The Health and Related Economic Benefits 

of Attaining 

Healthful Air in the San Joaquin Valley

Jane V. Hall, Ph.D.

Victor Brajer, Ph.D.

California State University

Fullerton, CA 

Frederick W. Lurmann

Sonoma Technology, Inc.

Petaluma, CA

March 2006

Research funded by the William and Flora Hewlett Foundation
1

The Health and Related Economic Benefits of Attaining 

Healthful Air in the San Joaquin Valley

Acknowledgements and Disclaimer 2

Acronyms 3

I. Executive Summary 4

II. Introduction 7

II.1 Background 7

II.2 Objectives of this Study 7

II.3 Overview of Approach 7

III. Population Exposure to Ozone and Particulate Matter 9

III.1 The Exposure Assessment Approach 9

 III.2 Population 10

III.3 Current Ambient Air Quality 13

III.4 Future Ambient Air Quality 15

III.5 Current and Future Population Exposure Estimates 16

IV. Adverse Ozone and PM-Related Health Effects 51

IV.1 Studies Used in Quantification of Effects 51

IV.2 Estimates of Reduced Adverse Effects with Attainment of the Federal AQS 58

V. Economic Valuation 64

V.1 The Basis for Value

V.2 Concepts and Measures of Value 64

V.3 Specific Values for Premature Death 64

V.4 Specific Values for Health Endpoints 67

V.5 Estimated Economic Value from Reduced Adverse Health Effects with 

Attainment of the Federal Air Quality Standards 71

VI. Conclusions and Implications 74

VII. References 76

Appendix

A.1 The Benefits of Attaining the California Air Quality Standards 82

A.2 Sensitivity Analysis by Endpoint 84 
2

ACKNOWLEDGMENTS

The authors thank the William and Flora Hewlett Foundation for funding this research. 

We also thank The California Endowment for supporting dissemination of the results. For their 

contributions to the research, we thank Siana Alcorn and Brian Penfold of Sonoma Technology, 

Inc., and Cheryl Paul of the Central Valley Health Policy Institute at California State University, 

Fresno. We also thank Danielle Deane and Carole Chamberlain for their encouragement and 

support.

All statements and conclusions in this study are solely those of the authors. 
3

ACRONYMS

ARB California Air Resources Board

CAAQS California Ambient Air Quality Standards

COI Cost of illness

C-R Concentration response function

EPA Environmental Protection Agency

FRM Federal Reference Method

MRAD Minor restricted activity day

NAAQS National Ambient Air Quality Standards

ppb Parts per billion

ppm Parts per million

REHEX Regional Human Exposure Model

SAB-HEES Science Advisory Board Health and Ecological Effects 

Subcommittee

SJVAB San Joaquin Valley Air Basin

SYMVAL Symptom Valuation Model

VSL Value of a statistical life

WLD Work loss day

WTP Willingness to pay
4

I. EXECUTIVE SUMMARY

Overview

Only the Los Angeles and Houston regions have air pollution levels that rival those in the 

San Joaquin Valley (SJV). Historical and current air quality levels for ozone and fine particles 

(PM2.5 ) in the San Joaquin Valley (SJV) are unhealthful. The air basin is classified by the U. S. 

Environmental Protection Agency (EPA) as a serious nonattainment area for both ozone and 

PM2.5 . 

Both the federal government and California have set health-based air quality standards 

for ozone and fine particles because there is wide concurrence that these pollutants pose a serious 

risk to health. Adverse effects clearly associated with ozone range from school absences and 

hospitalizations to symptoms that limit normal daily activity. PM2.5 exposure is tied to a range 

of effects from premature death and the onset of chronic bronchitis to work loss days and 

respiratory symptoms.

Between 1990 and 2004 ambient ozone levels in the San Joaquin Valley exceeded the 

health-based 8-hour National Ambient Air Quality Standard (NAAQS) on from more than 80 to 

nearly 135 days a year. Ozone levels are typically elevated in the summer months, so this 

suggests that air is unhealthful on most summer days. Not only is the NAAQS frequently 

violated, but between 2001 and 2004 the maximum 8-hour concentration was 65% above the 

standard. In much of California ozone levels have fallen steadily over a period of years, but this 

is not the case in the SJV, which is a concern.

While the region has achieved reductions in coarser particle (PM10) levels, concentrations 

of the more dangerous fine particles - PM2.5 - remain unhealthful. To meet the maximum 24-

hour standard levels must fall by more than 10%, and annual average concentrations must fall by 

nearly 30%. Attaining the California standard (CAAQS) requires a drop of 50%. These healthbased standards will be very difficult to achieve in the SJV.

The primary objective of this study is to assess the health and related economic benefits 

that will result from attainment of the ozone and PM2.5 standards, to the extent that they can be 

quantified.

Results

Valley-wide, the economic benefits of meeting the federal PM2.5 and ozone standards 

average nearly $1,000 per person per year, or a total of more than $3 billion. This gain 

represents the following:

• 460 fewer premature deaths among those age 30 and older

• 325 fewer new cases of chronic bronchitis

• 188,400 fewer days of reduced activity in adults

• 260 fewer hospital admissions

• 23,300 fewer asthma attacks
5

• 188,000 fewer days of school absence

• 3,230 fewer cases of acute bronchitis in children

• 3,000 fewer work loss days

• More than 17,000 fewer days of respiratory symptoms in children

To place the reduction in premature deaths in perspective, attaining the federal PM2.5 

standard would be the equivalent of reducing motor vehicle deaths by over 60% Valley-wide, 

and by more than 70% in Fresno and Kern Counties.

Research Approach

A well-established three-stage approach is used to determine the benefits of attaining the 

ozone and PM2.5 air quality standards by identifying and quantifying the links between air 

quality and exposure, exposure and ill health, and avoiding ill health and the associated 

economic loss.

The Regional Human Exposure Model (REHEX) was developed to estimate a 

population’s exposure to concentrations above the air quality standards. This model accounts for 

the spatial and temporal pollution patterns across a region, which is important because pollution 

patterns vary significantly across a large area. Exposure for the population in the SJV is 

estimated by 5X5 kilometer grids relative to pollution levels averaged from 2002-2004. 

Averaging is necessary to reduce the influence of weather anomalies that do not accurately 

represent longer term trends in air quality. REHEX generates estimates of exposure by county, 

by age, and by ethnic group as defined by the U.S. Bureau of the Census. These exposure 

estimates are then coupled with concentration-response functions from the health science 

literature to calculate how many fewer adverse health effects and premature deaths would be 

expected if the 2004 population instantaneously experienced attainment of the NAAQS.

Finally, economic values are applied to the avoided health effects and extended lives to 

estimate in dollar terms the social value of more healthful air. These values are based on the cost 

of treating illness and the expressed value that people place on avoiding illness and premature 

death.

Implications

Residents of the San Joaquin Valley face significant public health risks from the present 

unhealthful levels of ozone and fine particles. This is in addition to other health challenges, 

including a high rate of poverty, which exceeds 30% in Fresno County, compared to a statewide 

rate below 20%. The region overall would experience substantial economic and health gains 

from effective policies to reduce pollution levels. For the more populous and more polluted 

areas in Kern and Fresno Counties, this is even more pronounced. Attaining the California air 

quality standards, which are more protective of health, would double the benefits listed above.

The adverse impacts of air pollution are not distributed equally. Both Hispanics and nonHispanic blacks are exposed to more days when the health-based standards are violated. 
6

Residents of Fresno and Kern Counties experience many more days than the Valley-wide 

average.

Because ozone is elevated during the summer months, and the PM2.5 24-hr standard is 

typically violated more frequently in the winter months, there is no “clean” season in this region.

As the population continues to increase, with associated increases in vehicle traffic and 

economic activity, the gains from attaining the health-based air quality standards will grow, but 

also become more difficult to achieve. Identifying and acting on opportunities now would 

produce substantial gains to the people of the Valley.
7

II. INTRODUCTION

II.1 Background

Only the Los Angeles and Houston regions have air pollution levels that rival those in the 

San Joaquin Valley (SJV). Historical and current air quality levels for ozone and fine particles 

(PM2.5 ) in the SJV are unhealthful. The air basin is classified by the U. S. Environmental 

Protection Agency (EPA) as a serious nonattainment area for both ozone and PM2.5 . 

Both the federal government and California have set health-based air quality standards 

for ozone and fine particles (PM2.5 ) because there is wide concurrence that these pollutants pose 

a serious risk to health. Adverse effects clearly associated with ozone range from school 

absences and hospitalizations to symptoms that limit normal daily activity. PM2.5 exposure is 

tied to a range of effects from premature death and the onset of chronic bronchitis to work loss 

days and respiratory symptoms.

Between 1990 and 2004 ambient ozone levels in the San Joaquin Valley exceeded the 

health-based 8-hour National Ambient Air Quality Standard (NAAQS) on from more than 80 to 

nearly 135 days a year. Ozone levels are typically elevated in the summer months, so this 

suggests that air is unhealthful on most summer days. Not only is the NAAQS frequently 

violated, but between 2001 and 2004 the maximum 8-hour concentration was 65% above the 

standard. In much of California ozone levels have fallen steadily over a period of years, but this 

is not the case in the SJV, which is a concern.

While the region has achieved reductions in coarser particle (PM10) levels, concentrations 

of the more dangerous fine particles - PM2.5 - remain unhealthful. To meet the maximum 24-

hour standard levels must fall by more than 10%, and annual average concentrations must fall by 

nearly 30%. Attaining the California standard (CAAQS) requires a drop of 50%. These healthbased standards will be very difficult to achieve in the SJV.

II.2 Objectives of this Study

The primary objective of this study is to assess the health and related economic benefits 

that will result from attainment of the ozone and PM2.5 standards, to the extent that they can be 

quantified with present knowledge. The gains from attaining both the federal and state standards 

are estimated, although it is generally recognized that attaining the state standards will be 

especially difficult in some parts of the SJV1.

II. 3 Overview of the Research Approach

A well-established three-stage approach is used to determine the benefits of attaining the 

ozone and PM2.5 air quality standards by identifying and quantifying the links between air 

quality and exposure, exposure and ill health, and avoiding ill health and the associated 

economic loss.

 1 Because attainment of the NAAQS is therefore the more policy-relevant outcome over the next decade, the 

California results are included in the Appendix while the Federal results are discussed in the body of this report.
8

The Regional Human Exposure Model (REHEX) was initially developed in 1989 to 

estimate a population’s exposure to concentrations above the air quality standards. This model 

accounts for the spatial and temporal pollution patterns across a region, which is important 

because pollution patterns vary significantly across a large area. Here, exposure for the 

population in the SJV is estimated by 5X5 kilometer grids relative to pollution levels averaged 

from 2002-2004. Averaging is necessary to reduce the influence of weather anomalies that do 

not accurately represent longer term trends in air quality. REHEX generates estimates of 

exposure by county, by age, and by ethnic group as defined by the U.S. Bureau of the Census. 

These exposure estimates are then coupled with concentration-response functions from the health 

science literature to calculate how many fewer adverse health effects and premature deaths 

would be expected if the 2004 population instantaneously experienced attainment of the NAAQS 

and the CAAQS.

Finally, economic values are applied to the avoided health effects and extended lives to 

estimate in dollar terms the social value of more healthful air. Specific values are derived from 

the economics literature and have all undergone peer-review, both as part of that literature and as 

part of scientific and technical assessments of which values are most appropriate for valuing 

health in relation to air pollution exposure.
9

III. POPULATION EXPOSURE TO OZONE AND PARTICULATE MATTER

III.1 The Exposure Assessment Approach

Accurate estimates of human exposure to inhaled air pollutants are necessary for 

appraisal of the health risks these pollutants pose and for the design and implementation of 

strategies to control and limit those risks. Most exposure estimates are based on measured 

concentrations of outdoor (ambient) air concentrations obtained at fixed-site air monitoring 

stations. Ambient concentrations are used as surrogates for personal exposure. Personal 

exposure to air pollutants depends not only on ambient concentrations in locations or 

microenvironments (home, work, schools, vehicles, etc.) where individuals spend time, but also 

on the amount of time individuals spend in the microenvironments and on the concentrations in 

the microenvironments. Microenvironment concentrations are affected not only by infiltration of 

outdoor air, but also by indoor sources and indoor pollutant deposition. Outdoor concentrations 

vary spatially and temporally and are affected by proximity to local outdoor sources, which may 

result in concentrations that deviate significantly from ambient concentrations at the nearest air 

monitoring stations. 

Despite the recognized discrepancies between personal exposure and exposures based on 

ambient concentrations obtained from fixed-site air monitoring stations, compliance with the 

National Ambient Air Quality Standards (NAAQS) depends exclusively on outdoor 

measurements of pollutants. The NAAQS are intended to protect public health with an adequate 

margin of safety. Most epidemiologic studies of air pollution health effects use ambient 

concentrations as surrogates for actual population exposures. In fact, virtually all concentrationresponse relationships from large population studies use ambient concentrations as the exposure 

input parameter. Several studies have argued that air pollution exposure should be separated into 

ambient and non-ambient components for health effects research because even though ambient 

concentrations are not highly correlated with personal exposures to non-ambient concentrations 

or total concentrations, they are highly correlated with ambient-generated concentrations (Wilson 

et al. 2000; Ebelt et al. 2003). Therefore, ambient concentrations may be used in epidemiologic 

studies as appropriate surrogates for exposure to ambient-generated concentrations. 

The exposure assessment approach for this study is constrained to rely on ambient 

concentrations not only because the ambient air quality database is the only database with 

sufficient spatial and temporal coverage to address the San Joaquin Valley Air Basin (SJVAB)

population, but also because this study requires quantification of the benefits of attainment of the 

ambient-based NAAQS and must rely on the ambient-based concentration-response relationships 

from the health science literature to quantify those benefits. The approach is also guided by the 

concern for spatial resolution of both the population and ambient concentrations. 

The population exposure assessment approach used for this study involves representing 

the population and ambient concentrations on a spatial grid covering the SJVAB. Each grid 

square is 5 km x 5 km in size. Five-kilometer resolution is sufficient to capture the urban- and 

regional-scale spatial gradients in between air quality monitoring stations, which are located 

from 10 to 50 km apart in the SJVAB. This resolution is insufficient to capture intra-urban 

spatial variations associated with close proximity to major roadways or stationary emission 

sources. Spatially and temporally resolved air quality and population data are used in the 
10

Regional Human Exposure (REHEX) model (Lurmann et al. 1989; Lurmann et al. 1994; Fruin et 

al. 2001) to quantify the frequency of population exposure to various levels of ambient ozone 

and particulate matter concentrations over multi-year periods.

III.2 Population

We developed gridded population data for use in the exposure assessment for eight age 

groups: < 1 year, 1 year, 2-4 years, 5-17 years, 18-21 years, 22-29 years, 30-64 years, and > 64 

years, and four racial groups: white non-Hispanic, black non-Hispanic, other non-Hispanic, and 

Hispanic. The age groups were defined by the concentration-response relationships chosen for 

use in the benefits evaluation. Racial groups were defined by the U.S. Census. Not all the 

population data breakdowns by age and race were available at fine resolution in the 2000 U.S. 

Census database. County, census tract, and block-group levels of population data were used in 

determining the disaggregated block-group population data. County-level age distribution data 

were used to estimate the block-group population of children ages < 1, 1, and 2-4 years by racial 

group. Census-tract level data were used to estimate the block-group population of other age 

groups for black non-Hispanic and other non-Hispanic groups. Block-group data were used 

directly for the other age groups for white non-Hispanics and Hispanics. The block-group 

population data for each age-racial group were spatially allocated to 5 km x 5 km grid squares 

assuming uniform population density within each block group. The spatial allocation was 

performed with STI’s GIS tools (ESRI ARCGIS Version 9.0). Grids on the boundaries between 

counties were assigned to the county with the most surface area within the grid.

The modeling grid and gridded 2000 total population data are shown in Figure III-1. 

These data show that high population densities (> 1,200 km-2

) occur in the major cities, such as 

Lodi, Stockton, Modesto, Turlock, Fresno, Visalia, and Bakersfield, as expected. A total of 

1,708 grids located within the SJVAB were used for assessing exposure. Grid squares with 

extremely low population density (below 1 person per km-2 or 25 persons per grid) were not 

included; they were large in number of grids but accounted for less than 1% of the total 

population in the aggregate. 

The baseline period selected for exposure assessment was 2002 through 2004 (see 

Section III.3). Population data for 2000 were projected to 2004 to be consistent with the baseline 

period for air quality data. County-specific growth rates based on the growth from 1990 to 2000 

(as reported in the U.S. Census (www.censuscope.org)) were used to scale up the 2000 data to 

represent the 2004 population. Within each county, the population of all age and racial groups 

was scaled uniformly. The 2004 populations were estimated as 6.6, 7.8, 6.9, 14.3, 7.5, 10.2, 6.8, 

and 8.2% higher than the 2000 populations for San Joaquin, Stanislaus, Merced, Madera, Fresno, 

Kings, Tulare, and Kern Counties, respectively. The estimated total population in the region is 

3.34 million persons in 2004. As shown in Table III-1, about 25% of the residents live in Fresno 

County and another 35% lived in San Joaquin and Kern Counties. Adults, ages 30 to 64 years, 

are the largest age group (41%), followed by children ages 5 to 17 (23.5%). Likewise, as shown 

in Table III-2, whites and Hispanics are the largest racial/ethnic groups.

