CHAPTER 2 

AIR QUALITY AND HEALTH EFFECTS 

Introduction 

Ambient Air Quality Standards 

Comparison to Other U.S. Areas 

Current Air Quality Summary
Chapter 2 Air Quality and Health Effects 

2 - 1 

INTRODUCTION 

In this chapter, year 2001 air quality in the South Coast Air Basin (Basin), and in the 

portion of the Salton Sea Air Basin (SSAB) monitored by the South Coast Air Quality 

Management District (District), is compared to state and federal ambient air quality 

standards. For those pollutants for which the Basin is in nonattainment of the federal 

standards, maps have been included which compare the year 2001 air quality in different 

areas of the Basin.1

 Nationwide air quality for 2001 is also briefly summarized in this 

chapter. A comparison of air quality in the Basin to other U.S. and California urban areas 

is presented in the following pages. 

AMBIENT AIR QUALITY STANDARDS 

Ambient air quality standards for ozone, carbon monoxide, nitrogen dioxide, sulfur 

dioxide, particulate matter (PM10 and PM2.5), and lead have been set by both the 

California state and federal governments. The state has also set standards for sulfate and 

visibility. The ambient air quality standards for each of these pollutants and their effects 

on health are summarized in Table 2-1. 

In 2001, the Basin exceeded the federal standards for ozone, PM10 and PM2.5 on a total 

of 58 days. Despite the substantial improvement over historical air quality in the past 

few decades, some areas in the Basin still exceed the 1-hour federal standard for ozone 

more frequently than any other area of the U.S. In 2001, nine out of ten locations in the 

nation that exceeded the standard most frequently were located in the Basin and the Basin 

is currently the only area in the nation classified as "extreme" nonattainment for ozone. 

The Basin is also among the few areas in the nation that still is classified as 

nonattainment for carbon monoxide. (The Basin has technically met the CO standards in 

2002 and the District will request reclassification as attainment in the next few years.) 

COMPARISON TO OTHER U.S. AREAS 

The Basin’s severe air pollution problem is a consequence of the combination of 

emissions from the nation’s second largest urban area and meteorological conditions 

which are adverse to the dispersion of those emissions. The average wind speed for Los 

Angeles is the lowest of the nation’s ten largest urban areas. In addition, the summertime 

maximum mixing height (an index of how well pollutants can be dispersed vertically in 

the atmosphere) in Southern California averages the lowest in the U.S. The Southern 

California area is also an area with abundant sunshine, which drives the photochemical 

reactions which form pollutants such as ozone. 

 

1

 Complete data for the year 2002 is not available at this time. 
Final 2003 AQMP 

2 - 2 

TABLE 2-1 

Ambient Air Quality Standards* 

 STATE STANDARD FEDERAL PRIMARY STANDARD MOST RELEVANT EFFECTS 

AIR 

POLLUTANT 

CONCENTRATION/ 

AVERAGING TIME 

CONCENTRATION/ 

AVERAGING TIME 

Ozone 0.09 ppm, 1-hr. avg. > 0.12 ppm, 1-hr avg.> 

0.08 ppm, 8-hr avg.> 

(a) Short-term exposures: (1) Pulmonary 

function decrements and localized lung edema 

in humans and animals. (2) Risk to public 

health implied by alterations in pulmonary 

morphology and host defense in animals; (b) 

Long-term exposures: Risk to public health 

implied by altered connective tissue metabolism 

and altered pulmonary morphology in animals 

after long-term exposures and pulmonary 

function decrements in chronically exposed 

humans; (c) Vegetation damage; (d) Property 

damage 

Carbon Monoxide 9.0 ppm, 8-hr avg. > 

20 ppm, 1-hr avg. > 

9 ppm, 8-hr avg.> 

35 ppm, 1-hr avg.> 

(a) Aggravation of angina pectoris and other 

aspects of coronary heart disease; (b) Decreased 

exercise tolerance in persons with peripheral 

vascular disease and lung disease; (c) 

Impairment of central nervous system functions; 

(d) Possible increased risk to fetuses 

Nitrogen Dioxide 0.25 ppm, 1-hr avg. > 0.053 ppm, ann. avg.> (a) Potential to aggravate chronic respiratory 

