CHAPTER 10 

LOOKING BEYOND CURRENT REQUIREMENTS 

Introduction 

Uncertainties Associated with the Technical Analysis 

A First Look at the Year 2020 Ozone Air Quality 

New Federal Air Quality Standards for Ozone and Fine Particulates 

New State PM Air Quality Standards 
Chapter 10 Looking Beyond Current Requirements 

10 - 1 

INTRODUCTION 

This Chapter presents additional analyses which are not required under law to be 

included in the AQMP, but are presented here for informational purposes because they 

have significant future implications to the region’s ability to reach clean air. Specifically 

this chapter discusses uncertainties associated with the technical analysis provided in the 

AQMP; provides a first look at the year 2020; and lastly, offers a preliminary analysis 

regarding the new federal PM2.5 and 8-hour ozone ambient air quality standards. 

UNCERTAINTIES ASSOCIATED WITH THE TECHNICAL ANALYSIS 

As with any plan update there are uncertainties associated with the technical analysis. 

The following paragraphs describe the primary contributors to such uncertainties as well 

as some of the safeguards build-in to the air quality planning process to manage and 

control such uncertainties. 

Demographic and Growth Projections

Uncertainties exist in the demographic and growth projections for the future base years. 

As projections are made to longer periods (i.e., over ten or more years), the uncertainty 

of the projections become greater. Examples of activities that may contribute to these 

types of uncertainties include the rate and the type of new sources locating in the Basin 

and their geographic distribution, future year residential construction, military base reuse 

and their air quality impact, and economic prosperity. 

Input Elements to Air Quality Models

In addition to the above, there are also uncertainties in the technical information 

gathered for the air quality analysis. There are three major input elements associated 

with any air quality modeling analysis: ambient air quality monitoring data; 

meteorological measurements; and emissions inventory. All three input elements have 

various levels of uncertainties impacting the technical analysis. 

Ambient Air Quality Monitoring Data

Generally, ambient air quality measurements are within plus or minus half of a unit of 

measurement (e.g., for ozone usually reported in units of pphm would be accurate to 

within ±0.5 pphm). Due to this uncertainty, the Basin’s ozone attainment status based 

on ambient monitoring data would be achieved if all ozone monitors reported ozone 

concentration levels less than or equal to 12.4 pphm. 
Final 2003 AQMP 

10 - 2 

Meteorological Measurements

Air Quality models have to rely on reliable meteorological input data to accurately 

simulate future ambient concentration levels. There are uncertainties associated with 

meteorological measurements and model input parameters, such as averaging of 

instantaneous wind speeds and directions to hourly averaged values, and directional 

consistency during low (stagnant) wind conditions. 

Emissions Inventory

As discussed in Chapter 3, large uncertainties in the mobile source emissions inventory 

estimates have been observed as evident with the latest EMFAC2002 release. On-road 

mobile source emission estimates have increased with each new EMFAC release. Onroad mobile source emissions have inherent uncertainties also with the current 

methodologies used to estimate vehicle activity such as vehicle miles traveled. 

Stationary (or point) source emission estimates have less associated uncertainties 

compared to area source emission estimates. Major stationary sources report emissions 

annually whereas area source emissions are, in general, estimated based on production or 

usage information. Area source emissions including paved road dust and fugitive dust 

have significant uncertainties in the estimation of particulate (PM10) emissions due to 

the methodologies used for estimation, temporal loading and weather impacts. 

Air Quality Models

The air quality models used for ozone and particulate air quality analysis are 

sophisticated, complex 3-dimensional models that utilize 3-dimensional meteorological 

models, complex chemical mechanisms that accurately simulate ambient reactions of 

pollutants and sophisticated numerical methods to solve complex mathematical 

equations that lead to the prediction of ambient air quality concentrations. There are 

uncertainties with the development of the meteorological data input to the 3-dimentional 

meteorological models, such as the estimation of 3-dimensional wind fields from a 

limited number of meteorological measurements collected at various locations 

throughout the Basin. While air quality models progressively became more 

sophisticated in employing improved chemical reaction modules that more accurately 

simulate the complex ambient chemical reaction mechanisms of the various pollutants, 

such improved modules are still based on limited experimental data which carry 

associated uncertainties. In order to predict ambient air quality concentrations, air 

quality models rely on the application of sophisticated numerical methods to solve 

complex mathematical equations that govern the highly complex physical and chemical 

processes that also have associated uncertainties. 
Chapter 10 Looking Beyond Current Requirements 

10 - 3 

Are There Any Safeguards Against Uncertainties? 