The SJVAB is experiencing high population growth; however, we have not included the 

likely population growth beyond 2004 in our estimates of the benefits of attaining air quality 

standards in the future. This approach is conservative in that it results in underestimation of the 
11

likely benefits and avoids having to specify when the region will actually reach its air quality 

goals. Because the population is growing at about 2% per year, the benefits are likely to be 16% 

to 20% greater than estimated if attainment is achieved in 8 to 10 years.

Estimates of the population of children attending school were also needed to determine 

the benefits of reduced school absences associated with air quality improvements. Public school 

enrollment and schedules for the 2005-2006 school year were obtained from SJVAB school 

districts. They indicated that 83.5% and 16.5% of public school children attended schools on 

traditional and year-round schedules, respectively. The majority of traditional school schedules 

extended for 91⁄2 months, from mid-August through May. Additional attendance data indicated 

that 4% of children, ages 5-17 years, attended private schools. We did not have private school 

schedules or information on summer school attendance for public or private schools. Because 

private school attendance was low, no distinction was made between the schedules of public and 

private school students. Ten percent of traditional-schedule school children were assumed to 

attend summer school, which is a low estimate based on our analysis of data for Southern 

California (Hall et al. 2003). The population of children, ages 5-17 years, attending school in the 

non-summer period (mid-August through May) was estimated at 96.6% based on the sum of 

children in schools with traditional schedules (83.5%) and year-round schedules (91⁄2 /12 x 

16.5%=13.1%). The population of children, ages 5-17 years, attending school in the summer 

period (June through mid-August) was estimated at 21.4% based on the sum of children in 

schools with year-round schedules (13.1%) and children with traditional school schedules who 

were attending summer school (8.3%). 
12

Table III-1. 2004 SJVAB population by county and age group.

Region <1 

Year 1 Year 2-4 

Years

5-17 

Years

18-21 

Years

22-29 

Years

30-64 

Years

>64 

Years All Ages

San Joaquin 

County 8,531 8,711 27,796 130,408 35,154 59,283 242,360 61,762 574,005

Stanislaus 

County 6,888 7,174 22,569 107,166 27,466 49,096 196,460 49,545 466,364

Merced 

County 3,695 3,766 12,084 56,898 13,956 23,726 87,393 21,109 222,627

Madera 

County 2,213 2,368 7,458 34,300 8,902 16,663 69,805 17,348 159,057

Fresno 

County 13,284 13,433 41,667 191,295 54,309 94,551 322,881 81,231 812,651

Kings 

County 2,136 2,155 6,525 28,336 8,921 19,533 59,417 10,211 137,234

Tulare 

County 6,706 6,538 20,750 95,226 24,841 42,301 150,254 37,576 384,192

Kern County 9,979 10,045 30,830 140,112 36,682 68,071 238,230 50,337 584,286

Air Basin 

(Persons) 53,432 54,190 169,679 783,741 210,231 373,224 1,366,800 329,119 3,340,416

Air Basin 

(Percent) 1.6% 1.6% 5.1% 23.5% 6.3% 11.2% 40.9% 9.9% 100%

Table III-2. 2004 SJVAB population by county and racial/ethnic groups.

Region Whitea Blacka Hispanic Othera Total

(Persons)

Total

(Percent)

San Joaquin County 279,855 38,694 182,293 73,163 574,005 17.2%

Stanislaus County 277,637 11,506 151,213 26,008 466,364 14%

Merced County 93,073 8,264 104,208 17,082 222,627 6.7%

Madera County 80,534 6,125 66,249 6,148 159,057 4.8%

Fresno County 324,342 42,887 370,591 74,831 812,651 24.3%

Kings County 58,828 10,991 61,403 6,012 137,234 4.1%

Tulare County 163,320 5,459 199,331 16,082 384,192 11.5%

Kern County 265,643 35,044 256,831 26,769 584,286 17.5%

Air Basin (persons) 1,543,201 158,968 1,392,180 246,066 3,340,416 100%

Air Basin (percent) 46.2% 4.8% 41.7% 7.4% 100%

a Non-Hispanic whites, blacks and other.
13

III.3 Current Ambient Air Quality

III.3.1 Current Conditions Relative to the Air Quality Standards

Historical and current ambient air quality conditions for ozone and particulate matter in 

the SJVAB are unhealthful. Concentrations exceed the health-based NAAQS and the more 

stringent California Ambient Air Quality Standards (CAAQS). The SJVAB is classified as a 

serious nonattainment area by the U.S. Environmental Protection Agency (EPA) for ozone and 

PM2.5. The most relevant NAAQS for ozone is the 8-hour daily maximum standard of 0.08 parts 

per million (ppm) or 80 parts per billion (ppb). It has essentially replaced the 1-hour daily 

maximum ozone standard of 0.12 ppm, which is less stringent2

The frequency and severity of exceedances of the 8-hour daily maximum ozone standard 

are illustrated in Figures III-2 and III-3. The SJVAB measurement data show that the ambient 

concentrations exceeded the level of the standard on 82 to 134 days per year between 1990 and 

2004. This high frequency indicates that most days during the summer were ozone exceedance 

days. Unlike other parts of California, the frequency of exceedances is not declining with time in 

the SJVAB, which is a concern for residents and government agencies. During the 2001-2004 

time period, the maximum 8-hour concentration was 132 ppb or 65% above the level of the 

standard. The highest 8-hour concentrations occur most frequently southeast of Bakersfield at 

the Arvin air monitoring station. Similarly high concentrations can occur downwind of Fresno. 

The 8-hour NAAQS is achieved when the three-year average of the annual fourth-highest 

concentration is below the level of the standard. The three-year average of the annual fourthhighest concentration was 116 ppb for 2002-2004 and 113 ppb for 2003-2005. This value is 

referred to as the ozone design value for the baseline period. We chose to use 2002-2004 for our 

baseline period because we wanted to use the same period for ozone and PM2.5, and annual PM2.5

data for 2005 were not available when we initiated this study. Thus, attainment of the 8-hour 

NAAQS is expected when the annual fourth-highest concentration is reduced from 116 ppb to 

84.99 ppb. Note, 84.99 ppb is used instead of 80 ppb because of agency guidance on rounding 

concentrations for compliance with the “0.08 ppm” standard. Attainment of the ozone standard 

requires a 27% decrease in the design value. However, because there is a global background 

concentration of about 40 ppb, the required reduction in ozone in excess of the background level 

is 41% to reach attainment. 

in the SJVAB. Federal standards 

exist for maximum 24-hour average and annual average PM2.5 and PM10. The 65 μg/m3 24-hour 

PM2.5 standard and 15 μg/m3 annual PM2.5 standard are generally more stringent than the 150 

μg/m3 24-hour PM10 standard and 50 μg/m3 annual PM10 standard. The SJVAB will reach 

federal attainment when the more stringent federal standards are reached. Thus, this study 

focuses on the 8-hour ozone standard and the 24-hour and annual average PM2.5 standards. 

Compliance with the California standards (a 70 ppb 8-hour daily maximum ozone and a 12 

μg/m3 annual average PM2.5 standard) is addressed in the appendix.

Even though the region achieved compliance with the PM10 NAAQS in the 2003-2005 

time period, PM2.5 air quality conditions remain unhealthful. Figure III-4 shows the 98th

percentile 24-hour average and the annual average PM2.5 concentration in 2002-2004 at key 

 2 Here, stringent means more limiting in terms of the difficulty of attainment.
14

monitoring stations. The highest 24-hour average PM2.5 concentration in 2002 was 91 μg/m3 at 

Corcoran, which is 40% above the level of the standard. The highest annual average 

concentration in 2002 was 24 μg/m3 in Bakersfield at the Golden State Highway air monitoring 

station, where the 24-hour maximum was also high (85 μg/m3). High PM2.5 concentrations were 

also observed in the middle portion of the SJVAB as indicated by the data for Fresno, Visalia, 

and Corcoran. High 24-hour concentrations tend to occur in the fall and winter in this area. Like 

the ozone standard, the PM2.5 standards are based on three-year periods. The annual PM2.5

NAAQS is achieved when the three-year averaged annual mean PM2.5 concentration is less than 

or equal to 15 μg/m3. The 24-hour PM2.5 standard is achieved when the three-year average of the 

annual 98th percentile values at each PM2.5 monitoring site is less than or equal to 65 μg/m3. The 

PM2.5 design values are 20.6 and 73.2 μg/m3 for the annual average and 24-hour standards, 

respectively. The design values are based on data from Bakersfield for the 2002-2004 baseline 

period. It should be noted that EPA’s PM2.5 attainment document suggests a lower 24-hour 

design value for this area, but we believe that 73.2 μg/m3 is the correct value because it is based 

on the exact same data that were used to determine the 20.6 μg/m3 annual average (also cited by 

EPA). The current design values indicate that maximum 24-hour and annual averages need to 

decrease by 11% and 27% to achieve compliance with the federal standards. The San Joaquin 

Valley Air Pollution Control Agency is charged with developing an air quality management plan 

by 2008 that will result in attainment of the PM2.5 NAAQS by 2013.

California has an annual average PM2.5 standard of 12 μg/m3, never to be exceeded. 

Compliance with this standard would require the 2002 annual concentration of 24 μg/m3 in 

Bakersfield be reduced by 50%. This health-based standard will be very difficult to achieve in 

the SJVAB. 

III.3.2 Spatial Mapping

Ambient air quality data from California’s network of monitoring stations were used to 

spatially map concentrations to the exposure grids. Measured concentration data were spatially 

interpolated and extrapolated to provide estimates of concentrations at each grid shown in 

Figure III-1. The locations of air monitoring stations on the exposure grid are shown in 

Figure III-5. For the 2002-2004 baseline period, hourly ozone data were available for 27 stations 

within the SJVAB and daily PM2.5 data were available once every three days for 14 stations 

within the SJVAB. Ozone and PM2.5 data from stations within the grid and within 150 km of the 

grid boundaries were incorporated in the air quality database used for mapping. The ozone data 

were used to create maps of hourly concentrations for each day of the baseline period 

(1,096 days and 26,304 maps). Daily PM2.5 data collected using the Federal Reference Method 

(FRM) were available on an every-day basis at several sites and on an every-third-day sampling 

schedule at many more sites. Spatial mapping was not feasible using data only from sites with 

every-day sampling. The spatial mapping of daily PM2.5 concentrations was performed using the 

FRM data on days when the every-third-day data were available in addition to the every-day data 

(~116 days per year). Annual average PM2.5 concentrations were calculated from the FRM data 

using EPA’s methodology (i.e., annual average = average of quarterly averages) and mapped for 

each year. 
15

The spatial mapping method assigns exposure grid concentrations from the nearest 

station if the station is located within 3 km of the center of the exposure grid. If no stations with 

valid data are located with 3 km of the center of the exposure grid, the concentration is calculated 

by inverse-distance squared weighting of the concentrations from the four stations closest to the 

center of the exposure grid, provided all stations are located within 100 km of the exposure grid 

center. In areas with sparse network coverage, the algorithm may be applied with fewer than 

four stations (i.e., one to three stations). This method is very similar to the method used by EPA 

on its AIRNow web site (www.epa.gov/airnow) for mapping air quality indices. Examples of 

the maps created with this method are shown in Figure III-6. They show the spatially mapped 

annual average PM2.5 concentrations for 2002, 2003, and 2004. The annual PM2.5 concentrations 

are estimated to vary smoothly across the region, with higher concentrations in the southern 

regions and in the urban areas. The maps of daily PM2.5 and hourly ozone maps often have more 

spatial variability than these examples because they reflect the day-to-day variations in 

meteorological conditions that greatly influence the spatial patterns. The ozone maps also reflect 

the greater spatial coverage of monitoring station data for ozone than for PM2.5.

III.4 Future Ambient Air Quality

For purposes of this exposure analysis, we are interested in the spatial and temporal 

distribution of ambient concentrations for a three-year period in which the air quality standard is 

attained. Attainment of the standard means that the design value is reduced to the level of the 

standard. Two methods are available to estimate future-year air quality conditions. One method 

involved the application of detailed meteorological, emissions, and air quality models to estimate 

the distributions of future concentrations under specific emission scenarios. Such models are 

used to develop emission control strategies to reach attainment in the air quality plans. 

Typically, the detailed models are applied for relatively short periods (less than two weeks per 

episode) rather than multi-year periods. The resources (time and budget) required to apply this 

method for a three-year period in the SJVAB are far greater than available for this study; hence, 

this method is not feasible for the present study. 

The second method involves the application of the simple linear rollback model shown 

below.

( ) 















−

− = + −

Max Bkgrd

Std Bkgrd

Bkgrd

Base

Bkgrd xyt

Future

xyt C C

C C

C C C C if Bkgrd

Base Cxyt ≥ C (1)

Base

xyt

Future Cxyt = C if Bkgrd

Base Cxyt < C (2)

where Future Cxyt = the future concentration at location x,y, and time t,

Base Cxyt = the baseline period concentration at location x,y, and time t,

CBkgrd = the background concentration, 

CMax = the design value concentration, and 

CStd = the air quality standard threshold concentration. 
16

This method assumes that future changes in concentrations in excess of the background 

concentration will linearly track changes in the current or baseline maximum concentration 

(minus the background concentration). It assumes that concentrations in excess of the 

background concentration with attainment will be linearly reduced in proportion to the ratio of 

the standard (adjusted for background) to the design value (also adjusted for background). 

Concentrations at or below the background level are assumed to be unaffected by changes in 

emissions. The rollback model is a very simple air quality model that ignores much of the 

detailed knowledge of the atmospheric chemistry and physics that influence concentrations, yet it 

is probably the most suitable model when the specific emission control measures needed to reach 

attainment in a region are not yet identified. The reason is that attainment can be achieved with 

different sets of control measures that will produce different spatial and temporal patterns of 

concentrations; and without knowledge of the specific path to attainment in the SJVAB, it is best 

to keep the projection method as simple as possible. 

The parameters used to project the distributions of concentrations with attainment are 

shown in Table III-3. They project that future ozone levels in excess of the background would 

be 59% of current levels. Similarly, the future 24-hour and annual PM2.5 concentrations in 

excess of the background are estimated as 89% and 65% of current levels. These factors are 

applied to the spatially mapped baseline-period concentrations to generate the future-year spatial 

maps of concentrations for the same time period (three years). 

Table III-3. Parameters used to estimate ambient ozone and PM2.5 concentrations with 

attainment.

Pollutant/Parameter Design Value Attainment 

Level

Background 

Concentration

Ozone 8-hour daily Maximum NAAQS 116.7 ppb 84.99 ppb 40 ppb

Ozone 8-hour daily Maximum CAAQS 132.5 ppb 74.99 ppb 40 ppb

PM2.5 24-hour Average NAAQS 73.2 μg/m3 65.49 μg/m3 6 μg/m3

PM2.5 Annual Average NAAQS 20.6 μg/m3 15.49 μg/m3 6 μg/m3

PM2.5 Annual Average CAAQS 24.1 μg/m3 12.49 μg/m3 6 μg/m3

III.5 Current and Future Population Exposure Estimates

The REHEX model was applied using population and air quality data for the SJVAB to 

estimate the population exposure to ozone and PM2.5 in the baseline period and the future with 

attainment. The population exposure to air pollution was quantified not only in terms of the 

exposure metrics relevant to the air quality standards, but also in terms of the exposure metrics 

used in the concentration-response relationships reported in the health science literature. The 

exposure metrics for ozone include the 1-hour daily maximum, the 2-week average 1-hour daily 

maximum, the 5-hour daily maximum, the 8-hour daily maximum, and the 24-hour average 

concentrations. Certain concentration-response relationships use 8-hour 10 a.m. to 6 p.m. ozone 

rather than 8-hour daily maximum ozone; the two metrics are almost indistinguishable in the 
17

SJVAB. The exposure metrics for PM2.5 include the 24-hour average concentration and the 

annual average concentrations. 

Most of the concentration-response relationships used in this study apply to all days of 

the year. The school-absence concentration-response relationship applies to exposures on the 

day preceding the school absence. For this analysis, exposures occurring on Fridays and 

Saturdays were excluded as well as the day preceding each holiday.

III.5.1 Exposure Frequency Distributions

The overall frequency distributions of daily exposure for the SJVAB population are 

shown in Figures III-7 through III-12. The total number of person-days of exposure is large for 

this region and time period, 1.2 billion per year (3.34 million x 365 days), so the distributions are 

presented on a logarithmic scale. The figures show the number of person-days of exposures per 

year to concentrations above various concentration thresholds. They illustrate a four to five 

order of magnitude difference between the person-days of exposure to the highest levels 

observed in the SJVAB and the person-days of exposure to levels above the background 

concentrations. Figure III-13 shows the estimated number of persons exposed to annual average 

PM2.5 concentrations above various concentration thresholds in the SJVAB. The daily and 

annual distributions show large differences in the frequency of exposure between the baseline 

and NAAQS attainment scenario. 