disease and respiratory symptoms in sensitive 

groups; (b) Risk to public health implied by 

pulmonary and extra-pulmonary biochemical 

and cellular changes and pulmonary structural 

changes; (c) Contribution to atmospheric 

discoloration 

Sulfur Dioxide 0.04 ppm, 24-hr avg.> 

0.25 ppm, 1-hr. avg. > 

0.03 ppm, ann. avg.> 

0.14 ppm, 24-hr avg.> 

(a) Bronchoconstriction accompanied by 

symptoms which may include wheezing, 

shortness of breath and chest tightness, during 

exercise or physical activity in persons with 

asthma 

Suspended 

Particulate Matter 

(PM10)** 

30 μg/m3, ann. geometric mean > 

50 μg/m3, 24-hr average> 

50 μg/m3, ann. arithmetic mean > 

150μg/m3, 24-hr avg.> 

Suspended 

Particulate Matter 

(PM2.5)** 

15 μg/m3, ann. arithmetic mean > 

65 μg/m3, 24-hr avg.> 

(a) Excess deaths from short-term exposures and 

exacerbation of symptoms in sensitive patients 

with respiratory disease; (b) Excess seasonal 

declines in pulmonary function, especially in 

children; (c) Increased risk of premature death 

from heart or lung diseases in elderly 

Sulfates 25 μg/m3, 24-hr avg. ≥ (a) Decrease in ventilatory function; (b) 

Aggravation of asthmatic symptoms; (c) 

Aggravation of cardio-pulmonary disease; (d) 

Vegetation damage; (e) Degradation of 

visibility; (f) Property damage 

Lead 1.5 μg/m3, 30-day avg. ≥ 1.5 μg/m3, calendar quarter> (a) Increased body burden; (b) Impairment of 

blood formation and nerve conduction 

VisibilityReducing 

Particles 

In sufficient amount such that the 

extinction coefficient is greater 

than 0.23 inverse kilometers (to 

reduce the visual range to less 

than 10 miles) at relative humidity 

less than 70 percent, 8-hour 

average (10am - 6pm) 

 Visibility impairment on days when relative 

humidity is less than 70 percent 

 * For readers' convenience in picking out standards quickly, concentration appears first; e.g. "0.12 ppm, 1-hr avg. >" means 1-hr avg. > 0.12 ppm. 

** New and stricter state standards for PM are proposed and adopted by ARB. They include: PM10 annual average of 20 μg/m3

 and new PM2.5 

annual average of 12 μg/m3. 
Chapter 2 Air Quality and Health Effects 

2 - 3 

In the Basin, high concentrations of ozone are normally recorded during the spring and 

summer months. By contrast, high concentrations of carbon monoxide are generally 

recorded in late fall and winter. High PM10 and PM2.5 concentrations can occur 

throughout the year, but occur most frequently in fall and winter. Although there are 

changes in emissions by season, the observed variations in pollutant concentrations are 

largely a result of seasonal differences in weather conditions. 

In the year 2001, the federal standard for ozone was exceeded at one or more Basin 

locations on 10 percent of days (36 days). The federal PM10 standard was exceeded on 4 

percent of the days sampled (2 days) and the federal PM2.5 standard was exceeded on 6 

percent of the days sampled (23 days) 2. For the first time since monitoring began, the 

federal carbon monoxide standards were not exceeded in the Basin in the year 2001. The 

Basin is among the few locations in the nation still exceeding carbon monoxide standards 

in the recent years. 

Figure 2-1 shows maximum pollutant concentrations in 2001 for the South Coast Air 

Basin compared to other urban areas in the U.S. and California. Maximum 

concentrations in some of these other large U.S. urban areas exceeded the federal ozone 

or PM10 standards. In California, all of the other large urban areas shown in Figure 2-1 

exceeded the ozone standard. The PM10 standard was exceeded in one of the areas 

shown. None of the areas shown in Figure 2-1 exceeded the carbon monoxide standard. 

In 2001, the Houston metropolitan area recorded the highest maximum 1-hour average 

ozone concentration in the nation (0.194 ppm). The highest concentration in the Basin 

was more than one and a half times the federal standard (0.190 ppm). Houston, like Los 

Angeles, is an area with abundant sunshine which creates favorable conditions for the 

photochemical reactions that yield ozone and other photochemical pollutants. 

In California, the San Joaquin Valley, Sacramento Valley and San Diego Air Basins 

exceeded the 1-hour ozone standard by smaller margin than the South Coast Air Basin. 

San Francisco and South Central Coast Basins barely exceeded the standard. San Diego 

and South Central Coast Air Basins, located immediately south and north of the South 

Coast Air Basin, respectively, are subject to ozone transport from the South Coast Air 

Basin. 

Maximum annual average PM10 concentrations exceeded the federal annual average 

PM10 standard in the Basin and Phoenix and in the San Joaquin Valley Air Basin. 

 

2

 Particulate matter exceedances may have been higher since PM10 samples are collected only every 6 days (except for 

two sites at which samples are collected every 3 days); PM2.5 samples are collected every 3 days at most sites except for 

a few sites which are sampled every day. The gaseous pollutants such as ozone and carbon monoxide are sampled 

continuously. 
Final 2003 AQMP 

2 - 4 

A) South Coast Air Basin Compared to Major U.S. Metropolitan Areas 

B) South Coast Air Basin Compared to Other Air Basins in California 

FIGURE 2-1 

2001 Air Quality 

Maximum Pollutant Concentrations as Percentages of the Federal Standard 

0

50

100

150

200

South Coast Houston Philadelphia New York Washington

D.C.

