700 $16,000 

New Mexico $100 $250 
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New York $5,100 $12,000 

North Carolina $1,700 $4,100 

North Dakota $79 $190 

Ohio $2,700 $6,700 

Oklahoma $1,100 $2,600 

Oregon $11 $28 

Pennsylvania $3,300 $8,200 

Rhode Island ---A ---A

South Carolina $1,800 $4,400 

South Dakota $130 $320 

Tennessee $2,500 $6,200 

Texas $8,800 $22,000 

Utah $94 $230 

Vermont ---A ---A

Virginia $2,000 $4,900 

Washington ---A ---A

West Virginia $650 $1,600 

Wisconsin $1,300 $3,100 

Wyoming $16 $38 

A While methodological limitations prevented us from estimating PM2.5-related benefits in these 

states, emission reductions from neighboring states are likely to provide PM2.5-related benefits.