III.5.2 Spatial Distributions of Exposure

The estimated spatial distribution of exposure to ozone concentrations above 100, 85, and 

70 ppb are shown in Figure III-14 through III-16. They show that the highest number of persondays of exposure occur in and around Bakersfield, Fresno, Visalia, Merced, and Turlock in the 

2002-2004 period. The size of the region with more than 300,000 person-days of exposure per 

year per grid greatly increases as the exposure concentration threshold increases from 70 to 

85 ppb and from 85 to 100 ppb. The maps also show a dramatic decrease in estimated exposures 

above 85 ppb under the 8-hour ozone NAAQS attainment scenario. No exposures above 85 ppb 

are estimated for most of the SJVAB with attainment; only residents in and around Fresno, and 

downwind of Bakersfield are estimated to have about one day of exposure per year above the 

statistically based 8-hour NAAQS threshold of 85 ppb with attainment.

Maps of the estimated population exposure to 24-hour average PM2.5 concentrations 

above 65 and 40 μg/m3 are shown in Figures III-17 and III-18. The 40 μg/m3 threshold is used 

here because it is the daily PM2.5 threshold for sensitive groups. The maps show that the number 

of exposures above 40 and 65 μg/m3 in Bakersfield, Fresno, Visalia, and Modesto are higher 

than elsewhere. Residents in these urban areas are estimated to have one or two days per year of 

exposure to PM2.5 concentrations above 65 μg/m3 with attainment of the 24-hour NAAQS. 

The spatial distributions of population exposures to annual average PM2.5 concentrations 

above 18, 15, and 12 μg/m3 are shown in Figure III-19 through III-21, respectively. The number 

of residents estimated to be exposed to annual average PM2.5 concentrations above 15 μg/m3 is 

greater in Fresno, Visalia, and Bakersfield than elsewhere in the SJVAB. With attainment of the 

NAAQS, the area with residents exposed to concentrations above 15 μg/m3 shrinks substantially 
18

from that in the baseline period. However, the number of exposures and size of areas where 

residents are exposed to concentrations above 12 μg/m3—a level considered more protective of 

public health than 15 μg/m3

—are quite similar in the baseline and NAAQS attainment cases. 

III.5.3 Exposure Frequency by County, Age Group, and Racial/Ethnic Group

III.5.3.1 8-hour Daily Maximum Ozone Exposures

The estimated number of exposures to 8-hour daily maximum ozone concentrations 

above 70, 85, and 100 ppb are listed in Table III-4 for the individual counties and for the whole 

air basin. The REHEX model estimates 10 million, 69 million, and 235 million person-days of 

exposures per year to 8-hour concentrations above 100, 85, and 70 ppb, respectively, in the air 

basin in the baseline period. With NAAQS attainment, the estimated person-days of exposures 

per year above 85 ppb decrease from 69 million to 293 thousand in the air basin. The estimated 

exposures above 70 ppb decrease from 235 million to 34 million with attainment. Zero 

exposures to 8-hour ozone above 100 ppb are estimated with NAAQS attainment. The highest 

number of exposures to ozone above 85 ppb is estimated to occur in Fresno County where there 

are 25 million person-days in the baseline period and 211 thousand person-days with attainment. 

These changes represent large reductions in unhealthful ozone exposures. 

When these results are normalized by the population, they indicate the average number of 

days per year that residents are exposed to ambient concentrations above various thresholds. 

Table III-5 shows that the number of days per year above 100, 85, and 70 ppb 8-hour daily 

maximum ozone is estimated as 3, 21, and 70 days for the entire air basin population in 2002-

2004. In Kern and Fresno Counties, residents are estimated to be exposed to more than 85 ppb 

8-hour daily maximum ozone concentrations on 31 and 34 days per year on average, 

respectively. In contrast, residents of San Joaquin and Stanislaus Counties are estimated to be 

exposed to more than 85 ppb 8-hour ozone on 0 and 5 days per year, respectively, in the baseline 

period. The average number of days per year with population exposure to 8-hour ozone above 

70 ppb in the baseline period is 10, 29, 67, 81, 94, 79, 100, and 106 days in San Joaquin, 

Stanislaus, Merced, Madera, Fresno, Kings, Tulare, and Kern Counties, respectively, and 70 in 

the air basin, on average. With NAAQS attainment, the average number of days of population 

exposure above 85 and 70 ppb is estimated to be less than 1 and 10 days, respectively, for the air 

basin population.

Table III-6 and III-7 show the number of person-days and days of exposure to the 8-hour 

ozone concentration thresholds by age group. Because the age distributions are fairly similar 

across the region, the estimated number of days above 70 and 85 ppb is similar for the different 

age groups. Even without consideration of human time activity, the model results indicate 

children are exposed slightly more frequently than adults over age 30 in the SJVAB. For 

example, children under age 5 are exposed to ozone above 70 ppb on 72 days per year compared 

to 68 days per year for adults over age 64.

Table III-8 and III-9 show the number of person-days and days of exposure to the 8-hour 

ozone concentration thresholds by racial/ethnic group. The results show that Hispanics are 

exposed more frequently than other racial groups to 8-hour ozone levels above 70 and 85 ppb. 
19

For example, the estimated number of days above 85 ppb is 18, 19, 20, and 23 days per year for 

other races, blacks, whites, and Hispanics, respectively, in the air basin. Spatial differences in 

the population racial/ethnic makeup for different counties and within counties are responsible the 

differences in exposure frequencies. Figure III-22 and III-23 illustrate the differences in 

estimated frequency of exposures by ethnic/racial group within the air basin and by ethnic/racial 

group within each county. They show that the ranking of exposure frequencies by ethnic/racial 

group varies considerably by county. For example, in Merced and Madera Counties, black and 

other non-white racial groups have slightly higher exposure frequencies than whites and 

Hispanics.

III.5.3.2 One-hour, 5-hour, and 24-hour Ozone Exposures

Population exposure to ozone was also estimated for 1-hour and 5-hour daily maxima and 

24-hour average for use in the health benefits evaluation. Tables III-10 through III-13 

summarize the exposure results for these metrics. The number of person-days of exposure to 

5-hour daily maximum ozone concentrations above 90 and 100 ppb was 71 million and 

23 million in the baseline period for the SJVAB. With NAAQS attainment, the estimated 

number of person-days of exposure drops to 320 thousand and zero above 90 and 100 ppb, 

respectively. The number of person-days of exposure to 1-hour daily maximum concentrations 

above 100 and 120 ppb was 46 million and 6 million, respectively, in the baseline period and 250 

thousand and zero with attainment, respectively. Results are also presented in Table III-12 for 

exposure to the 2-week average 1-hour daily maximum concentrations, which are similar to the 

exposure results for the 5-hour daily maximum concentrations. The results suggest residents of 

Fresno County have the highest number of person-days of exposure to high 1-hour and 5-hour 

daily maximum concentrations in the SJVAB, which is consistent with the results for high 8-

hour daily maximum concentrations.

Many of the concentration-response relationships rely on the 24-hour average ozone 

values which are substantially lower than the 1-hour and 8-hour daily maxima, and do not 

receive much attention because they are not the focus of the air quality standards. In the SJVAB, 

there are an estimated 97 million person-days of exposure per year to 24-hour average ozone 

concentrations above 50 ppb. There are also 17 million and 1.7 million person-days of exposure 

to 24-hour average ozone concentrations above 60 and 70 ppb, respectively, in the 2002-2004 

baseline period. With attainment, 19 million, 650 thousand, and zero person-days of exposure to 

24-hour average ozone concentrations above 50, 60, and 70 ppb are estimated to occur in the air 

basin annually. Residents of Kern, Tulare, and Fresno Counties are estimated to have about the 

same number (4 million) of persons-days of exposure to 24-hour ozone above 60 ppb in the 

baseline period. With attainment, residents of Kern and Tulare Counties are estimated to have 

387 thousand and 198 thousand person-days above 60 ppb compared to 15 thousand person-days 

for residents of Fresno County. The relative importance of 24-hour exposures appears higher in 

the southern portion of the SJVAB. 

The results for alternate ozone exposure metrics suggest attainment of the NAAQS is 

likely to produce major reductions in all ozone metrics relevant to protection of public health, not 

just the 8-hour daily maximum exposures which are the focus of the standard. Because the 

relationships between the metrics vary between counties and between the urban-core, suburban, 
20

and rural areas within counties, the relative benefits of attainment are likely to vary with the 

metric selected for a particular evaluation.

III.5.3.3 24-hour Average PM2.5 Exposures

The estimated number of exposures of the SJVAB population to 24-hour average PM2.5

concentrations above 40 and 65 μg/m3 are shown in Tables III-14 through III-18. The results for 

the baseline period indicate about 88 million and 8.7 million person-days of exposure to 

concentrations above 40 and 65 μg/m3 occur annually in the SJVAB. The majority of the 

exposures occur in Fresno and Kern Counties. The average number of days of exposure to 

concentrations above 40 μg/m3 is 32 and 39 days per year in Fresno and Kern Counties, 

respectively, compared to 26 days per year on average in the SJVAB in 2002-2004. The 

estimated average number of days of exposure above the 65 μg/m3 level of the NAAQS ranges 

from zero in San Joaquin County to 4 per year in Fresno and Kern Counties.

With attainment of the 24-hour NAAQS, which is much less stringent than the annual 

NAAQS, SJVAB population exposure to 24-hour average PM2.5 concentrations above 40 and 

65 μg/m3 is estimated to be 61 million and 3.2 million person-days per year above 40 and 

65 μg/m3, respectively. This represents a 63% decrease in person-days of exposure above the 

level of the standard on average. On a county basis, the model estimates 36%, 38%, 73%, 86%, 

93%, 97%, 100%, and 100% fewer person-days of PM2.5 exposure above 65 μg/m3 will occur 

with attainment of the 24-hour NAAQS in Kern, Stanislaus, Fresno, Tulare, Kings, San Joaquin, 

Merced, and Madera Counties, respectively. On average, residents of Kern and Stanislaus 

Counties are likely to experience two days per year with 24-hour average PM2.5 concentrations 

above 65 μg/m3 after attainment of the 24-hour NAAQS.

Table III-17 and III-18, and Figures III-24 and III-25 show the results for estimated daily

PM2.5 exposures by racial/ethnic group. They suggest that blacks and Hispanics have slightly 

more frequent exposure to elevated PM2.5 concentrations than whites and other races in the 

SJVAB. The largest difference in racial/ethnic group PM2.5 exposure frequencies occurs in 

Madera County. 

III.5.3.4 Annual Average PM2.5 Exposures

The estimated annual average exposure of SJVAB residents to PM2.5 in the 2002-2004 

and with attainment is summarized in Tables III-19 through III-24. The exposure calculations

indicate 98%, 74%, and 33% of the SJVAB population are exposed to annual average PM2.5

concentrations above 12, 15, and 18 μg/m3. Approximately 31%, 33%, 67%, 74%, 85%, 95%, 

97%, and 98% of the residents of San Joaquin, Stanislaus, Merced, Kern, Madera, Tulare, 

Fresno, and Kings counties are exposed to annual average PM2.5 concentrations above 15 μg/m3

in the baseline period, respectively. Similarly, 77% and 72% of residents, ages less than 1 year 

and greater than 64 years, are estimated to be exposed to annual average PM2.5 concentrations 

above 15 μg/m3 in the baseline period. Approximately 70%, 71%, 77%, and 79% of white, other 

race, black, and Hispanic residents are estimated to be exposed to annual PM2.5 concentrations 

above the NAAQS threshold. 
21

With attainment of the annual NAAQS, the model estimates that 0%, 16%, and 73% of 

the SJVAB population will be exposed to annual concentrations above 12, 15, and 18 μg/m3, 

respectively. No exposures to annual PM2.5 concentrations above 15 μg/m3 are estimated to 

occur in the northern half of the SJVAB (i.e., in San Joaquin, Stanislaus, Merced, and Madera 

Counties) with attainment. However, approximately 16%, 22%, 27%, and 30% of residents in 

Kern, Fresno, Tulare, and Kings Counties, respectively, are estimated to be exposed to annual 

PM2.5 concentrations above 15 μg/m3 under the NAAQS attainment scenario. Also, the majority 

(73% to 96%) of residents of Madera, Fresno, Kings, Tulare, and Kern Counties are estimated to 

be exposed to annual PM2.5 concentrations above 12 μg/m3 with annual NAAQS attainment. 

Nevertheless, the estimated reduction of population exposed to annual PM2.5 greater than 

15 μg/m3 from 2.5 million people (74% of the population) in 2002-2004 to 520 thousand people 

(16% of the population) with NAAQS attainment represents a substantial improvement in air 

quality and a decrease in associated PM-related health effects (including premature mortality) for 

residents of the SJVAB. 
22

Table III-4. The estimated SJVAB population exposure to 8-hour daily maximum ozone 

concentrations above 70, 85, and 100 ppb in the 2002-2004 baseline period and with NAAQS 

attainment by region.

Region

Person-days of Exposure Per Year in the 

2002 – 2004 Baseline Period

Person-days of Exposure Per 

Year With NAAQS Attainmenta

O3 >70 ppb O3 >85 ppb O3 >100 ppb O3 >70 ppb O3 >85 ppb

SJV Air Basin 234,844,480 68,981,644 10,263,964 33,831,101 292,757

San Joaquin County 5,841,758 272,877 4,696 5,314 0

Stanislaus County 13,347,645 2,102,079 80,860 684,963 0

Merced County 14,889,810 4,626,388 577,332 2,480,696 362

Madera County 12,873,744 3,436,128 538,545 1,625,296 45,633

Fresno County 76,781,642 25,510,837 5,514,961 14,614,819 211,237

Kings County 10,824,809 2,567,352 301,929 1,030,735 0

Tulare County 38,564,534 10,767,642 1,071,872 4,520,114 62

Kern County 61,720,538 19,698,341 2,173,769 8,869,163 35,463

a Person-days of exposure to ozone >100 ppb is estimated to be zero with attainment of the 8-hour NAAQS.

Table III-5. The estimated average number of days per year that the SJVAB population is 

exposed to 8-hour daily maximum ozone concentrations above 70, 85, and 100 ppb 

in the 2002-2004 baseline period and with NAAQS attainment by region.

Region

Average No. of Days of Exposure Per Year in 

the 2002 – 2004 Baseline Period

Average No. of Days of 

Exposure Per YearWith 

NAAQS Attainmenta

O3 >70 ppb O3 >85 ppb O3 >100 ppb O3 >70 ppb O3 >85 ppb

SJV Air Basin 70 21 3 10 <1

San Joaquin County 10 0 0 0 0

Stanislaus County 29 5 0 1 0

Merced County 67 21 3 11 0

Madera County 81 22 3 10 <1

Fresno County 94 31 7 18 <1

Kings County 79 19 2 8 0

Tulare County 100 28 3 12 0

Kern County 106 34 4 15 <1

a Days of exposure to ozone >100 ppb is estimated to be zero with attainment of the 8-hour NAAQS.
23

Table III-6. The estimated SJVAB population exposure to 8-hour daily maximum ozone 

concentrations above 70, 85, and 100 ppb in the 2002-2004 baseline period and 

with NAAQS attainment by age group.

Age Group

Person-days of Exposure Per Year in the 

2002 – 2004 Baseline Period

Person-days of Exposure Per 

YearWith NAAQS Attainmenta

O3 >70 ppb O3 >85 ppb O3 >100 ppb O3 >70 ppb O3 >85 ppb

Children <1 Year 3,872,925 1,149,985 172,609 567,167 4,836

Children 1 Year 3,904,201 1,157,552 173,809 570,946 4,906

Children 2-4 Years 12,166,958 3,604,316 540,086 1,776,968 15,228

Children 5-17 Years 55,807,112 16,494,003 2,450,812 8,112,525 68,028

Adults 18-21 Years 14,998,006 4,434,267 671,161 2,193,130 18,836

Adults 22-29 Years 26,760,371 7,873,702 1,181,929 3,870,832 34,088

Adults 30-64 Years 94,822,090 27,664,729 4,073,571 13,487,462 119,204

Adults >64 Years 22,512,583 6,603,022 999,976 3,252,038 27,631

a Person-days of exposure to ozone >100 ppb is estimated to be zero with attainment of the 8-hour NAAQS.

Table III-7. The estimated average number of days per year that the SJVAB population is 

exposed to 8-hour daily maximum ozone concentrations above 70, 85, and 100 ppb 

in the 2002-2004 baseline period and with NAAQS attainment by age groups.