Atlanta Chicago Phoenix Denver

Ozone Carbon Monoxide PM10 Nitrogen Dioxide Sulfur Dioxide

Percent of Federal Standard

STANDARD

0

20

40

60

80

100

120

140

160

South Coast San Joaquin Valley Sacramento Valley San Diego San Francisco South Central

Coast

Ozone Carbon Monoxide PM10 Nitrogen Dioxide Sulfur Dioxide

Percent of Federal Standard

STANDARD
Chapter 2 Air Quality and Health Effects 

2 - 5 

In the year 2001, no location in the Basin or any other area of the U.S. exceeded the 

nitrogen dioxide standards. The Los Angeles county portion of the Basin was the last 

area of the U.S. to exceed the federal standard for nitrogen dioxide, but has remained in 

compliance since 1991. Sulfur dioxide concentrations in the Basin continued to remain 

well below federal standards. Concentrations of sulfur dioxide in urban areas in the 

Eastern U.S. have generally been higher than those in the Basin due to the use of fuels 

such as coal which have relatively high sulfur content. 

CURRENT AIR QUALITY SUMMARY 

Figure 2-2 shows the maximum pollutant concentrations in the Basin for 2001 as 

percentages of the federal standards compared to the years 1990 and 1980. In 2001, the 

maximum ozone, PM10 and PM2.5 concentrations exceeded federal standards by wide 

margins. Maximum 1-hour and 8-hour average ozone concentrations recorded (0.190 

ppm in East San Gabriel Valley and 0.144 ppm in Central and East San Bernardino 

Valley areas) were 152 and 169 percent of the federal standard, respectively. Maximum 

24-hour average and annual average PM10 concentrations (219 μg/m3

 recorded in 

Banning Airport area and 63.1 μg/m3 recorded in the Metropolitan Riverside County 

area) were 146 and 125 percent of the federal 24-hour and annual average standards, 

respectively. Maximum 24-hour average and annual average PM2.5 concentrations (98.0 

μg/m3

 and 31.1 μg/m3, both recorded in Metropolitan Riverside County area) were, 

respectively, 150 and 201 percent of the federal 24-hour and annual average standards, 

respectively. Carbon monoxide concentration did not exceed the standards in 20013

. 

The highest 8-hour average carbon monoxide concentration recorded (7.71 ppm in the 

South Central Los Angeles County area) was 81 percent of the federal carbon monoxide 

standard. 

Concentrations of other pollutants remained below the standards. The maximum annual 

average nitrogen dioxide concentration (0.0419 ppm recorded in the East San Fernando 

Valley area) was 78 percent of the federal standard, and the maximum annual average 

sulfur dioxide concentration (0.0031 ppm recorded in Southwest Coastal Los Angeles 

County area) was 10 percent of the federal standard. The maximum sulfate concentration 

recorded (20.6 μg/m3

 in Southwest Coastal Los Angeles County area) was 82 percent of 

the state sulfate standard. The maximum quarterly average lead concentration recorded 

at any District air monitoring station was 8 percent of the federal standard. However, 

higher concentration of lead (32 percent of the standard) was recorded at special 

monitoring sites immediately adjacent to stationary sources (in Central Los Angeles 

area). 

 

3

 Preliminary data from 2002 indicates one violation of CO, which is allowed under the Clean Air Act for attainment 

classification purpose. 
Final 2003 AQMP 

2 - 6 

Figure 2-3 shows the percent of days on which the federal standards were exceeded in 

2001 at the Basin locations which exceeded most frequently compared to previous years. 

The federal ozone standard was exceeded on a maximum of 26 days (seven percent of 

days in the Central San Bernardino Mountains area). Exceedances of the federal 24-hour 

PM10 standard were recorded on a maximum of one day (two percent of days sampled at 

each of the locations in Banning Airport and Southwest San Bernardino Valley area), and 

the federal 24-hour PM2.5 standard was exceeded on a maximum of 19 days (6 percent 

of days sampled, in Metropolitan Riverside County area). 

Detailed analyses of current air quality and statistics for all monitoring areas are 

contained in Appendix II. The following sections present summary information on 

health effects and how frequently, and by how much of a margin, different areas of the 

Basin and SSAB exceeded the federal and state ambient air quality standards in 2001. 
Chapter 2 Air Quality and Health Effects 

2 - 7 

* Carbon monoxide standard was exceeded in 2002. 