Yes. While completely eliminating uncertainties is an impossible task, there are a 

number of features and practices build-into the air quality planning process that manage 

and control such uncertainties and preserve the integrity of an air quality management 

plan. 

It should be noted that uncertainties run in two directions and comparisons with recent 

year projections show that the air quality is improving at a greater rate than was 

projected. This would indicate that uncertainties have not significantly affected the 

integrity of the Plan to date. 

Furthermore, the concerns regarding uncertainties in the technical analysis are reduced 

with future AQMP revisions. Each AQMP revision employs the best available technical 

information available. Under state law, the AQMP revision process is a dynamic 

process with revisions occurring every three years. The AQMP revision represents a 

“snapshot in time” providing the progress achieved since the previous AQMP revision 

and efforts still needed in order to attain air quality standards. 

Under the federal Clean Air Act, a state implementation plan (SIP) is prepared for each 

criteria pollutant. The SIP is not updated on a routine basis under the federal Clean Air 

Act. However, the federal Clean Air Act recognizes that uncertainties do exist and 

provides safeguards if a nonattainment area does not meet an applicable milestone or 

attain federal air quality standards by their applicable dates. Contingency (or backstop) 

measures are required in the AQMP and must be developed into regulations such that 

they will take effect if a nonattainment area does not meet an applicable milestone or 

attainment date. In addition, federal sanctions may be imposed until an area meets 

applicable milestone targets. 

In 1996, U.S. EPA released an updated guidance document on the use of modeled results 

to demonstrate attainment of the federal ozone air quality standard1

 The guidance 

document recognized that there will be uncertainties with ozone modeling analysis. For 

severe and extreme ozone nonattainment areas, the U.S. EPA recommends that at least 

one “mid-course” review of air quality, emissions and modeled data be conducted. A 

second review, shortly before the attainment date, should be conducted also. Such 

actions will occur in the South Coast Air Quality Management District. 

 

1

 U.S. EPA, Guidance on Use of Modeled Results to Demonstrate Attainment of the Ozone NAAQS, EPA454/B-95-007, June 1996
Final 2003 AQMP 

10 - 4 

A FIRST LOOK AT THE YEAR 2020 OZONE AIR QUALITY 

With continued growth in the South Coast Air Basin beyond 2010, concerns have been 

raised whether the South Coast Air Basin can maintain the federal ozone air quality 

standard. As such, an ozone air quality analysis for 2020 was performed. Data on the 

projected growth in the Basin and surrounding areas were provided by SCAG. 

The future year (2020) ozone air quality projections suggest that additional emissions 

reductions will be required to offset growth to maintain the 1-hour ozone standard and 

attain the 8-hour ozone standard. Mobile source emissions projections through 2020 

indicate that continued reductions in VOC and NOx will occur as newer vehiles are 

introduced. NOx reductions will be most significant between 2010 and 2020 with VOC 

reductions having a smaller role. Growth in the area source category will act to offset 

the mobile source VOC reductions by 2020 to reverse the trend of lowering ambient 

ozone concentrations. 

NEW FEDERAL AIR QUALITY STANDARDS FOR OZONE AND FINE 

PARTICULATES 

In July 1997, U.S. EPA promulgated new national ambient air quality standards for 

ozone and particulate matter. 

As part of the requirements of the CAA, every five years the U.S. EPA must review the 

ambient air quality standards and propose revisions, if necessary, to “protect public 

health with an adequate margin of safety,” based on the latest, best-available science. 

This review process includes a comprehensive evaluation of the latest health studies; a 

redrafting, if appropriate, of the relevant pollutant criteria document; and a staff report 

recommending the position of the U.S. EPA staff relative to the air quality standards. 