Age Group

Average No. of Days of Exposure Per Year in 

the 2002 – 2004 Baseline Period

Average No. of Days of 

Exposure Per YearWith 

NAAQS Attainmenta

O3 >70 ppb O3 >85 ppb O3 >100 ppb O3 >70 ppb O3 >85 ppb

Children <1 Year 72 22 3 11 <1

Children 1 Year 72 21 3 11 <1

Children 2-4 Years 72 21 3 10 <1

Children 5-17 Years 71 21 3 10 <1

Adults 18-21 Years 71 21 3 10 <1

Adults 22-29 Years 72 21 3 10 <1

Adults 30-64 Years 69 20 3 10 <1

Adults >64 Years 68 20 3 10 <1

a Days of exposure to ozone >100 ppb is estimated to be zero with attainment of the 8-hour NAAQS.
24

Table III-8. The estimated SJVAB population exposure to 8-hour daily maximum ozone 

concentrations above 70, 85, and 100 ppb in the 2002-2004 baseline period and 

with NAAQS attainment by racial or ethnic group.

Group

Person-days of Exposure Per Year in the 

2002 – 2004 Baseline Period

Person-days of Exposure Per 

Year With NAAQS Attainmenta

O3 >70 ppb O3 >85 ppb O3 >100 ppb O3 >70 ppb O3 >85 ppb

White 102,861,799 29,522,344 4,173,191 14,088,345 124,941

Black 10,879,697 3,206,169 472,590 1,589,282 15,431

Hispanic 106,115,459 31,818,857 4,882,668 15,876,654 128,487

Other 15,151,622 4,482,164 741,113 2,298,549 24,006

a Person-days of exposure to ozone >100 ppb is estimated to be zero with attainment of the 8-hour NAAQS.

Table III-9. The estimated average number of days per year the SJVAB population is exposed to 

8-hour daily maximum ozone concentrations above 70, 85, and 100 ppb in the 

2002-2004 baseline period and with NAAQS attainment by racial or ethnic group.

Group

Average No. of Days of Exposure Per Year in 

the 2002 – 2004 Baseline Period

Average No. of Days of 

Exposure Per YearWith 

NAAQS Attainmenta

O3 >70 ppb O3 >85 ppb O3 >100 ppb O3 >70 ppb O3 >85 ppb

White 67 19 3 9 <1

Black 68 20 3 10 <1

Hispanic 76 23 4 11 <1

Other 62 18 3 9 <1

a Days of exposure to ozone >100 ppb is estimated to be zero with attainment of the 8-hour NAAQS.
25

 

Figure III-1. Grid system used for assignment of population and air quality data in the SJVAB and gridded total population data for 

2000. 
26

Figure III-2. The frequency of ozone NAAQS exceedance days in the SJVAB from 1990 to 

2004. The figure shows the number of days per year with 8-hour daily maximum ozone 

concentrations at one or more stations above the NAAQS and the 7-year average frequency 

(from SJVAPCD 2005).

Figure III-3. The frequency and severity of ozone NAAQS exceedances in the SJVAB from 

2001 to 2004. Severity is indicated by the NAAQS exceedance percentage on the worst day of 

the year (from SJVAPCD 2005).
27

0

10

20

30

40

50

60

70

80

90

100

Stockton

Modesto

Merced

Clovis

Fresno - 1st St.

Fresno - Hamilton

Visalia

Corcoran

Bakersfield - Golden St.

Bakersfield - Calif. Ave

Bakersfield - Planz

Location

Concentration (ug/m3)

2002

2003

2004

NAAQS

0

5

10

15

20

25

Stockton

Modesto

Merced

Clovis

Fresno - 1st St.

Fresno - Hamilton

Visalia

Corcoran

Bakersfield - Golden St.

Bakersfield - Calif. Ave

Bakersfield - Planz

Location

Concentration (ug/m3) .

2002

2003

2004

NAAQS

Figure III-4. Ninety-eighth percentile 24-hour average PM2.5 concentrations (top) and annual 

average PM2.5 concentrations (bottom) at key monitoring stations in the SJVAB in 2002 – 2004.
28

 

Figure III-5. Locations of air monitoring stations for PM2.5 (left) and ozone (right) in and around the SJVAB
29

 

Figure III-6. Spatially mapped annual average PM2.5 concentrations for 2002, 2003, and 2004 in the SJVAB.
30

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

40 50 60 70 80 90 100 110 120 130 140

8-hr Daily Maximum Ozone Concentration Threshold (ppb)

Person-days per year above threshold .

2002 - 2004 Baseline

Future 8-hr NAAQS Attainment

8-hr Ozone NAAQS

Figure III-7. The distribution of persons-days per year of exposure to 8-hour daily maximum 

ozone concentrations above various concentration thresholds in 2002-2004 and 

with NAAQS attainment.

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

30 40 50 60 70 80 90 100

24-hr Average Ozone Concentration Threshold (ppb)

Person-days per year above threshold .

2002 - 2004 Baseline

Future 8-hr NAAQS Attainment

Figure III-8. The distribution of persons-days per year of exposure to 24-hour average ozone 

concentrations above various concentration thresholds in 2002-2004 and with 

NAAQS attainment.
31

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

60 70 80 90 100 110 120 130 140 150 160

1-hr Daily Maximum Ozone Concentration Threshold (ppb)

Person-days per year above threshold .

2002 - 2004 Baseline

Future 8-hr NAAQS Attainment

1-hr Ozone NAAQS

Figure III-9. The distribution of persons-days per year of exposure to 1-hour daily maximum 

ozone concentrations above various concentration thresholds in 2002-2004 and 

with NAAQS attainment.

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

60 70 80 90 100 110 120 130 140 150 160

2-Week Average 1-hr Daily Maximum Ozone Concentration Threshold (ppb)

Person-days per year above threshold .

2002 - 2004 Baseline

Future 8-hr NAAQS Attainment

Figure III-10. The distribution of persons-days per year of exposure to 2-week average 1-hour 

daily maximum ozone concentrations above various concentration thresholds in 

2002-2004 and with NAAQS attainment.
32

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

50 60 70 80 90 100 110 120 130 140 150

5-hr Daily Maximum Ozone Concentration Threshold (ppb)

Person-days per year above threshold .

2002 - 2004 Baseline

Future 8-hr NAAQS Attainment

Figure III-11. The distribution of persons-days per year of exposure to 5-hour daily maximum 

ozone concentrations above various concentration thresholds in 2002-2004 and 

with NAAQS attainment.
33

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

10 20 30 40 50 60 70 80 90

24-hr Average PM2.5 Concentration Threshold (ug/m3)

Person-days per year above threshold .

2002 - 2004 Baseline

Future 24-hr NAAQS Attainment

24-hr PM2.5 NAAQS

Figure III-12. The distribution of persons-days per year of exposure to 24-hour average PM2.5

concentrations above various concentration thresholds in 2002-2004 and with 

NAAQS attainment.

1.E+04

1.E+05

1.E+06

1.E+07

10 12 14 16 18 20 22 24 26

Annual Average PM2.5 Concentration Threshold (ug/m3)

Persons Exposed per year above threshold .

2002 - 2004 Baseline

Future Annual NAAQS Attainment

Annual PM2.5 NAAQS

Figure III-13. The distribution of persons exposed per year to annual average PM2.5

concentrations above various concentration thresholds in 2002-2004 and with the 

annual NAAQS attainment.
34

Figure III-14. Spatial map of the number of person-days per year of exposure to 8-hour daily 

maximum ozone concentrations above 100 ppb in 2002-2004.
35

 

Figure III-15. Spatial map of the number of person-days per year of exposure to 8-hour daily maximum ozone concentrations above 

85 ppb in 2002-2004 (left) and with NAAQS attainment (right).
36

 

Figure III-16. Spatial map of the number of person-days per year of exposure to 8-hour daily maximum ozone concentrations above 

70 ppb in 2002-2004 (left) and with NAAQS attainment (right).
37

 

Figure III-17. Spatial map of the number of person-days per year of exposure to 24-hour average PM2.5 concentrations above 

65 μg/m3 in 2002-2004 (left) and with 24-hour NAAQS attainment (right).
38

 

 

Figure III-18. Spatial map of the number of person-days per year of exposure to 24-hour average PM2.5 concentrations above 

40 μg/m3 in 2002-2004 (left) and with 24-hour NAAQS attainment (right). 
39

 

Figure III-19. Spatial map of the number of persons exposed (per year) to annual average PM2.5

concentrations above 18 μg/m3 in 2002-2004.
40

 

Figure III-20. Spatial map of the number of persons exposed to annual average PM2.5 concentrations above 15 μg/m3 in 2002-2004 

(left) and with attainment (right).
41

 

Figure III-21. Spatial map of the number of persons exposed to annual average PM2.5 concentrations above 12 μg/m3 in 2002-2004 

(left) and with attainment (right).
42

-

10

20

30

40

50

60

>95 ppb >90 ppb >85 ppb >80 ppb >75 ppb

Concentration Threshold

y p 

White

Black

Other

Hispanic

Total Population

Figure III-22. The average number of days per year of exposure to 8-hour daily maximum ozone 

above various concentrations in the SJVAB in 2002-2004 by racial/ethnic group 

and county.

-

5

10

15

20

25

30

35

40

San

Joaquin

County

Stanilaus

County

Merced

County

Madera

County

Fresno

County

Kings

County

Tulare

County

Kern

County

County

Days Per Year .

White

Black

Other

Hispanic

Total Population

Figure III-23. The average number of days per year of exposure to 8-hour daily maximum ozone 

above 85 ppb in the SJVAB in 2002-2004 by racial/ethnic group and county.
43

Table III-10. The estimated SJVAB population exposure to 5-hour daily maximum ozone 

concentrations above 80, 90 and 100 ppb in the 2002-2004 baseline period and 

with NAAQS attainment by region.

Region

Person-days of Exposure Per Year in the 

2002 – 2004 Baseline Period

Person-days of Exposure Per 

Year With NAAQS Attainmenta

O3 >80 ppb O3 >90 ppb O3 >100 ppb O3 >80 ppb O3 >90 ppb

SJV Air Basin 160,612,236 70,992,203 23,036,909 8,774,819 323,671

San Joaquin County 3,485,314 507,787 5,099 4,796 184

Stanislaus County 9,227,736 3,122,399 546,788 87,867 0

Merced County 10,013,959 4,521,107 1,445,128 255,225 0

Madera County 8,425,272 3,299,209 1,177,622 447,320 51,767

Fresno County 53,782,698 27,837,387 11,595,938 5,618,393 228,973

Kings County 6,594,764 2,795,412 792,613 259,751 0

Tulare County 27,267,903 11,699,739 3,085,285 1,027,820 6,769

Kern County 41,814,589 17,209,163 4,388,438 1,073,646 35,978

a SJVAB population exposure to 5-hour daily maximum ozone >100 ppb is estimated to be 6,770 person-days per year with 

attainment of the 8-hour NAAQS.

Table III-11. The estimated SJVAB population exposure to 1-hour daily maximum ozone 

concentrations above 80, 100, and 120 ppb in the 2002-2004 baseline period and 

with NAAQS attainment by region.

Region

Person-days of Exposure Per Year in the 

2002 – 2004 Baseline Period

Person-days of Exposure Per 

Year With NAAQS Attainmenta

O3 >80 ppb O3 >100 ppb O3 >120 ppb O3 >80 ppb O3 >100 ppb

SJV Air Basin 213,217,847 45,904,168 6,063,003 20,176,110 254,935

San Joaquin County 8,395,004 488,874 4,888 10,681 4,728

Stanislaus County 15,166,787 2,353,467 48,987 534,337 0

Merced County 13,345,890 2,755,607 90,682 1,052,372 105

Madera County 10,842,116 2,088,746 293,815 1,008,657 34,359

Fresno County 69,222,219 20,903,413 4,408,225 11,620,506 185,340

Kings County 9,113,833 1,692,956 179,469 664,759 0

Tulare County 34,870,509 7,110,469 576,116 2,853,119 7,173

Kern County 52,261,490 8,510,636 460,819 2,431,680 23,230

a SJVAB population exposure to 1-hour daily maximum ozone >120 ppb is estimated to be zero with attainment of the 8-hour 

NAAQS.
44

Table III-12. The estimated SJVAB population exposure to 2-week average 1-hour daily 

maximum ozone concentrations above 80, 100, and 120 ppb in the 2002-2004 

baseline period and with NAAQS attainment by region.

Region

Person-days of Exposure Per Year in the 

2002 – 2004 Baseline Period

With NAAQS 

Attainmenta

O3 >80 ppb O3 >100 ppb O3 >120 ppb O3 >80 ppb

SJV Air Basin 176,546,856 7,754,966 77,308 1,020,681

San Joaquin County 29,539 0 0 0

Stanislaus County 3,631,794 0 0 0

Merced County 10,437,480 148,280 0 0

Madera County 9,299,083 206,757 0 41,004

Fresno County 68,672,341 4,893,914 31,738 497,532

Kings County 6,769,397 48,949 0 126

Tulare County 33,531,673 1,056,492 403 110,562

Kern County 44,175,548 1,400,575 45,166 371,457

a SJVAB population exposure to 2-week average 1-hour daily maximum ozone >100 ppb is estimated to 

be zero with attainment of the 8-hour NAAQS.

Table III-13. The estimated SJVAB population exposure to 24-hour average ozone 

concentrations above 50, 60, and 70 ppb in the 2002-2004 baseline period and with NAAQS 

attainment by region.

Region

Person-days of Exposure Per Year in the 

2002 – 2004 Baseline Period

Person-days of Exposure Per 

Year With NAAQS Attainmenta

O3 >50 ppb O3 >60 ppb O3 >70 ppb O3 >50 ppb O3 >60 ppb

SJV Air Basin 97,277,322 16,992,036 1,741,620 19,462,969 653,916

San Joaquin County 319,971 787 0 6,418 0

Stanislaus County 1,867,299 44,491 79 59,409 0

Merced County 8,842,703 1,719,219 193,478 1,908,731 30,960

Madera County 7,058,729 1,478,549 137,148 1,790,058 23,539

Fresno County 35,382,682 4,695,127 76,214 4,426,329 14,643

Kings County 3,023,231 110,651 0 112,848 0

Tulare County 18,298,749 4,094,132 502,563 5,376,160 197,971

Kern County 22,483,957 4,849,080 832,139 5,783,017 386,803

a SJVAB population exposure to 24-hour average ozone >70 ppb is estimated to be 32,000 person-days per year with attainment 

of the 8-hour NAAQS.
45

Table III-14. The estimated SJVAB population exposure to 24-hour average PM2.5

concentrations above 40 and 65 μg/m3 in the 2002-2004 baseline period and with

NAAQS attainment by region.

Region

Person-days of Exposure Per Year in 

the 2002 – 2004 Baseline Period

Person-days of Exposure Per Year

With NAAQS Attainment

PM2.5 >40 μg/m3 PM2.5 >65 μg/m3 PM2.5 >40 μg/m3 PM2.5 >65 μg/m3

SJV Air Basin 88,444,759 8,740,819 61,210,349 3,244,681

San Joaquin County 6,952,506 179,520 3,128,221 6,152

Stanislaus County 10,598,815 1,319,551 6,330,681 816,627

Merced County 4,517,016 337,293 2,602,691 1,509

Madera County 4,176,348 159,435 2,512,053 0

Fresno County 25,612,174 3,536,683 19,033,269 961,833

Kings County 3,704,890 415,924 2,909,207 27,889

Tulare County 9,857,985 724,773 7,308,016 102,482

Kern County 23,025,025 2,067,641 17,386,210 1,328,188

Table III-15. The estimated average number of days per year that the SJVAB population is 

exposed to 24-hour PM2.5 concentrations above 40 and 65 μg/m3 in the 2002-2004 

baseline period and with NAAQS attainment by region.

Region

Average No. of Days of Exposure Per 

Year in the 2002 – 2004 Baseline Period

Average No. of Days of Exposure 

Per YearWith NAAQS Attainment

PM2.5 >40 μg/m3 PM2.5 >65 μg/m3 PM2.5 >40 μg/m3 PM2.5 >65 μg/m3

SJV Air Basin 26 3 18 1

San Joaquin County 12 0 5 <1

Stanislaus County 23 3 14 2

Merced County 20 2 12 <1

Madera County 26 1 16 0

Fresno County 32 4 23 1

Kings County 27 3 21 <1

Tulare County 26 2 19 <1

Kern County 39 4 30 2
46

Table III-16. The estimated SJVAB population exposure to 24-hour average PM2.5

concentrations above 40 and 65 μg/m3 in the 2002-2004 baseline period and with

NAAQS attainment by age group.

Age Group

Person-days of Exposure Per Year in 

the 2002 – 2004 Baseline Period

Person-days of Exposure Per Year

With NAAQS Attainment

PM2.5 >40 μg/m3 PM2.5 >65 μg/m3 PM2.5 >40 μg/m3 PM2.5 >65 μg/m3

Children <1 Year 1,451,170 145,336 1,014,127 53,513

Children 1 Year 1,469,069 146,894 1,024,404 54,377

Children 2-4 Years 4,573,955 457,019 3,184,968 168,053

Children 5-17 Years 20,902,138 2,073,829 14,525,114 761,301

Adults 18-21 Years 5,634,636 556,778 3,910,283 206,015

Adults 22-29 Years 10,110,743 1,002,256 7,031,299 373,369

Adults 30-64 Years 35,816,787 3,503,922 24,685,357 1,313,479

Adults >64 Years 8,486,261 854,785 5,834,797 314,575

Table III-17. The estimated SJVAB population exposure to 24-hour average PM2.5

concentrations above 40 and 65 μg/m3 in the 2002-2004 baseline period and with 

NAAQS attainment by racial or ethnic group.