** There is no federal standard for sulfate. 

*** Higher lead concentrations were recorded at special monitoring sites immediately adjacent to sources. 

FIGURE 2-2 

Maximum Pollutant Concentrations as Percent of Federal Standards 

FIGURE 2-3 

Percent of Days Exceeding Federal Standards at Most Affected Locations 

STANDARD

NO DATANO DATA

Percent of Standard

0

100

200

300

400

500

 Ozone 

(1-Hour)

Carbon* 

Monoxide 

(8-Hour) 

Nitrogen

Dioxide

(Annual)

Sulfur

Dioxide

(Annual)

PM2.5

(Annual)

PM10

(Annual)

Sulfate** 

(24-Hour)

Lead***

(Quarter)

1980

1990

2001

Standard 

Percent of Days Exceeding

0%

20%

40%

60%

80%

100%

Any Standard

Basin-Day

Ozone

(1-Hour)

Carbon

 Monoxide

 (8-Hour)

PM10

 (24-Hour)

PM2.5

 (24-Hour)

1985

1990

1995

2001

NO 

DATA 
Final 2003 AQMP 

2 - 8 

Ozone (O3) Specific Information 

Health Effects

Individuals exercising outdoors, children and people with preexisting lung disease such 

as asthma and chronic pulmonary lung disease are considered to be the most susceptible 

sub-groups for ozone effects. Short-term exposures (lasting for a few hours) to ozone at 

levels typically observed in Southern California can result in breathing pattern changes, 

reduction of breathing capacity, increased susceptibility to infections, inflammation of 

the lung tissue, and some immunological changes. Elevated ozone levels are associated 

with increased school absences. In recent years, a correlation between elevated ambient 

ozone levels and increases in daily hospital admission rates, as well as mortality, has also 

been reported. An increased risk for asthma has been found in children who participate 

in multiple sports and live in high ozone communities. 

Ozone exposure under exercising conditions is known to increase the severity of the 

above mentioned observed responses. Animal studies suggest that exposures to a 

combination of pollutants which include ozone may be more toxic than exposure to 

ozone alone. Although lung volume and resistance changes observed after a single 

exposure diminish with repeated exposures, biochemical and cellular changes appear to 

persist, which can lead to subsequent lung structural changes. 

Air Quality

In 2001, the South Coast Air Quality Management District regularly monitored ozone 

concentrations at 28 locations in the Basin and SSAB. All areas monitored were below 

the stage 1 episode level (0.20 ppm), but the maximum concentrations in the Basin 

exceeded the health advisory level (0.15 ppm). Maximum ozone concentrations in the 

SSAB areas monitored by the District were lower than in the Basin and were below the 

health advisory level. Tables 2-2 and 2-3 show maximum 1-hour and 8-hour ozone 

concentrations by air basin and county. 
Chapter 2 Air Quality and Health Effects 

2 - 9 

TABLE 2-2 

2001 Maximum 1-Hour Ozone Concentrations by Basin and County 

Basin/County 

Maximum 

1-Hr Avg. 

ppm 

Percent of 

Federal 

Standard 

Area 

South Coast Air Basin 

Los Angeles 0.190 152 East San Gabriel Valley 

Orange 0.125 100 Saddleback Valley 

Riverside 0.152 122 Perris Valley 

San Bernardino 0.184 147 Central San Bernardino Valley 

Salton Sea Air Basin 

Riverside 0.137 110 Coachella Valley 

TABLE 2-3 

2001 Maximum 8-Hour Ozone Concentrations by Basin and County 

Basin/County 

Maximum 

8-Hr Avg. 

ppm 

Percent of 

Federal 

Standard 

Area 

South Coast Air Basin 

Los Angeles 0.135 159 East San Gabriel Valley 

Orange 0.098 115 Saddleback Valley 

Riverside 0.136 160 Perris Valley 

San Bernardino 0.144 169 Central San Bernardino 

Valley, 

 East San Bernardino Valley 

Salton Sea Air Basin 

Riverside 0.114 134 Coachella Valley 

The number of days exceeding the federal standard varied widely by area. Figure 2-4 

shows the number of days exceeding the 1-hour ozone federal standard in different areas 

of the Basin. Areas along or nearby the coast did not exceed the federal standard, due in 

large part to the prevailing sea breeze which transports polluted air inland before high 

ozone concentrations can be reached. The standard was exceeded most frequently in the 

inland valleys extending from East San Gabriel Valley through the Riverside-San 

Bernardino area, and in the adjacent mountains. The Central San Bernardino Mountains 
Final 2003 AQMP 

2 - 10 

area recorded the greatest number of exceedances of the state standard (88 days), federal 

standard (26 days) and health advisory level (12 days). 