Group

Person-days of Exposure Per Year in 

the 2002 – 2004 Baseline Period

Person-days of Exposure Per Year

With NAAQS Attainment

PM2.5 >40 μg/m3 PM2.5 >65 μg/m3 PM2.5 >40 μg/m3 PM2.5 >65 μg/m3

White 39,421,625 3,842,572 26,815,582 1,558,292

Black 4,439,192 486,888 3,128,836 163,693

Other 38,467,115 3,771,060 27,133,707 1,300,489

Hispanic 6,158,795 643,435 4,160,633 223,028

Table III-18. The estimated average number of days per year that the SJVAB population is 

exposed to 24-hour PM2.5 concentrations above 40 and 65 μg/m3 in the 2002-2004 

baseline period and with NAAQS attainment by racial or ethnic group.

Group

Average No. of Days of Exposure Per 

Year in the 2002 – 2004 Baseline Period

Average No. of Days of Exposure 

Per YearWith NAAQS Attainmenta

PM2.5 >40 μg/m3 PM2.5 >65 μg/m3 PM2.5 >40 μg/m3 PM2.5 >65 μg/m3

White 26 2 17 1

Black 28 3 20 1

Hispanic 28 3 19 1

Other 25 3 17 1
47

0

10

20

30

40

50

60

65 ug/m3 50 ug/m3 40 ug/m3 30 ug/m3

Concentration Threshold

Days Per Year 

White

Black

Other

Hispanic

Total Population

Figure III-24. The average number of days per year of exposure to 24-hour average PM2.5 above 

various concentrations in the SJVAB in 2002-2004 by racial/ethnic group.

0

5

10

15

20

25

30

35

40

45

San

Joaquin

County

Stanilaus

County

Merced

County

Madera

County

Fresno

County

Kings

County

Tulare

County

Kern

County

Days Per Year 

White

Black

Other

Hispanic

Total Population

Figure III-25. The average number of days per year of exposure to 24-hour average PM2.5 above 

40 μg/m3 in the SJVAB in 2002-2004 by racial/ethnic group and county.
48

Table III-19. The estimated SJVAB population exposure to annual average PM2.5 concentrations 

above 12, 15, and 18 μg/m3 in the 2002-2004 baseline period and with NAAQS 

attainment by region.

Region

Person-days of Exposure Per Year in the 

2002 – 2004 Baseline Period

Person-days of Exposure Per 

Year With NAAQS Attainmenta

PM2.5 >12 

μg/m3

PM2.5 >15 

μg/m3

PM2.5 >18 

μg/m3

PM2.5 >12 

μg/m3

PM2.5 >15 

μg/m3

SJV Air Basin 3,266,891 2,485,816 1,110,165 2,429,546 520,575

San Joaquin County 548,259 180,226 733 179,474 0

Stanislaus County 465,500 155,140 140,181 155,101 0

Merced County 209,607 148,200 55,780 107,450 0

Madera County 139,758 135,335 44,189 134,303 0

Fresno County 802,163 784,847 214,722 783,162 182,782

Kings County 137,234 134,433 45,745 130,317 41,082

Tulare County 380,256 363,833 156,907 356,090 102,345

Kern County 584,114 583,802 451,908 583,649 194,366

a

 None of the SJVAB population is estimated to be exposed to annual average PM2.5 concentrations above >18 μg/m3 with 

attainment of the annual PM2.5 NAAQS.

Table III-20. The estimated percent of the SJVAB population exposed to annual average PM2.5

concentrations above 12, 15, and 18 μg/m3 in the 2002-2004 baseline period and 

with NAAQS attainment by region.

Region

Percent of the Population Exposed in the 

2002 – 2004 Baseline Period

Percent of the Population 

Exposed With NAAQS 

Attainmenta

PM2.5 >12 

μg/m3

PM2.5 >15 

μg/m3

PM2.5 >18 

μg/m3

PM2.5 >12

μg/m3

PM2.5 >15 

μg/m3

SJV Air Basin 98% 74% 33% 73% 16%

San Joaquin County 96% 31% 0% 31% 0%

Stanislaus County 100% 33% 30% 33% 0%

Merced County 94% 67% 25% 48% 0%

Madera County 88% 85% 28% 84% 0%

Fresno County 99% 97% 26% 96% 22%

Kings County 100% 98% 33% 95% 30%

Tulare County 99% 95% 41% 93% 27%

Kern County 98% 74% 33% 73% 16%

a None of the SJVAB population is estimated to be exposed to annual average PM2.5 concentrations above >18 μg/m3 with 

attainment of the annual PM2.5 NAAQS.
49

Table III-21. The estimated SJVAB population exposure to annual average PM2.5 concentrations 

above 12, 15, and 18 μg/m3 in the 2002-2004 baseline period and with NAAQS 

attainment by age group.

Age Group

Person-days of Exposure Per Year in the 

2002 – 2004 Baseline Period

Person-days of Exposure Per 

YearWith NAAQS Attainmenta

PM2.5 >12 

μg/m3

PM2.5 >15 

μg/m3

PM2.5 >18 

μg/m3

PM2.5 >12 

μg/m3

PM2.5 >15 

μg/m3

Children <1 Year 52,518 40,905 18,534 40,018 8,969

Children 1 Year 53,244 41,327 18,703 40,421 8,959

Children 2-4 Years 166,507 128,722 58,015 125,823 27,787

Children 5-17 Years 767,767 588,313 264,331 574,640 125,186

Adults 18-21 Years 206,777 159,584 70,214 155,994 33,718

Adults 22-29 Years 367,444 285,834 127,762 279,426 61,316

Adults 30-64 Years 1,332,637 1,005,231 448,785 982,455 205,947

Adults >64 Years 319,994 235,898 103,822 230,767 48,692

a Zero percent of the SJVAB population is estimated to be exposed to annual average PM2.5 concentrations above >18 μg/m3

with attainment of the annual PM2.5 NAAQS.

Table III-22. The percent of the SJVAB population exposed to annual average PM2.5

concentrations above 12, 15, and 18 μg/m3 in the 2002-2004 baseline period and 

with NAAQS attainment by age group.

Age Group

Percent of the Population Exposed in the 

2002 – 2004 Baseline Period

Percent of the Population 

Exposed With NAAQS 

Attainmenta

PM2.5 >12 

μg/m3

PM2.5 >15 

μg/m3

PM2.5 >18 

μg/m3

PM2.5 >12 

μg/m3

PM2.5 >15 

μg/m3

Children <1 Year 98% 77% 35% 75% 17%

Children 1 Year 98% 76% 35% 75% 17%

Children 2-4 Years 98% 76% 34% 74% 16%

Children 5-17 Years 98% 75% 34% 73% 16%

Adults 18-21 Years 98% 76% 33% 74% 16%

Adults 22-29 Years 98% 77% 34% 75% 16%

Adults 30-64 Years 98% 74% 33% 72% 15%

Adults >64 Years 97% 72% 32% 70% 15%

a Zero percent of the SJVAB population is estimated to be exposed to annual average PM2.5 concentrations above >18 μg/m3

with attainment of the annual PM2.5 NAAQS.
50

Table III-23. The estimated SJVAB population exposure to annual average PM2.5

concentrations above 12, 15 and 18 μg/m3 in the 2002-2004 baseline period and 

with NAAQS attainment by racial or ethnic group.

Group

Person-days of Exposure Per Year in the 

2002 – 2004 Baseline Period

Person-days of Exposure Per 

Year With NAAQS Attainmenta

PM2.5 >12 

μg/m3

PM2.5 >15

μg/m3

PM2.5 >18 

μg/m3

PM2.5 >12 

μg/m3

PM2.5 >15 

μg/m3

White 1,495,318 1,085,149 496,585 1,062,947 208,770

Black 157,070 122,784 51,819 120,417 28,525

Hispanic 1,373,857 1,105,462 498,035 1,078,506 250,913

Other 242,304 173,721 64,248 168,918 32,672

a None of the SJVAB population is estimated to be exposed to annual average PM2.5 concentrations above >18 μg/m3 with 

attainment of the annual PM2.5 NAAQS.

Table III-24. The estimated percent of the SJVAB population exposed to annual average PM2.5

concentrations above 12, 15, and 18 μg/m3 in the 2002-2004 baseline period and 

with NAAQS attainment by racial or ethnic group.

Group

Percent of the Population Exposed in the 

2002 – 2004 Baseline Period

Percent of the Population Exposed 

With NAAQS Attainmenta

PM2.5 >12 

μg/m3

PM2.5 >15 

μg/m3

PM2.5 >18 

μg/m3

PM2.5 >12 

μg/m3

PM2.5 >15 

μg/m3

White 97% 70% 32% 69% 14%

Black 99% 77% 33% 76% 18%

Hispanic 99% 79% 36% 77% 18%

Other 98% 71% 26% 69% 13%

All Groups 98% 74% 33% 73% 16%

a None of the SJVAB population is estimated to be exposed to annual average PM2.5 concentrations above >18 μg/m3 with 

attainment of the annual PM2.5 NAAQS.
51

IV. ADVERSE OZONE AND PM-RELATED HEALTH EFFECTS

Ozone and fine particles (PM2.5) have long been associated with adverse health effects, 

and a growing body of health science literature enables us to quantify how changes in air quality 

translate into changes in the number of adverse health effects in a population. In order to select 

specific studies to estimate such changes for the purposes of this study, we consider a number of 

factors. In particular, to be used a study:

• Must be peer-reviewed.

• Must account for potential confounders such as other pollutants and weather.

• Must use reasonable measures of pollutants.

• Must be based on a population not significantly different from the population being 

assessed.

• Must provide a basis to estimate changes in an effect that can be valued in economic 

terms.

• Is preferred if it is more recent, using more advanced analytical methods and reflecting 

more recent demographics.

• Is preferred if it covers longer periods and larger populations.

• Is preferred if it meets other criteria and is also region-specific.

• Is preferred if it meets other criteria and has been used in previous peer-reviewed benefits 

assessments.

Given this, we identified seven ozone-related and 14 PM2.5-related effects that would be 

appropriate for inclusion in this study.3 These effects are summarized in Table IV-1. Those that 

are quantified here are shaded in gray. Those that are not quantified occur in very small numbers, 

generally because the population at risk is small or because the concentration-response 

relationship requires a large change in pollution levels to generate substantial reductions in the 

effect in the exposed population. For example, we estimate that attaining the NAAQS for PM2.5 

would result in five fewer cardiovascular hospital admissions annually in the entire eight county 

region. Summing and including all of those small effects does not change the overall results.

IV. 1 Studies Used in Quantification of Effects

IV.1.1 Developing Health (Concentration-Response) Functions 

To quantify the expected changes in health effects associated with reduced exposure to 

ozone and PM2.5, we have used the basic exponential concentration-response (C-R) function 

developed in the Environmental Protection Agency’s Report to Congress (EPA 1999), which 

evaluates the benefits and costs of emissions controls required by the Clean Air Act.4

 

 3 Some effects, such as individual respiratory symptoms or eye irritation are not included here because they are at 

least in part captured by effects such as MRADs, work loss days, school absence days and upper and lower 

respiratory symptom days. Also, individually they carry relatively small economic values.

4 The one exception is the case of ozone-related emergency room visits, for which we use a linear concentrationresponse function.
52

Specifically, the functional form used is as follows:

∆ C = -C0(e-β∆P – 1)

where:

∆C = the change in the number of cases (of a particular health outcome)

C0 = the number of baseline cases (of the health outcome)

∆P = the change in ambient pollution concentrations

β = an exponential “slope” factor derived from the health literature

 pertaining to that specific health outcome.

In most of the recent health literature, “relative risk” factors are reported which relate change in 

pollution levels to the increased odds of developing various health effects. These risk factors are 

related to the β in the EPA concentration-response functions in the following manner:

β = (1 + Increased Odds)/(Change in Pollution)

The specific health studies used to develop these β values are described in the following sections.

IV.1.2 Ozone Morbidity

Minor Restricted Activity Days (MRADs)

Minor restricted activity days (MRADs) are days when various (often, respiratory) 

symptoms reduce normal activities, but do not prevent going to work or attending school. The 

combination of symptoms that induces an MRAD is more restrictive than any individual 

symptom. The 1989 study by Ostro and Rothschild, which used a national sample of the adult 

(18-65) working population over six years (1976-1981) to determine some of the health 

consequences of ozone and fine particles, is used here. They found an association between 

ozone and minor restrictions in activity, after controlling for fine particles, that can be used to 

derive an exponential ozone C-R function. Using a weighted average of the coefficients reported 

in the analysis, the EPA (2003b) developed a best estimate β coefficient of 0.0022; an annual 

(baseline) number of 7.8 MRADs per person was also derived from the study. Further following 

Ostro and Rothschild, we apply this function to the nonelderly, or “working” adult portion of the 

population. The EPA (2003b) notes that this application is likely to produce a somewhat 

conservative health outcome estimate, since elderly adults are probably at least as susceptible to 

ozone pollution as are individuals under the age of 65.

Asthma Emergency Room Visits

Several studies have established a relationship between increases of ozone and a variety 

of asthmatic symptoms. In one of the more comprehensive works undertaken, Weisel et al. 

(1995) conducted a five-year retrospective study of the relationship between summer ozone 

concentrations and asthma-induced emergency room (ER) visits. Specifically, they examined 

the relationship between ambient ozone levels and ER visits by asthmatics in central and 

northern New Jersey for five consecutive years (1986 - 1990). A similar study was undertaken 

by Cody et al. (1992) for the same geographic area and the summer months of 1988 and 1989. 

While Weisel et al.’s results derive from a single pollutant equation, the Cody et al. study 
53

includes SO2 as a co-pollutant. In each case, though, multiple linear regression analyses were 

conducted for each year, generating positive and significant coefficients of daily ER visits with 

ozone concentrations. From these studies’ coefficients, the EPA (2003b) derives slope 

coefficients for a linear concentration-response function. For our analysis, we average these two 

linear coefficients, resulting in a β value of 0.0323. It is this value that forms the basis for our 

calculation of reductions in asthma-related emergency room visits from improved ozone levels. 

The specific function thus developed is as follows:

Δ asthma-related ER visits = (β/ Base Pop) ΔO3 pop,

where: β = ozone coefficient = 0.0323

Base Pop = original studies’ baseline population in NJ = 4,436,976

Δ O3 = change in daily 5-hour average ozone concentration (ppb)

pop = the affected population (all ages).

School Absences

Ozone-related school absences is a health outcome that has been examined in two 

recently published health studies. The first, by Chen et al. (2000), considered the association 

between air pollution and daily elementary school absenteeism in Washoe County, Nevada, from 

1996 to 1998. Student absenteeism was regressed on three air pollutants (ozone, PM10 and 

carbon monoxide), weather variables, and other confounding factors, using autoregression 

analysis. The second study, by Gilliland et al. (2001), examined 1996 school absences for 12 

southern California communities with differing concentrations of multiple pollutants (ozone, 

NO2, and carbon monoxide). These researchers used a two-stage time series regression model, 

controlling for day of the week and temperature, to assess whether there were any associations 

between pollution levels and absences. Both studies found ozone to be statistically associated 

with daily absenteeism. More specifically, Chen et al. predicted that for every 50 ppb increase in 

ozone the overall absence rate increased by 13.01 percent. In contrast, Gilliland et al. found that 

a 20 ppb increase in 8-hour average ozone concentrations was associated with a 16.3 percent 

increase in the all-absence rate. From these results, we can derive exponential β values of 

0.002446 and 0.00755, which we then average, resulting in an ozone-related school absence 

concentration-response β value of 0.004998. Finally, EPA (2003b) reports a daily school 

absence rate of 0.055, obtained from the U.S. Department of Education.

Asthma Attacks

In an early, yet still widely cited, study, Whittemore and Korn (1980) examined daily 

asthma attack diaries from 16 panels of asthmatics living in six communities of southern 

California during the mid 1970s. They used multiple logistic regression analysis to test for 

relationships between daily attack occurrences and daily levels of two types of pollutants 

(photochemical oxidants and total suspended particulates), plus a variety of weather variables. 

Results for the two pollutant models showed significant relationships between daily levels of 

both pollutants and reported asthma attacks. The EPA (2003b) adjusted the model’s oxidant 

results so that they could be used with ozone data. The resulting β value of 0.001843 can then be 

applied to the asthmatic portion of the Central Valley population, which we assume to be 3.86 

percent of the all-age population (as reported in American Lung Association 2002). Finally, a 
54

daily incidence rate of wheezing attacks for adult asthmatics of 0.055 is assumed as our baseline 

rate, based on an analysis of the 1999 National Health Interview Survey (EPA 2003b).

Respiratory Hospital Admissions 

For non-elderly (ages 0 – 64), ozone-related respiratory hospital admissions, we turn to a 

report by Thurston and Ito (1999), which summarized an extensive literature on hospital 

admissions that included ozone as one of the explanatory variables5. In this report, a statistical 

synthesis of three Canadian studies (Burnett et al. 1994, Thurston et al. 1994 and Burnett et al. 

1997a) yielded a quantitative estimate of the respiratory hospital admission effect associated with 

ozone exposures for the non-elderly general population. Specifically, they calculate a relative 

risk factor of 1.18 per 100 ppb increase in daily 1-hour maximum ozone levels. From this, we 

derive a concentration-response β estimate of 0.001655. For respiratory hospital baseline 

admission rates, we turn to the Office of Statewide Health Planning and Development’s Inpatient 

Hospital Discharge Frequencies for California (2003) and the U.S. National Hospital Discharge 

Survey (March 2005) to construct age-specific hospital discharge numbers for each county.

To estimate ozone-related avoided incidences of respiratory hospital admissions for 

patients 65 and older, we generated a pooled β value using several health studies referenced by 

the EPA (2003b). All of these studies found significant associations between ozone and various 

categories of respiratory hospital admissions. The studies include: Schwartz (1995), who 

analyzed the relationship between ozone and all respiratory admissions for the cities of New 

Haven, Connecticut and Tacoma, Washington; and Moolgavkar et al. (1997), Schwartz (1994a), 

and Schwartz (1994b), who considered pneumonia and COPD admissions in Minneapolis and 

Detroit. Our pooled β estimate is equal to 0.004536. Finally, as described for the under-65 case, 

our county-specific baseline figures come from the California and U.S. Hospital Discharge 

reports. 

IV.1.3 PM2.5 Morbidity

Chronic Bronchitis

A case of chronic bronchitis is typically considered to be a recurring condition of mucus 

in the lungs and wet cough during at least 3 months per year for several years in a row. Abbey et 

al. (1995) studied the association between fine particles (including PM2.5) and new occurrences 

of these chronic respiratory symptoms in a survey group of nearly 1,900 Californian Seventh 

Day Adventists. The survey period extended from 1977 to 1987, and the study found a 

statistically significant relationship between PM2.5 and the development of chronic bronchitis in 

adults aged 27 and over. From this work, the EPA calculated a concentration-response β value 

of 0.0137 and from an earlier work by Abbey (1993), they obtained an annual bronchitis 

incidence rate per person of 0.00378. We apply these factors to the proportion of our adult 

population (27 years of age and older) without chronic bronchitis (which, according to the 

American Lung Association, is 95.57 percent of the population).

 5 This is the same approach adopted by ARB (2005).
55

Minor Restricted Activity Days (MRADs)

As noted above in the ozone morbidity section, minor restricted activity days (MRADs) 

are days when various (often, respiratory) symptoms reduce normal activities, but do not prevent 

going to work or attending school. The 1989 study by Ostro and Rothschild noted above used 

six years (1976-1981) of Health Interview Survey (HIS) data, a large cross-sectional database 

collected by the National Center for Health Statistics, to determine some of the health 

consequences of particulate matter and ozone. They also found a statistical association between 

fine particles and minor restrictions in activity, after controlling for ozone, that can be used to 

derive an exponential PM2.5 C-R function. From the data included in the analysis, the EPA 

(2003b) developed a PM2.5 β coefficient of 0.00741, which is again a weighted average of the 

coefficients reported in Ostro and Rothschild. As in the ozone case, an annual (baseline) number 

of 7.8 MRADs per person was derived. Finally, we again apply this function to the non-elderly, 

or “working” adult portion of the population. As we noted earlier, this application is likely to 

produce a somewhat conservative health outcome estimate, since elderly adults are probably at 

least as susceptible to fine particles as are individuals under the age of 65.

Work Loss Days (WLDs)

In a 1987 study, Ostro examined the effect of fine particulate matter on work loss days 

(WLDs) using a national survey of working adults (aged 18-64) in 49 different metropolitan 

areas in the United States. He found a significant link between PM2.5 and missed days of work 

for each of the six years of the study (1976-1981), estimating separate coefficients for each year 

of the analysis. The β coefficient developed by the EPA (2003b) from this work (0.0046) is a 

weighted average of the coefficients estimated by Ostro, using the inverse of the variance as the 

weight. In addition, the EPA used a more recent data set (Adams et al. 1999) to determine a 

daily WLD incidence (baseline) rate of 0.00595, which we use in our analysis. 

Acute Bronchitis

Dockery et al. (1996) examined the respiratory health effects of exposure to a number of 

pollutants, including fine particles, on a sample of over 13,000 children (8-12 years old) from 24 

communities in the United States and Canada. Using a two-stage logistic regression model, and 

adjusting for the potential confounding effects of sex, parental asthma and education, history of 

allergies, and current smoking in the home, they found PM2.1 to be significantly related to cases 

of bronchitis. From this work, the EPA developed a PM2.5 concentration-response function for 

acute bronchitis in children. The estimated β value of 0.0272 results from combining Dockery et 

al.’s odds ratio of 1.50 with the study’s observed change in particles of 14.9 μg/m3. In addition, 

the EPA recommends using a baseline incidence rate of 0.043 cases per child per year, as 

reported by the American Lung Association (2002). Finally, while the Dockery et al. sample 

focused on children within a 5-year age range, we extend their results to include all school-aged

children, based on the assumption that the response of all school-aged children will be similar to 

those in the study’s more age group.

Lower Respiratory Symptoms

In an earlier health study, Schwartz et al. (1994) used logistic regression and found a 

statistical association between lower respiratory symptoms (defined as cough, chest pain, phlegm 
56

and wheeze) in children and a number of pollutants, including PM10, acid aerosols, gaseous 

pollutants, and fine particles. The study was conducted in six cities over a five-year period 

(1984-1988) and considered a sample of over 1,800 students enrolled in grades two through five. 

More recently, Schwartz and Neas (2000) replicated the earlier analysis, focusing their efforts on 

PM2.5. In a model that also included coarser particulate matter (PM10-2.5), an odds ratio of 1.29 

was associated with a 15 μg/m3 change in PM2.5. From this work, we generate an exposureresponse function, with an estimated β value of 0.01698 and a daily baseline rate of 0.0012. 

Finally, while the Schwartz and Neas work is suggestive of an age range from 7 to 14, we again 

extend these results to include all school-aged children because the response of older teenagers 

and younger children is likely to be similar to the children in the studied cohort.

Upper Respiratory Symptoms

In a study of Utah school children (ranging in age from 9 to 11), Pope et al. (1991) 

examined the association between daily occurrences of upper respiratory symptoms and daily 

PM10 concentrations. A day of upper respiratory symptoms was defined as consisting of one or 

more of the following symptoms: runny or stuffy nose; wet cough; and burning, aching, or red 

eyes. Using logistic regression, the study found that PM10 was significantly associated with 

upper respiratory symptoms. The EPA (2003b) used this work to develop a concentrationresponse function with a β estimate of 0.0036. We convert this PM10-derived β value to its PM2.5

counterpart (0.0072) and also rely on Pope et al.’s daily upper respiratory symptom incidence 

rate per child of 0.3419. Finally, we note that the sample size in the Pope et al. study was quite 

small, and is most representative of the asthmatic children’s population, not the total school-aged 

population. We therefore apply this exposure-response function only to asthmatic children, who 

are assumed to represent 11 percent of the total children’s population in the San Joaquin Valley. 

IV.1.4 PM2.5 Mortality

The scientific literature that assesses associations between PM2.5 and premature mortality 

in adults has expanded rapidly over the past decade, with several large scale multi-city studies 

that extend or reanalyze earlier studies (for example, Pope et al. 1995; Krewski et al. 2000; Pope 

et al. 2002) as well as a California-specific study that focuses on the Los Angles basin (Jerrett et 

al. 2005). To estimate PM2.5 - related mortality for the SJV requires determining which of these 

studies is most appropriate for conditions in this region. In general, as noted above, studies are 

preferred that: are peer reviewed, cover longer periods, are more recent (better reflecting current 

demographics and lifestyles), include larger samples, account for confounding factors, and were 

conducted in locations that have the greatest similarity to the study population. There is also an 

increasing literature that measures (Woodruff et al. 1997) or indicates the probability of (Loomis 

et al. 1999; Pereira et al. 1998; Wang et al. 1997; Chay and Greenstone 2003) an association 

between PM2.5 and mortality in children less than one year of age.

Both EPA and ARB have conducted recent benefit assessments for PM2.5 reduction (EPA 

2003; EPA 2004; EPA 2005; ARB 2005), and these assessments have also undergone peerreview of the analytical approaches used, including the choice of C-R functions. The consensus 

is that for national studies Pope et al. (2002) is the preferred basis to estimate adult mortality. 

The EPA Science Advisory Board Health Effects Committee (SAB-HEES) (2004) further 

recommends that neonatal mortality now be included in the base analysis using the C-R function 
57

from Woodruff et al. (1997). For California, there is agreement that Pope et al. provides the best 

C-R function from the national literature, but there is also agreement that Jerrett et al. (2005) 

likely better represents California (ARB 2005 and peer-review comments thereon). Following 

the professional consensus, and based on the reasons discussed below, we rely on these three 

studies to estimate mortality effects. We use Pope et al. for the primary analysis, Jerrett et al. as 

a sensitivity test for adult mortality, and Woodruff et al. as an indicator of neonatal mortality, but 

outside the primary analysis and aggregate results.

Pope et al. (2002)

This study meets all of the essential criteria noted above for the choice of a C-R function. 

It is a large-scale, longitudinal cohort study that follows a large nationally representative 

population (ages 30 and older) across 61 cities over a 16 year follow-up period from a base of 

1979-1983. Extending the follow-up period to 16 years increases the mortality data set by a 

factor of three compared to earlier studies. This study also includes PM2.5 measurements from 

1999 and the first three quarters of 2000, and controls more closely for a series of personal risk 

factors, including lifestyle and occupation. The increase for the all-cause mortality associated 

with annual average PM2.5 is 6% per 10 μg/m3.

Woodruff et al. (1997)

This is the first comprehensive national study to assess the impact of fine particles (PM10) 

on infant mortality in the United States. It includes a sample size of four million infants less than 

one year of age across 86 metropolitan areas for the interval 1989-1991. Overall, the study 

estimates an increase of 4% for all-cause infant mortality for every 10 μg/m3 increase in PM10 . 

The EPA SAB-HEES (2004) now recommends that neonatal mortality be included in primary 

benefit analyses conducted by EPA, and that the Woodruff et al. C-R be used. The Woodruff 

study, however, did not include infants in a number of states, including California (because 

maternal education levels were not reported for California). While the study is likely 

representative of national conditions, it is impossible to determine whether the omission of 

California infants makes it less representative of the California population. Consequently, for 

the purposes of this study we do not include post neonatal deaths in the primary benefit analysis.

Jerrett et al. (2005)

This study is based on the Los Angeles area population subset from the national cohort 

included in Pope et al. (2002), accounts for the same confounders, and also assesses the 

association between average annual PM2.5 and differences in mortality in the age 30 and older 

population. The authors find a substantially higher association between PM2.5 and mortality, 

with a 17% increase in all-cause mortality for every 10 μg/m3 increase in PM2.5 . While this is 

quite a large difference, contrasted with the 6% increase found by Pope et al. for the overall 

national population, there are sound reasons to conclude that the results better represent the Los 

Angeles Basin population. A primary reason is that Jerrett et al. use a detailed intraurban 

exposure measure supported by 23 PM2.5 monitors across the region. This contrasts with the 

national cohort studies that compare interurban exposure and have much less spatial resolution. 

Another is that traffic-generated primary particles have a greater association with observed 

effects, and traffic in the Los Angeles basin accounts for nearly five times the proportion of total 

primary particles emitted as in the rest of the United States, at 3.7% compared to 0.75%.
58

For purposes of assessing benefits in the SJV, the Jerrett et al. work is more appropriate 

than Pope et al. in that the exposure measure more closely fits the approach that we use in 

REHEX. However, because it is specific to the Los Angeles area population and the profile of 

traffic-related PM emissions in that region, we take the more conservative approach of relying on 

Pope et al. for our primary assessment and provide estimates based on Jerrett et al. as a 

sensitivity test. This is also the approach recommended by a peer-review group recently asked 

by ARB to consider the use of the Jerrett et al. result for a regulatory analysis (ARB 2005;

Appendix A).

IV. 2 Estimates of Reduced Adverse Health Effects with Attainment of the NAAQS

Reductions in the numbers of adverse effects vary with the degree to which the baseline 

period pollution levels exceed the standards, the size of the population at risk, and the size of the 

association between a change in pollution and triggering the effect. A further factor is the age of 

the population included in the underlying health science study. So, for example, while it is 

reasonable to think that chronic bronchitis might be caused by PM2.5 exposure in the population 

under age 27, the study that we rely on only includes ages 27 and older, so the large population 

of those under that age is treated as if this effect could not occur in that group. The same is true 

for PM2.5 -related mortality, where the population under age 30 is not included in the number of 

estimated annual deaths. Also, premature mortality, with a small risk factor, will not be as 

frequent an effect as one such as school absences, which carries a larger risk.

The number of pollution-related effects that would be avoided if the NAAQS of ozone 

and PM2.5 were met are discussed and summarized below. The economic benefit and the 

aggregate value of reducing these effects are discussed in Section V.5 below.

IV. 2.1 Reductions in Ozone-Related Effects

The reductions in effects that would be expected with attainment of the ozone NAAQS 

are shown in Table IV-2. Typically, there are fewer of the more severe effects and fewer effects 

in smaller groups (for example, the population age 65 and older). However, while there are 

relatively few reductions in ozone-related hospital admissions, at 260 per year, this is an effect 

with considerable impacts on patients and their families. The relatively larger numbers of days 

of avoided school absences, 188,000, reflects the larger population and the sensitivity of children 

to ozone. For the age 5-17 population of 783,740 this suggests that on average one in four 

children experiences a day of absence each year due to elevated ozone levels.

IV.2.2 Reductions in PM2.5 - Related Effects

PM2.5 - related effects are shown in Table IV-3. The most serious consequences of 

exposure to fine particles over the health-based standards are associated with PM2.5, and this is 

reflected in the estimated gain of nearly 500 deaths averted each year. To put this in perspective, 

we estimate that 130 people die earlier than they would each year in Fresno County. In 2001-

2003 an average of more than 180 people died in that county in motor vehicle accidents (DHS 

2005). This means that reducing pollution can account for the equivalent of avoiding two thirds 

of the motor vehicle deaths there, similar to the proportions in Kern and Stanislaus Counties. 

This illustrates the real consequences of elevated fine particle levels, and the substantial gains 
59

from attaining the NAAQS. The contribution of PM2.5 exposure to premature mortality, relative 

to reported motor vehicle deaths, is shown by county in Table IV- 4 below. 

The avoidance of chronic bronchitis, an illness that can significantly limit activity, is also 

noteworthy at 325 cases a year. Asthmatic children also avoid more than 16,000 additional days 

of upper respiratory symptoms (in addition to ozone-related school absences and asthma attacks). 

Children also experience fewer cases of acute bronchitis.