Figure 2-5 shows the distribution of the number of days exceeding the federal standard 

for 8-hour average ozone concentration in the Basin for the year 2001. The number of 

exceedances of the 8-hour federal ozone standard was also lowest at the coastal areas, 

increasing to a peak in the Riverside-San Bernardino Valley and adjacent mountain areas. 
Chapter 2 Air Quality and Health Effects 

2 - 11 

FIGURE 2-4 

Ozone -2001 

Number of Days Exceeding the Federal Standard 

(1-hour average ozone > 0.12 ppm) 

FIGURE 2-5 

Ozone -2001 

Number of Days Exceeding the Federal Standard 

(8-hour average ozone > 0.08 ppm) 
Final 2003 AQMP 

2 - 12 

Carbon Monoxide (CO) Specific Information 

Health Effects

Individuals with a deficient blood supply to the heart are the most susceptible to the 

adverse effects of CO exposure. The effects observed include earlier onset of chest pain 

with exercise, and electrocardiograph changes indicative of worsening oxygen supply to 

the heart. 

Inhaled CO has no direct toxic effect on the lungs, but exerts its effect on tissues by 

interfering with oxygen transport by competing with oxygen to combine with 

hemoglobin present in the blood to form carboxyhemoglobin (COHb). Hence, conditions 

with an increased demand for oxygen supply can be adversely affected by exposure to 

CO. Individuals most at risk include patients with diseases involving heart and blood 

vessels, fetuses (unborn babies), and patients with chronic hypoxemia (oxygen 

deficiency) as seen in high altitudes. 

Reduction in birth weight and impaired neurobehavioral development has been observed 

in animals chronically exposed to CO resulting in COHb levels similar to those observed 

in smokers. Recent studies have found increased risks for adverse birth outcomes with 

exposure to elevated CO levels. These include pre-term births and heart abnormalities. 

Additional research is needed to confirm these results. 

Air Quality

Carbon monoxide concentrations were measured at 23 locations in the Basin and 

neighboring SSAB areas in 2001. Table 2-4 shows the 2001 maximum 8-hour average 

concentrations of carbon monoxide by air basin and county. 

Figure 2-6 shows the distribution of the maximum 8-hour average carbon monoxide 

concentrations in the Basin in 2001. Higher concentrations were limited to the areas of 

Los Angeles County where vehicular traffic is most dense, with the maximum 

concentration (7.71 ppm) recorded in the South Central Los Angeles County area. The 

Basin recorded the 6th highest maximum 8-hour average carbon monoxide concentration 

in the nation in 2001 and is one of the few areas in the country still designated as 

nonattainment for carbon monoxide. 
Chapter 2 Air Quality and Health Effects 

2 - 13 

TABLE 2-4 

2001 Maximum Carbon Monoxide Concentrations by Basin and County 

Basin/County 

Maximum 

8-Hr Avg. 

ppm 

Percent of 

Federal 

Standard 

Area 

South Coast Air Basin 

Los Angeles 7.7 81 South Central L.A. County 

Orange 4.7 49 Central Orange County, 

 North Orange County 

Riverside 4.5 47 Metropolitan Riverside County 

San Bernardino 3.3 35 Central San Bernardino Valley 

Salton Sea Air Basin 

Riverside 1.5 16 Coachella Valley 

FIGURE 2-6 

Carbon Monoxide - 2001 

Maximum 8-Hour Average Concentration, ppm 

(Federal Standard = 8-hour average CO > 9 ppm) 
Final 2003 AQMP 

2 - 14 

Particulate Matter (PM10 and PM2.5) Specific Information 

Health Effects

A consistent correlation between elevated ambient fine particulate matter (PM10 and 

PM2.5) levels and an increase in mortality rates, respiratory infections, number and 

severity of asthma attacks and the number of hospital admissions has been observed in 

different parts of the United States and various areas around the world. In recent years, 

some studies have reported an association between long-term exposure to air pollution 

dominated by fine particles and increased mortality, reduction in life-span, and an 

increased mortality from lung cancer. 

Daily fluctuations in fine particulate matter concentration levels have also been related to 

hospital admissions for acute respiratory conditions in children, to school and 

kindergarten absences, to a decrease in respiratory lung volumes in normal children and 

to increased medication use in children and adults with asthma. Recent studies show 

lung function growth in children is reduced with long-term exposure to particulate matter. 

The elderly, people with pre-existing respiratory and/or cardiovascular disease and 

children appear to be more susceptible to the effects of PM10 and PM2.5. 

Air Quality, PM10

The South Coast Air Quality Management District monitored PM10 concentrations at 18 

locations in 2001. Maximum 24-hour and annual average concentrations are shown in 

Tables 2-5 and 2-6. 

Higher concentrations associated with high winds in the desert areas were recorded in the 

Coachella Valley area of Salton Sea Air Basin. The data for samples collected on these 

high-wind days were excluded in accordance with U.S. EPA's Natural Event Policy. 

Figure 2-7 shows the 2001 annual average PM10 concentrations in different areas of the 

Basin. The federal annual PM10 standard was exceeded at only a few locations in the 

District in the areas of Riverside and San Bernardino Counties in and around the 

Metropolitan Riverside County area and further inland in San Bernardino Valley areas. 

The federal 24-hour standard was also exceeded at two locations in Riverside and San 

Bernardino counties. The much more stringent state standards were exceeded in all areas 

of the Basin monitored in 2001. 
Chapter 2 Air Quality and Health Effects 

2 - 15 

TABLE 2-5 

2001 Maximum 24-hour Average PM10 Concentrations by Basin and County 

Basin/County 

Maximum 

24-Hr Avg.

μg/m3

Percent of 

Federal 

Standard 

Area 

South Coast Air Basin 

Los Angeles 106 70 East San Gabriel Valley 

Orange 93 62 Central Orange County 

Riverside 219 146 Banning Airport 

San Bernardino 166 110 Southwest San Bernardino Valley 

Salton Sea Air Basin 

Riverside* 149* 99* Coachella Valley 

*Adjusted for high-wind days in accordance with U.S. EPA's Natural Event Policy.

TABLE 2-6 

2001 Maximum Annual Average PM10 Concentrations by Basin and County 

Basin/County 

Annual 

Average 

μg/m3

Percent of 

Federal 

Standard 

Area 

South Coast Air Basin 

Los Angeles 45.3 90 East San Gabriel Valley 

Orange 36.0 79 Central Orange County 

Riverside 63.1 125 Metropolitan Riverside County 

San Bernardino 52.4 104 Southwest San Bernardino Valley 

Salton Sea Air Basin 

Riverside* 50.2* 99* Coachella Valley 

*Adjusted for the high-wind days in accordance with U.S. EPA's Natural Event Policy.

Air Quality, PM2.5

The South Coast Air Quality Management District began regular monitoring of PM2.5 in 

1999 following the EPA's adoption of the national PM2.5 standards in 1997. In 2001, 

PM2.5 concentrations were monitored at 18 locations throughout the District. Maximum 

24-hour and annual average concentrations are shown in Tables 2-7 and 2-8. Both 24-

hour and annual PM2.5 standards were exceeded at most locations in the Basin. 
Final 2003 AQMP 

2 - 16 

TABLE 2-7 

2001 Maximum 24-hour Average PM2.5 Concentrations by Basin and County 

Basin/County 

Maximum 

24-Hr Avg.

μg/m3

Percent of 

Federal 

Standard 

Area 

South Coast Air Basin 

Los Angeles 94.7 145 East San Fernando Valley 

Orange 70.8 108 Central Orange County 

Riverside 98.0 150 Metropolitan Riverside County 

San Bernardino 78.5 120 Central San Bernardino Valley 

Salton Sea Air Basin 

Riverside 44.7 68 Coachella Valley 

TABLE 2-8 

2001 Maximum Annual Average PM2.5 Concentrations by Basin and County 

Basin/County 

Annual 

Average 

μg/m3

Percent of 

Federal 

Standard 

Area 

South Coast Air Basin 

Los Angeles 26.1 168 South San Gabriel Valley 

Orange 22.4 145 Central Orange County 

Riverside 31.1 201 Metropolitan Riverside County 

San Bernardino 26.2 169 Southwest San Bernardino Valley, 

 Central San Bernardino Valley 

Salton Sea Air Basin 

Riverside 12.2 79 Coachella Valley 

Figure 2-8 shows the distribution of annual average PM2.5 concentrations in different 

areas of the Basin. Similar to PM10 concentrations, PM2.5 concentrations were higher in 

the inland valley areas of San Bernardino and Metropolitan Riverside counties. 

However, PM2.5 concentrations were also high in Los Angeles county and central 

Orange county. The high PM2.5 concentrations in Los Angeles and Orange counties are 

due to the secondary formation of smaller particulates resulting from mobile and 

stationary source activities. In contrast to PM10, PM2.5 concentrations were low in the 

Coachella Valley area of SSAB. PM10 concentrations are normally higher in the desert 

areas due to windblown and fugitive dust emissions. 
Chapter 2 Air Quality and Health Effects 

2 - 17 

FIGURE 2-7 

PM10 - 2001 

Annual Average Concentration Compared to Federal Standard 

(Federal standard = 50 μg/m3

, annual arithmetic mean) 

FIGURE 2-8 

PM2.5 - 2001 

Annual Average Concentration Compared to Federal Standard 

(Federal standard = 15 μg/m3

, annual arithmetic mean) 
Final 2003 AQMP 

2 - 18 

Nitrogen Dioxide (NO2) Specific Information 

Health Effects

Population-based studies suggest that an increase in acute respiratory illness, including 

infections and respiratory symptoms in children (not infants), is associated with longterm exposures to NO2 at levels found in homes with gas stoves, which are higher than 

ambient levels found in Southern California. Increase in resistance to air flow and airway 

contraction is observed after short-term exposure to NO2 in healthy subjects. Larger 

decreases in lung functions are observed in individuals with asthma and/or chronic 

obstructive pulmonary disease (e.g., chronic bronchitis, emphysema) than in healthy 

individuals, indicating a greater susceptibility of these sub-groups. 