The economic value and aggregate benefits of avoiding these effects by attaining the 

NAAQS is discussed in Section V below.
60

Table IV-1 Health endpoints

Ozone PM2.5

School absences

Ages 5-17

Acute bronchitis

Ages 5-17

Emergency room visits

All ages

Lower respiratory symptoms in children

Ages 5-17

Respiratory hospital admissions

Under age 65

Upper respiratory symptoms in children

Ages 5-17 asthmatic population

Respiratory hospital admissions

Ages 65 and older

Respiratory hospital admissions

Ages 65 and older

Asthma hospital admissions

All ages of the asthmatic population

Premature death (mortality

Ages 18-64

Asthma attacks

All ages of the asthmatic population

Asthma ER visits

Under age 18

Premature death (mortality)

All ages

Minor restricted activity days

All ages

Minor restricted activity days

Ages 18-64

Onset of chronic bronchitis

Ages 27 and older

Non-fatal heart attacks

Ages 18 and older

Cardiovascular hospital admissions

Ages 18 and older

Neo-natal mortality

Under age 1

Asthma emergency room visits

Under age 18 asthmatic population

Work loss days

Ages 18-64

Asthma hospital admissions

Ages 64 and under
61

Table IV-2 Ozone-Related Effects

Fresno Kern Kings Madera Merced San 

Joaquin

Stanislaus Tulare Total

Respiratory Hospital 

Admissions

Ages 0-64

55 45 10 10 10 15 20 30 195

Respiratory Hospital 

Admissions

Ages 65+

25 15 0 5 5 0 5 10 65

Respiratory Hospital 

Admissions

All ages

80 60 10 15 15 15 25 40 260

Asthma Attacks

Asthmatic population 

all ages

5,900 4,700 900 1,100 1,300 1,500 1,900 3,000 23,300

Emergency Room 

Visits

All ages

20 15 5 5 5 5 5 10 70

School Absences

Ages 5-17

34,000 28,700 4,900 6,000 8,000 8,200 9,300 18,400 117,500

Days of School 

Absences

Ages 5-17

54,500 45,900 7,800 9,600 12,800 13,100 14,900 29,400 188,000

Minor Restricted 

Activity Days

Ages 18-64

49,900 38,200 9,000 9,200 10,800 13,200 16,200 24,600 171,100
62

Table IV-3 PM2.5-Related Effects

 Fresno Kern Kings Madera Merced San 

Joaquin

Stanislaus Tulare All 

Counties

Minor Restricted 

Activity Days

Ages 18-64

4,610 3,800 870 880 1,050 2,070 2,160 1,840 17,280

Premature Mortality

Ages 30 and older

130 100 15 15 20 65 65 50 460

Work Loss Days 

Ages 18-64

800 660 150 150 180 360 380 320 3,000

Lower Respiratory 

Symptoms 

Ages 5-17

240 195 35 40 60 100 105 100 875

Upper Respiratory 

Symptoms

Asthmatic Children

4,440 3,670 660 760 1,100 1,860 1,940 1,880 16,310

Acute Bronchitis

Ages 5-17

860 750 130 140 210 390 360 390 3,230

Chronic Bronchitis

Ages 27 and older

85 75 15 15 20 40 40 35 325
63

Table IV-4 PM2.5 - Related Deaths Compared to Motor Vehicle Deaths

County Annual PM2.5 - Related Deaths Annual Motor 

Vehicle Deaths6

PM2.5 as % of MV

Kern 100 144 70%

San Joaquin 65 111 59%

Stanislaus 65 97 67%

Merced 20 54 37%

Madera 15 37 41%

Fresno 130 181 72%

Kings 15 34 45%

Tulare 50 89 56%

Total 460 747 62%

 6 Annual average from 2001-2003.
64

V. ECONOMIC VALUATION

V. 1 The Basis for Value

If we know how much illness and premature death might be avoided as a result of 

meeting the health-based air quality standards, why assign monetary values at all, and what is the 

basis for those values? First, there are more worthwhile things to do than either society or 

individuals can afford. As a result, we choose among the things that we do. The social choice to 

control emissions in order to improve air quality and health is one of these things, and one that is 

a high priority for Californians. It is therefore useful to have a sense in economic terms of the 

scale of gains from successfully implementing pollution control policies and programs. This 

study is designed to provide a measure of these gains that is transparent, uses the best available 

information, reflects social preferences and can readily be compared against the value of other 

social choices. 

The basis for each value begins with the premise that, within limits7

, society accepts 

individual choices as valid, and as reflecting the value that individuals place on their choices, 

whether it is which news channel to watch or which college is best for their child to attend. That 

is, what an individual chooses to do accurately represents what is best for him or her, and for 

society, which is simply the sum of the individuals that make up that society. Social value –

what we want to capture here – is then simply the sum of value to individuals. To determine the 

value to individuals of reducing pollution-related health risks we use prices or implied prices 

when available, along with survey (contingent valuation) results.

One objective of this study is to provide a monetary, or dollar, measure of the benefits 

that would accrue from avoiding some of the adverse health effects that result from exposure to 

unhealthful air. A critical aspect of such a measure is determining the value that society places 

on avoiding specific adverse effects. These range from symptoms that are fairly minor, such as 

eye irritation, through hospitalization, emergency room visits, asthma attacks and the onset of 

chronic bronchitis, to premature death. Individuals value reducing these effects to avoid:

• Loss of time (work and school) and the direct medical costs that result from avoiding or 

responding to adverse health effects.

• The pain, inconvenience and anxiety that result from adverse effects, or efforts to avoid 

or treat them.

• Loss of enjoyment and leisure time.

• Adverse effects on others resulting from their own adverse health effects.

V. 2 Concepts and Measures of Value

Ideally, measures of value would represent all of the losses to individuals and to society 

that result from adverse health effects. They would also accurately reflect actual preferences and 

decision-making processes similar to those we use daily to make basic choices. Our decisions 

 7 Most people readily accept limits on individual choices that are necessary to protect others. This includes things 

such as criminal statutes, speed laws, and a variety of environmental protections ranging from vehicular exhaust 

standards to protection of endangered species.
65

about which goods or services to buy are based on which items give the most satisfaction, or 

utility, relative to prices and income. Market prices are therefore accepted as reasonable 

measures of the value of those items that can be purchased. However, there is no market in 

which cleaner air (like many other environmental goods) can be bought. Consequently, values 

for such goods cannot be directly observed from prices. Economists have developed alternatives 

to market prices to measure the value of environmental improvements, including health benefits 

resulting from cleaner air.

Two generally accepted measures of the value of changes in well-being due to reducing 

the adverse health effects of air pollution are the cost of illness (COI) measure and the 

willingness to pay (WTP) or willingness to accept (WTA) measures. All three measures have 

limitations but, when taken together, they yield a generally accepted range of values for the 

health benefits of improvements in air quality. In this study, we use the most appropriate 

available value for each health endpoint.

V. 2.1 Cost of Illness

The COI method was the first to be developed and described in the health and safety 

literature as a basis to value reductions in risk. It requires calculating the actual direct 

expenditures on medical costs, plus indirect costs (lost wages), incurred due to illness. This 

method is still the primary measure used to value the benefit of avoiding hospital admissions and 

other medical treatments. The COI method has the advantage of being based on real dollars 

spent to treat specific health effects and the actual market value of work time. Since it includes 

only monetary losses, however, and does not include losses associated with the value of leisure 

time, of school or unpaid work time, or of general misery, it does not capture all of the benefits 

of better health. The method is therefore generally viewed as limited and representing a lower 

bound on value. The basic limitation is that it is a measure of the financial impact of illness, not 

the change in well being due to illness, since financial loss is only part of the value forfeited by 

illness and discomfort. Other factors, most notably pain, inconvenience and anxiety, associated 

with illness can result in a significant disparity between COI estimates and WTP (or WTA) 

estimates. As discussed below, the COI approach has been shown to produce a lower-bound 

value estimate. Overall, COI measures are used when more complete measures are unavailable 

for a specific effect. While they generally represent a lower bound of value, using them allows 

the valuation of some adverse effects, such as emergency room visits, which might otherwise not 

be quantified.

V. 2.2 Market Based Values

Because we know that COI measures undervalue adverse health effects, many studies 

have been conducted to determine more complete values. For improvements in health, we use 

WTP measures, which are both more complete than COI and consistent with accepted economic 

concepts about markets and individual economic choices. Market choices that reduce risks to 

health or life indirectly indicate the WTP for lower risks, or the WTA for higher risks. Values 

derived from this method are based on relating differences in wages or consumer costs to 

differing degrees of risk. Those differences indicate the demand for and the WTP for lower risk, 

or the WTA for greater risk. Because air quality is not a market commodity and has no 

observable market price, many of the values used in benefit assessments for environmental 

improvements depend on studies of market-determined wage differentials and consumer 
66

expenditures in relation to lower risk of harm from other causes. These differentials and

expenditures are then surrogates for the market price for reduced risk of harm from air pollution.

There is an extensive economics literature assessing the value of reduced workplace risk 

of death. It is, however, important to control for factors other than risk that can influence wage 

differentials, such as unpleasant working conditions. Studies conducted in the past 20 years do 

control carefully for job attributes that are not related to differences in risk. (Viscusi 1992, 1993, 

2004; Viscusi and Aldy 2003) There is a smaller literature that investigates differences in 

consumer expenditures relative to risk of injury or death associated with product use. The results 

for the most carefully conducted work, which controls for product characteristics other than 

relative risk, are generally consistent with the wage-risk studies (Atkinson and Halvorsen 1990; 

Viscusi 1992).

V. 2.3 Contingent Valuation

When values inferred from markets are not available, another means to estimate value 

involves the use of surveys. This method is referred to as contingent valuation (CV) because 

people are asked to determine what something would be worth as if they were able to purchase 

or sell it. CV has become a significant source of values over the past two decades, as the 

methodology has matured and become more accepted, and as policy-makers (and the courts) 

have become more interested in the application of economic values to decision-making. CVbased values, as with wage-risk based WTA values, are conceptually better than COI because 

they are more inclusive. Respondents can value loss of enjoyment and discomfort, as well as the 

direct costs of an adverse health effect. The survey approach is, however, expensive to 

administer and the validity of values derived from this method depends on careful design and 

application of the survey instrument. Nonetheless, CV measures are in many cases wellsupported and add useful information to benefits assessment (Carson et al. 2001).

V. 2.4 Strengths and Limitations of Methods

The most appropriate basis for valuing reductions in adverse health effects is presently WTP 

values based on CV studies and WTA based on wage-risk studies (Viscusi 1993). Cost of illness 

measures are used when preferred measures are unavailable because a lower bound value is 

preferable to zero value, which is implied when an effect is not included in the benefits 

assessment. We use four criteria to choose specific values from the literature.

1. The value used should be appropriate for the type of risk. For example, involuntary risk 

might carry a higher value than voluntary risk. The degree of risk (1 in 10,000 or 1 in 

1,000,000) is a factor, as is whether the risk of harm in increasing or decreasing. 

Whether harm is prospective or has already occurred is also a factor.8

2. A measure should be as complete as possible. That is, it should represent gains or losses 

in well-being as fully as possible.

 8 The human capital method used in damage award legal cases is not used here, for example, because harm has 

already occurred. In assessing the benefits of environmental improvements we are considering the avoidance of 

harm, not compensation for harm.
67

3. If similar values are derived from studies using different methods, for example from 

market-based studies and CV studies, those values are given a greater weight on the 

premise that convergence implies a closer representation of true value.

4. If more than one valid study produces values that are similar for comparable adverse 

affects, those values are given greater weight.

Given these criteria, CV results for WTP are most highly ranked for appropriateness and 

validity, followed by WTA from wage-risk studies (supported by WTP from a valid consumer 

behavior study) and then COI measures.

V. 3 Specific Values for Premature Death

Premature mortality is the most significant effect of exposure to unhealthful levels of air 

pollution that can presently be quantified. Consequently, determining a socially appropriate 

value to attach to reducing the risk of premature mortality is a crucial part of any benefit 

assessment. It is very important to keep in mind that we are not valuing the life of any 

identifiable individual, but rather the value of reducing a very small risk over a large population 

enough so that some people would live longer than would otherwise have been the case. 

V.3.1 The Concept of the Value of a Statistical Life

Wage-risk studies tell us how much more compensation workers must be paid to accept 

jobs with very slightly elevated risks of job-related death. Consider this example:

There are 10,000 workers and the annual risk of job-related death is 1/10,000 greater than 

in a lower wage job. This means that we would expect one job-related death in this group 

annually (10,000 x 1/10,000). Let’s say that each worker is paid $700 a year more as a result of 

this risk, and workers not facing this risk are paid $700 a year less than those at risk. The 

implied value of reducing risk just enough to prevent one death is $700 x 10,000 = $7,000,000. 

This is what economists call the value of a statistical life (VSL). Studies of consumer choices 

and product risk are based on the same approach – the small difference that each consumer pays 

to reduce a slight risk aggregated to the level of reducing risk enough to prevent a single death.

V.3.2 The Range of Values

There is a very wide range across all studies that assess VSL. However, this range can be 

narrowed significantly by considering characteristics of the population in each study relative to 

the population with which we are concerned (the San Joaquin Valley), and by reviewing the 

methods used in each study. In a recent meta-analysis of VSL from US wage-risk studies 

(Viscusi and Aldy 2003), most estimates fell into the range of $3.8-$9.0 million (in 2000 dollars) 

with a median for “prime-aged workers” of $7 million. This range is also consistent with the 

most robust consumer choice study (Atkinson and Halvorsen 1990), which found a VSL of $5.1 

in 2000 dollars. Contingent valuation studies produce values at or above the upper end of the 

Viscusi and Aldy meta-analysis (Viscusi 1993; Jones-Lee 1976).
68

V.3.3 Issues in Selecting Specific Values

To assess the value to society of reducing the risk of premature death associated with 

elevated levels of air pollution, we want a value that is based on risk of a similar scale (in this 

case a very small annual risk) and is based on the preferences of people similar to the population 

at risk from pollution exposure. The need to match the degree of risk and population 

characteristics as closely as possible raises several issues, largely relating to factors such as age 

and income. 

V.3.3.1 Groups Most at Risk

For mortality, we have evidence for the very young – newborns – and those aged 30 and 

over associating elevated pollution with premature death. We also know that the very young, 

those whose health is already compromised, and those aged 65 and older are at greater risk than 

the general population. 

V.3.3.2 Age and the Value of Life

Because wage-risk studies are based largely on blue collar workers, they reflect the 

preferences of younger workers, and not those outside the workforce who are very young or 

older, but who are likely at greater risk of early death related to air pollution. Since younger 

people have longer life expectancies, using a VSL based on their preferences might overstate the 

appropriate VSL for the older. Similarly, it is likely to understate society’s value for young 

children, as several studies indicate that parents and society more broadly place greater value on 

preventing harm to children than to adults. Further, to the extent that blue collar workers have 

incomes below the average, their job choices might reflect a lower VSL than would be the case 

for white collar workers. Complicating this further, older adults are more likely to experience 

impaired health and could therefore have a lower VSL than is the case for a healthy younger or 

middle-aged adult or a child, although evidence suggests that this effect, if any, is small (Alberini 

et al. 2004). In determining which VSL to use to value air quality improvements, these factors 

are all considered. 

The most recent research regarding health status and older age (Alberini et al, 2004) finds 

no strong evidence that VSL declines significantly with age, and then only at age 70 and above. 

Further, those with underlying health conditions report little difference in VSL than those who 

are healthier. At the other end of life, there is evidence (Dickie and Messman 2004; EPA 2003a 

and the references therein) that families and society place a higher value on children’s wellbeing, but there is no well established basis to adjust adult values to account for this. Although 

these are some studies that assess how much more we are willing to pay for children’s health, 

there has been little work regarding how we value their lives.

Consistent with these findings and the recommendations of peer-review advisory groups, 

benefit assessments carried out for proposed federal and state rules and programs (EPA 2003b, 

2004, 2005; ARB 2005) do not make any adjustment for age or health status. 
69

V.3.4 The Value of a Statistical Life Used in this Study

As noted above, the convergence of values from US-based wage-risk studies is $3.8 to 

$9.0 million in 2000 dollars. Converting this to 2005 dollars (using the US all-item CPI) 

produces a range of $4.3 to $10.2 million. The value from a consumer choice study is $5.8 

million in 2005 dollars.

The most recent final EPA regulatory analysis (EPA 2005) used $5.5 million in 1999 

dollars. Converting this to 2005 dollars gives us $6.5 million. We further adjust this for the 

increase in per capita income in California from 1999 to 20049

, and assume an income elasticity 

of 0.510

V. 4 Specific Values for Health Endpoints

(Viscusi and Aldy 2003). This leads to a VSL of $6.7 million, which is the value used in 

this study.

Generally accepted values for many endpoints have been developed over the past decade 

and are widely used in benefit assessments and regulatory analyses by USEPA and the states. 

These values have been peer-reviewed by advisory bodies, including committees of EPA’s 

Scientific Advisory Board, and many have also been published in the peer reviewed literature. 

We generally follow this established protocol, adjusting specific values for inflation and 

California-specific incomes. Where California-specific COI data are available, as for 

hospitalizations, we use those values.

Onset of Chronic Bronchitis

Apart from premature death, the onset of chronic bronchitis is one of the most serious 

adverse effects that is associated with PM exposure and is quantifiable. The value of avoiding 

this effect has been estimated in two CV studies (Krupnick and Cropper 1989; Viscusi et al. 

1991) and is $374,000 in current dollars, beginning with the value used by EPA (2003b; 2004; 

2005) to account for the severity of the disease relative to the underlying studies.

Hospitalizations

Respiratory-related hospitalizations are costly both in terms of treatment and loss of 

work, household and leisure time. We use a California-based value derived from Chestnut et al. 

(2006), of $32,000 per admission. While Chestnut et al. assessed the COI and WTP for adults, 

we apply this value to the entire population because when children are hospitalized, one or more 

adults faces the opportunity cost of time diverted from work, caring for other children and other 

normal activities.

Minor Restricted Activity Days

Willingness to pay to avoid a day when normal activities are limited by a combination of 

pollution-related symptoms derives from Tolley et al.’s 1986 study, reported by EPA (2005) as 

 9 The most recent final data available.

10 As incomes rise, consumers place greater value on many goods. The degree to which this value rises with income 

and leads to more consumption of a good is called income elasticity. While EPA most recently used 0.4 as the 

adjustment for this effect, Viscusi and Aldy found that the appropriate value for the income elasticity of VSL is 0.5-

0.6.
70

$51 in 1999 dollars and 1990 income. ARB (2005) converted this to current dollars and adjusted 

for income, yielding a value of $61 per MRAD.

Work Loss Days

Apart from MRADs, when productivity might be lower, some work days are lost outright 

as a result of PM2.5 exposure. These days are valued at the daily wage rate for each county, 

ranging from $123 in Merced to $141 in Kern and San Joaquin (EDD 2003).