In animals, exposure to levels of NO2 considerably higher than ambient concentrations 

results in increased susceptibility to infections, possibly due to the observed changes in 

cells involved in maintaining immune functions. The severity of lung tissue damage 

associated with high levels of ozone exposure increases when animals are exposed to a 

combination of ozone and NO2. 

Air Quality

In 2001, nitrogen dioxide concentrations were monitored at 23 locations. No area of the 

Basin or SSAB exceeded the federal or state standards for nitrogen dioxide. Maximum 

annual average concentrations for 2001 are shown in Table 2-9. The Basin has not 

exceeded the federal standard for nitrogen dioxide since 1991, when the Los Angeles 

County portion of the Basin recorded the last exceedance of the standard in any U.S. 

county. 

The state standard was not exceeded at any District monitoring location in 2001. The 

highest 1-hour average concentration recorded (0.25 ppm in East San Fernando Valley) 

was 96 percent of the state standard. 
Chapter 2 Air Quality and Health Effects 

2 - 19 

TABLE 2-9 

2001 Maximum Nitrogen Dioxide Concentrations by Basin and County 

Basin/County 

Maximum 

Annual Avg. 

ppm 

Percent of 

Federal 

Standard 

Area 

South Coast Air Basin 

Los Angeles 0.0419 78 East San Fernando Valley 

Orange 0.0293 55 Central Orange County 

Riverside 0.0247 46 Metropolitan Riverside County 

San Bernardino 0.0384 72 Northwest San Bernardino 

Valley 

Salton Sea Air Basin 

Riverside 0.0175 33 Coachella Valley 

Sulfur Dioxide (SO2) Specific Information 

Health Effects

Exposure of a few minutes to low levels of SO2 can result in airway constriction in some 

asthmatics. All asthmatics are sensitive to the effects of SO2. In asthmatics, increase in 

resistance to air flow, as well as reduction in breathing capacity leading to severe 

breathing difficulties, are observed after acute exposure to SO2. In contrast, healthy 

individuals do not exhibit similar acute responses even after exposure to higher 

concentrations of SO2. 

Animal studies suggest that despite SO2 being a respiratory irritant, it does not cause 

substantial lung injury at ambient concentrations. However, very high levels of exposure 

can cause lung edema (fluid accumulation), lung tissue damage, and sloughing off of 

cells lining the respiratory tract. 

Some population-based studies indicate that the mortality and morbidity effects 

associated with fine particles show a similar association with ambient SO2 levels. In 

these studies, efforts to separate the effects of SO2 from those of fine particles have not 

been successful. It is not clear whether the two pollutants act synergistically or one 

pollutant alone is the predominant factor. 

Air Quality

No exceedances of federal or state standards for sulfur dioxide occurred in 2001 at any of 

the nine District locations monitored. Though sulfur dioxide concentrations remain well 
Final 2003 AQMP 

2 - 20 

below the standards, sulfur dioxide is a precursor to sulfate, which is a component of fine 

particulate matter, PM10 and PM2.5. Standards for PM10 and PM2.5 were both 

exceeded in 2001. Maximum concentrations of sulfur dioxide for 2001 are shown in 

Table 2-10. Sulfur dioxide was not measured at SSAB sites in 2001. Historical 

measurements showed concentrations to be well below standards and monitoring has 

been discontinued. 

TABLE 2-10 

2001 Maximum Sulfur Dioxide Concentrations by Basin and County 

Basin/County 

Maximum 

24-hr Avg. 

ppm 

Percent of 

Federal 

Standard 

Area 

South Coast Air Basin 

Los Angeles 0.012 8 Southwest Coastal Los Angeles County, 

 South Coastal Los Angeles County 

Orange 0.007 5 North Coastal Orange County 

Riverside 0.011 8 Metropolitan Riverside County 

San Bernardino 0.010 7 Central San Bernardino Valley 

Salton Sea Air Basin 

Riverside N.D. 

N.D. = No Data. Historical measurements indicate concentrations are well below standards. 

Sulfates (SO4

=

) Specific Information 

Health Effects

Most of the health effects associated with fine particles and sulfur dioxide at ambient 

levels are also associated with sulfates. Thus, both mortality and morbidity effects have 

been observed with an increase in ambient sulfate concentrations. However, efforts to 

separate the effects of sulfates from the effects of other pollutants have generally not been 

successful. 