School Absence Days

To value days of school absence, Smith et al. (1997) estimated lost productivity to the 

adult care-giver, under the assumption that one adult stayed home to take care of the sick child. 

In situations where two caregivers were involved, the lower income was used to estimate lost 

productivity. In cases where only one adult had an income (about 39 percent of the cohort 

studied), an imputed value for household work was used. 

Using this methodology, Smith et al. estimated the total indirect cost of 3.6 million 

school loss days to be $194.5 million (in 1994 dollars) This translates into a per-day value of 

$54.03 (again, in 1994 dollars).

To apply these national figures to our analysis, two adjustments were then made. First, 

the value was updated to 2005 dollars. Second, it was modified to reflect wage levels in the SJV. 

This is the approach adopted by EPA (2005) and used by Hall et al. (2003). This method 

produces a range of values from $65 in Tulare County to $79 in San Joaquin County.

Upper and Lower Respiratory Symptom Days

For these effects we adjusted the value that EPA (2005) has adopted, again adjusting for 

income and inflation to 2005 values. A lower respiratory symptom day is valued at $20 and an 

upper respiratory day at $32.

Acute Bronchitis

Bronchitis typically involves multiple symptoms and each occurrence has a duration of 

about six days (EPA 2005). To construct a value for this effect, we combine Loehman et al.’s 

(1979) values for chest discomfort and cough and update this number to 2005 dollars, producing 

a value for one day of $18.30. Over a six day period, this reaches a total of $110.

Asthma Attack

This effect is valued based on a 1986 CV study conducted in Los Angeles (Rowe and 

Chestnut) that estimated WTP to avoid a “bad asthma day.” Adjusting EPA’s most recent peerreviewed figure to current dollars and adjusting for income, this value is $50 per event.
71

Emergency Room Visits

Emergency room visits are valued at $335 in 2005 dollars based on two combined COI 

studies (EPA 2005). This dollar measure does not include time lost at work or school, or the 

value of avoiding the pain and anxiety caused by the underlying condition and ER visit.

V. 5 Estimated Economic Value from Reduced Adverse Health Effects with Attainment 

of the NAAQS for Ozone and PM2.5 

Unsurprisingly, given the great value that individuals and society more broadly place on 

life, the overall benefits of attaining the NAAQS are dominated by premature mortality. Across 

the Valley 460 people are estimated to avoid premature death each year, accounting only for the 

effect of PM2.5 and only for the population age 30 and older. With a value for each life of $6.7 

million, this effect alone offers a benefit of attainment of more than $3 billion each year. While 

this consequence of elevated fine particle levels is by far the most striking, other effects are also 

important.

For example, an additional 325 new cases of chronic bronchitis annually could be 

avoided with attainment of the PM2.5 NAAQS. At a value of $374,000 each – reflecting the 

significant costs of treatment and loss of enjoyment and activity – avoiding this effect would 

generate benefits of over $120 million annually. Ozone attainment offers thousands fewer 

school absence days, conservatively valued at nearly $13 million a year. It should be noted that 

this only reflects the value of time lost to an adult caregiver and not any medical costs or loss of 

educational opportunity. Minor restricted activity days (MRADs) would cost adults over 

190,000 days a year when their daily routine is limited to some degree by exposure to elevated 

ozone or PM2.5 . Avoiding this offers an economic benefit over $10 million annually.

Tables V-1 and V-2 show the overall benefits, both in numbers of effects and in dollars 

for ozone and for PM2.5, respectively. Looking at the overall benefits, residents of the San 

Joaquin Valley could expect annual benefits of $3.2 billion if both the ozone and PM2.5 NAAQS 

were attained.

It is also worth considering the per capita benefits, to provide a sense of perspective. On a 

Valley-wide average, annual benefits are nearly $1,000 per person. This varies across counties 

with the levels of pollution and the size of the more vulnerable populations, and very slightly 

with income (which determines or influences the value of some effects). The county-level 

average benefits per resident range from nearly $650 in Merced County to over $1,200 in Kern 

County.11

 11 Fresno $1,124; Kern $1,209; Kings $785; Madera $679; Merced $645; San Joaquin $789; Stanislaus $973; Tulare 

$1,020; all counties $970.
72

Table V-1 Ozone-Related Effects and Economic Value

Fresno Kern Kings Madera Merced San 

Joaquin

Stanislaus Tulare Total

Respiratory Hospital 

Admissions

Ages 0-64

55 45 10 10 10 15 20 30 195

Respiratory Hospital 

Admissions

Ages 65+

25 15 0 5 5 0 5 10 65

Respiratory Hospital 

Admissions

All ages

80 60 10 15 15 15 25 40 260

 

Value(millions)

$2.56 $1.92 $0.32 $0.48 $0.48 $0.48 $0.8 $1.28 $8.32

Asthma Attacks

Asthmatic population 

all ages

5,900 4,700 900 1,100 1,300 1,500 1,900 3,000 23,300

 

Value(thousands)

$295 $235 $45 $55 $65 $75 $95 $150 $1,015

Emergency Room 

Visits

All ages

20 15 5 5 5 5 5 10 70

 

Value (thousands) 

$6.70 $4.31 $1.68 $1.68 $1.68 $1.68 $1.68 $3.35 $23.45

School Absences

Ages 5-17

34,000 28,700 4,900 6,000 8,000 8,200 9,300 18,400 117,500

Days of School

Absences

Ages 5-17

54,500 45,900 7,800 9,600 12,800 13,100 14,900 29,400 188,000

 

Value(millions)

$3.60 $3.12 $0.53 $0.66 $0.87 $1.03 $1.13 $1.91 $12.85

Minor Restricted 

Activity Days

Ages 18-64

49,900 38,200 9,000 9,200 10,800 13,200 16,200 24,600 171,100

 

Value(millions)

$3.04 $2.33 $0.55 $0.56 $0.66 $0.80 $0.99 $1.5 $10.43

Total Value in 

Millions

$9.5 $7.61 $1.45 $1.76 $2.08 $2.39 $3.02 $4.84 $32.64
73

Table V-2 PM2.5-Related Effects and Economic Value

 Fresno Kern Kings Madera Merced San 

Joaquin

Stanislaus Tulare All 

Counties

Minor Restricted 

Activity Days

Ages 18-64

4,610 3,800 870 880 1,050 2,070 2,160 1,840 17,280

 

Value(thousands)

$281.2 $231.8 $53.1 $53.7 $64.1 $126.3 $131.8 $112.2 $1,054.2

Premature Mortality

Ages 30 and older

130 100 15 15 20 65 65 50 460

 

Value(millions)

$871.0 $670.0 $100.5 $100.5 $134.0 $435.5 $435.5 $335.0 $3,082.0

Work Loss Days 

Ages 18-64

800 660 150 150 180 360 380 320 3,000

 

Value(thousands)

$106.0 $93.1 $21.0 $19.8 $22.0 $50.8 $52.0 $39.7 $403.8

Lower Respiratory 

Symptoms 

Ages 5-17

240 195 35 40 60 100 105 100 875

 

Value(thousands)

$4.8 $3.9 $0.7 $0.8 $1.2 $2.0 $2.1 $2.0 $17.5

Upper Respiratory 

Symptoms

Asthmatic Children

4,440 3,670 660 760 1,100 1,860 1,940 1,880 16,310

 

Value(thousands)

$142.1 $117.4 $21.1 $24.3 $35.2 $59.5 $62.1 $60.2 $521.9

Acute Bronchitis

Ages 5-17

860 750 130 140 210 390 360 390 3,230

 

Value(thousands)

$94.6 $82.5 $14.3 $15.4 $23.1 $42.9 $39.6 $42.9 $355.3

Chronic Bronchitis

Ages 27 and older

85 75 15 15 20 40 40 35 325

 

Value (millions)

$31.8 $28.1 $5.6 $5.6 $7.5 $15.0 $15.0 $13.1 $121.6

Total Value in 

Millions

$903.4 $698.6 $106.2 $106.2 $141.6 $450.8 $450.8 $348.4 $3,206
74

VI. CONCLUSIONS AND IMPLICATIONS

Conclusions

Almost every resident of the San Joaquin Valley regularly experiences air pollution levels 

known to harm health and to increase the risk of early death. For example, from 2002 through 

2004 each person was on average exposed to unhealthful levels of ozone on 70 days a year. 

Even in the county with the lowest exposure (San Joaquin County) residents were exposed to 

levels over the California 8-hour standard on ten days each year. In Kern County, this rises to 

over 100 days each year. This is unsurprising, given how frequently and pervasively the healthbased air quality standards are violated. These exposures translate directly into poorer health 

and an elevated risk of premature death. Further, some groups are more at risk than the average, 

with Hispanics experiencing six more days of ozone exposure above the California air quality 

standard than the average resident. 

Some other noteworthy results of the analysis include:

• Valley-wide, the economic benefits of meeting the federal PM2.5 and ozone standards 

average nearly $1,000 per person per year, or a total of more than $3 billion. 

This dollar value represents the following:

• 460 fewer premature deaths among those age 30 and older

• 325 fewer new cases of chronic bronchitis

• 188,400 fewer days of reduced activity in adults

• 260 fewer hospital admissions

• 23,300 fewer asthma attacks

• 188,000 fewer days of school absence

• 3,230 fewer cases of acute bronchitis in children

• 3,000 fewer work loss days

• More than 17,000 fewer days of respiratory symptoms in children

To place the reduction in premature deaths in perspective, attaining the federal PM2.5 

standard would be the equivalent of reducing motor vehicle deaths by over 60% Valley-wide, 

and by more than 70% in Fresno and Kern Counties.

Implications

Residents of the San Joaquin Valley face significant public health risks from the present 

unhealthful levels of ozone and fine particles. This is in addition to other health challenges, 

including a high rate of poverty, which exceeds 30% in Fresno County, compared to a statewide 

rate below 20%. The region overall would experience substantial economic and health gains 

from effective policies to reduce pollution levels. For the more populous and more polluted 

areas in Kern and Fresno Counties, this is even more pronounced. Attaining the California air 

quality standards, which are more protective of health, would double the health benefits listed 

above.
75

The adverse impacts of air pollution are not distributed equally. Both Hispanics and nonHispanic blacks are exposed to more days when the health-based standards are violated. 

Residents of Fresno and Kern Counties experience many more days when the PM2.5 standards 

are violated than the Valley-wide average. Tulare County joins Fresno and Kern in being well 

above average for the number of days of exposure above the ozone standards. Children under age 

5 are exposed to ozone concentrations above 70 ppb on more days than older adults. 

Because ozone is elevated during the summer months, and the PM2.5 24-hour standard is 

typically violated more frequently in the winter months, there is no “clean” season in this region.

As the population continues to increase, with associated increases in vehicle traffic and 

economic activity, the gains from attaining the health-based air quality standards will grow, but 

also become more difficult to achieve. Identifying and acting on opportunities now would 

produce substantial gains to the people of the Valley.
76

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82

APPENDIX

A.1 The Benefits of Attaining the California Ambient Air Quality Standards

The state health-based standards for ozone and PM2.5 provide a greater degree of 

protection than do the federal standards. Consequently, the benefits of attaining the California 

Ambient Air Quality Standards (CAAQS) are significantly larger. While the present focus is on 

attainment of the NAAQS, there is clear evidence that health will continue to be impaired until 

the CAAQS are also attained. The health-related benefits of attaining the ozone CAAQS are 

shown in Table A-1. PM2.5 –related benefits are shown in Table A-2. It should be noted that 

there is no separate state 24-hour standard for PM2.5, so only effects associated with longer term 

(annual average) exposure are included here. Generally, attaining the California standards would 

approximately double the gains that will result from meeting the NAAQS.
83

Table A-1 Reductions in Ozone-Related Health Effects Resulting from CAAQS Attainment 

Fresno Kern Kings Madera Merced San 

Joaquin

Stanislaus Tulare Total

Respiratory Hospital 

Admissions

Ages 0-64

120 85 15 20 20 35 40 60 395

Respiratory Hospital 

Admissions

Ages 65+

55 35 5 10 10 0 10 25 150

Respiratory Hospital 

Admissions

All ages

175 120 20 30 30 35 50 85 545

 

Value(millions)

$5.60 $3.84 $0.64 $0.96 $0.96 $1.12 $1.60 $2.72 $17.44

Asthma Attacks

Asthmatic population 

all ages

12,600 9,300 1,900 2,300 2,800 3,500 4,200 6,100 42,700

 

Value(thousands)

$630 $465 $95 $115 $140 $175 $210 $305 $2,135

Emergency Room 

Visits

All ages

30 20 5 5 5 10 10 15 100

 

Value (thousands) 

$8.61 $5.74 $1.44 $1.44 $1.44 $2.87 $2.87 $4.31 $28.72

School Absences

Ages 5-17

78,200 59,900 11,000 13,800 18,900 19,800 22,200 38,800 262,600

Days of School 

Absences

Ages 5-17

125,100 95,800 17,600 22,100 30,200 31,700 35,500 62,100 420,100

 

Value(millions)

$8.26 $6.51 $1.20 $1.52 $2.05 $2.50 $2.70 $4.04 $28.80

Minor Restricted 

Activity Days

Ages 18-64

96,800 69,400 16,100 18,100 21,000 27,400 31,700 43,900 322,400

 

Value(millions)

$5.90 $4.23 $0.98 $1.10 $1.28 $1.67 $1.93 $2.68 $19.80

Total Value in 

Millions

$20.40 $15.06 $2.92 $3.71 $4.44 $5.47 $6.44 $9.74 $68.18
84

Table A-2 Reductions in PM2.5 -Related Health Effects Resulting from CAAQS Attainment 

Fresno Kern Kings Madera Merced San 

Joaquin

Stanislaus Tulare Total

Premature 

Mortality

Ages 30 and older

240 180 30 30 40 120 130 110 880

 

Value(millions)

$1,608.0 $1,206.0 $201.0 $201.0 $268.0 $804.0 $871.0 $737.0 $5,896.0

Acute Bronchitis

Ages 5-17

1,540 1,290 240 250 380 740 700 780 5,920

 

Value(thousands)

$169.4 $141.9 $26.4 $27.5 $41.8 $81.4 $77.0 $85.8 $651.2

Chronic Bronchitis

Ages 27 and older

155 130 30 30 35 80 75 75 610

 

Value (millions) 

$58.0 $48.6 $11.2 $11.2 $13.1 $29.9 $28.0 $28.0 $228.1

Total Value in 

Millions

$1,666.2 $1,254.7 $212.2 $212.2 $281.1 $834.0 $899.1 $765.1 $6,124.7

A.2 Sensitivity Analysis by Endpoint 

The results presented in Sections IV and V above report a mid-value for each effect, 

based on a professional consensus regarding the concentration-response relationships that “best” 

represent the association between exposure and resulting adverse health effects. It is generally 

accepted, however, that the real association lies within a range. Here we present the results of 

sensitivity tests that estimate benefits based on such a range, generally based on 95% confidence 

intervals. Unsurprisingly, this analysis produces a wide range in the results, and the results are 

shown in Tables A-3 and A-4. 

There is one noteworthy result, which is the high estimate for premature mortality, 

indicating over 1,200 deaths a year associated with violations of the NAAQS for PM2.5 , in 

contrast to 460 estimated with the mid-range concentration-response function. The difference 

results entirely from the use of Pope et al.’s (2002) central value for the “base” case and Jerrett et 

al.’s (2005) result for the high case. As noted in section IV, Jerrett et al. is likely a better 

representation of risk for the SJV population than is the Pope et al. result, a conclusion reached 

by several peer reviewers who addressed this question recently for ARB (CARB 2005). 
85

Table A-3 Ozone-Related Effects Low and High Case Ranges

Adverse Effect All Counties – Range of Effects All Counties – Range of Value

Respiratory Hospital Admissions

All ages

150-360 $4,800,000 – 11,520,000

Asthma Attacks

Asthmatic population all ages

4,670-35,690 $233,500 – 1,785,000

Emergency Room Visits

All ages

40-80 $11,480 – 22,960

Days of School Absences

Ages 5-17

88,560-282,300 $3,786,000 – 12,070,000

Minor Restricted Activity Days

Ages 18-64

69,500-270,400 $4,240,000 – 16,490,000

Table A-4 PM2.5-Related Effects Low and High Case Ranges

Adverse Effect All Counties – Range of Effects All Counties – Range of Value

Minor Restricted Activity Days

Ages 18-64

14,070-20,460 $858,270 - $1,248,060

Premature Mortality

Ages 30 and older

160-1,220 $1,072,000,000 - $8,174,000,000

Work Loss Days 

Ages 18-64

2,540-3,470 $342,800 – 466,400

Lower Respiratory Symptoms 

Ages 5-17

195-1510 $3,900-30,000

Upper Respiratory Symptoms

Asthmatic Children

2,770-29,370 $88,640 – 939,800

Acute Bronchitis

Ages 5-17

1,240-5,070 $136,400 – 557,700

Chronic Bronchitis

Ages 27 and older

165-480 $61,710,000 - $179,500,000