Clinical studies of asthmatics exposed to sulfuric acid suggest that adolescent asthmatics 

are possibly a subgroup susceptible to acid aerosol exposure. Animal studies suggest that 

acidic particles such as sulfuric acid aerosol and ammonium bisulfate are more toxic than 

non-acidic particles like ammonium sulfate. Whether the effects are attributable to 

acidity or to particles remains unresolved. 
Chapter 2 Air Quality and Health Effects 

2 - 21 

Air Quality

In 2001, the state sulfate standard was not exceeded anywhere in the Basin. Maximum 

concentrations by air basin and county are shown in Table 2-11. No sulfate data were 

obtained at SSAB stations in 2001. Historical sulfate data showed concentrations in the 

SSAB areas to be well below the standard, and measurements have been discontinued. 

TABLE 2-11 

2001 Maximum Sulfate Concentrations by Basin and County 

Basin/County 

Maximum

24-hr Avg.

μg/m3

Percent of 

Federal 

Standard 

Area 

South Coast Air Basin 

Los Angeles 20.6 82 Southwest Coastal Los Angeles County

Orange N.D. 

Riverside 10.7 43 Metropolitan Riverside Co. 

San Bernardino 11.5 46 Central San Bernardino Valley 

Salton Sea Air Basin 

Riverside N.D. 

N.D. = No Data. Historical measurements indicate concentrations are well below standards. 

Lead (Pb) Specific Information 

Health Effects

Fetuses, infants, and children are more sensitive than others to the adverse effects of lead 

exposure. Exposure to low levels of lead can adversely affect the development and 

function of the central nervous system, leading to learning disorders, distractibility, 

inability to follow simple commands, and lower intelligence quotient. In adults, 

increased lead levels are associated with increased blood pressure. 

Lead poisoning can cause anemia, lethargy, seizures and death. It appears that there are 

no direct effects of lead on the respiratory system. Lead can be stored in the bone from 

early-age environmental exposure, and elevated blood lead levels can occur due to 

breakdown of bone tissue during pregnancy, hyperthyroidism (increased secretion of 

hormones from the thyroid gland) and osteoporosis (breakdown of bony tissue). Fetuses 

and breast-fed babies can be exposed to higher levels of lead because of previous 

environmental lead exposure of their mothers. 
Final 2003 AQMP 

2 - 22 

Air Quality

The federal and state standards for lead were not exceeded in any area of the District in 

2001. There have been no violations of the standards at the District’s regular air 

monitoring stations since 1982, as a result of removal of lead from gasoline. However, 

special monitoring stations immediately adjacent to stationary sources of lead have 

recorded exceedances of the standards in very localized areas of the Basin as recently as 

1991 for the federal standard and 1994 for the state standard. Table 2-12 shows the 

maximum concentrations recorded in 2001. The highest quarterly average lead 

concentration (0.49 μg/m3 in Central Los Angeles), measured at special monitoring sites 

immediately adjacent to stationary sources of lead, was 32 percent of the federal 

standard. 

The maximum monthly average lead concentration at the regular monitoring stations 

(0.23 μg/m3

 in the South Central Los Angeles County area) was 15 percent of the state 

standard. The maximum at the special monitoring sites immediately adjacent to sources 

(0.57 μg/m3

 in Central Los Angeles) was 38 percent of the standard. 

TABLE 2-12 

2001 Maximum Lead Concentrations by Basin and County 

Basin/County 

Maximum 

Quarterly 

Average 

μg/m3

Percent of 

Federal 

Standard 

Area 

South Coast Air Basin 

Los Angeles 0.12 8 South Central Los Angeles County 

Orange N.D. 

Riverside 0.03 2 Metropolitan Riverside County 

San Bernardino 0.04 3 Northwest San Bernardino Valley, 

 Central San Bernardino Valley 

Salton Sea Air Basin 

Riverside N.D. 

N.D. = No Data. Historical measurements indicate concentrations are well below standards. 

Summary 

In 2001, the Basin exceeded federal and state standards for ozone, PM10 and PM2.5. 

The Salton Sea Air Basin areas continued to exceed standards for ozone and PM10. 

The Basin exceeded one or more federal standards on 58 days. Maximum concentrations 

of PM2.5 exceeded the federal standard by the widest margin. Ozone and PM10 
Chapter 2 Air Quality and Health Effects 

2 - 23 

concentrations exceeded the federal standards by a smaller margin. In 2001, for the first 

time since its monitoring, carbon monoxide concentration did not exceed the standards 

anywhere in the Basin. Maximum concentrations for nitrogen dioxide, sulfur dioxide 

sulfate and lead continued to remain below the state and federal standards.