Further, these documents and U.S. EPA staff recommendation are reviewed by a panel 

of independent experts authorized by the CAA, the Clean Air Science Advisory 

Committee (CASAC). 

In promulgating the new standards, U.S. EPA followed the elaborate review process 

described above, which took several years to complete. The evaluation of thousands of 

peer-reviewed scientific studies led to the conclusion that existing standards for the two 

pollutants, ozone and particulates, were not adequately protective of public health and 

resulted in the promulgation of the new standards. The studies indicated that for ozone, 

longer exposures at levels below the existing 1-hour standard were found to cause 

significant health effects, including asthma attacks, breathing and respiratory problems, 

loss of lung function, and possible long-term lung damage and lowered immunity to 

disease. With respect to particulate matter, the studies indicated that exposure to 
Chapter 10 Looking Beyond Current Requirements 

10 - 5 

particles smaller than those that were being regulated by U.S. EPA were found to lodge 

deeply in the lungs and cause premature deaths and respiratory problems. 

On June 2, 2003, EPA published in the Federal Register its “Proposed Rule to 

Implement the 8-Hour Ozone National Ambient Air Quality Standard,” 68 Fed.Reg. 

32801-32870. As part of that proposal, EPA solicits comment on a proposal to revoke 

the present 1-hour ozone standard either in whole or in part one year after EPA 

designates the 8-hour ozone nonattainment areas. (68 Fed.Reg. 32019.) It is expected 

that EPA will designate the 8-hour ozone nonattainment areas by April 15, 2004. (68 

Fed.Reg. 32808.) EPA is extremely unlikely to finalize this rule before the 2003 AQMP 

is adopted and submitted to EPA. At present, it is uncertain whether, when, or to what 

extent EPA will revoke the existing 1-hour ozone standard. Therefore, the 2003 AQMP 

assumes the 1-hour ozone standard will remain in effect for the foreseeable future. 

What are the Health Concerns? 

A brief summary of the effects associated with these pollutant exposures at levels 

observable in Southern California is presented. A more detailed discussion of health 

effects is provided in Appendix I. 

Ozone

People exercising outdoors, children and persons with preexisting lung disease such as 

asthma are considered to be susceptible sub-groups for ozone effects. Identified in 

human and/or animal studies with varying exposure duration the adverse health effects 

which are either induced by ozone or associated with ambient ozone exposures include: 

breathing pattern changes; reduction in breathing capacity and exercise performance; 

increase in airway resistance; susceptibility to infections; excess hospital admissions and 

emergency room visits; and acute inflammation of the respiratory tract including some 

cellular changes. 

The lowest range of ozone exposure within which lung functional changes (decrease in 

breathing lung volumes and increase in airway resistance) are observed is 0.08 to 0.12 

ppm for 6-8 hours under moderate exercising conditions. Under similar exposure 

conditions, biochemical indicators of lung inflammation are induced in healthy adults 

exposed to ozone in the range of 0.08 to 0.10 ppm. Excess hospital admissions and 

emergency room visits are observed when hourly ozone concentrations are as low as 

0.08 to 0.10 ppm. Thus, the attainment of the current NAAQS (0.12 ppm) is not likely 

to prevent all the adverse effects indicated from ozone exposure. 
Final 2003 AQMP 

10 - 6 

Particulate Matter

The major categories of adverse health effects associated with PM10 include: increase in 

mortality associated with acute and chronic exposures; exacerbation of preexisting 

respiratory and cardiovascular diseases leading to an increase in hospital admissions and 

emergency room visits; school absences; work loss days and restricted activity days; 

changes in lung function and structure; and altered lung defense mechanisms. 

A review and statistical analysis of recent population studies published on acute adverse 

effects of PM10 indicates that an incremental increase of PM10 by 10 μg/m3

 can lead to 

a significant increase in both mortality and morbidity risks. The elderly, people with 

preexisting respiratory and/or cardiovascular disease(s) and children appear to be most 

susceptible to the effects of PM10. These findings suggest that even when an area meets 

the existing NAAQS for PM10 the community is likely to continue to have the adverse 

impact from ambient PM10 exposures. 

A limited number of studies which have employed both PM10 and PM2.5 indices for 

pollution suggest that the adverse effects show a better correlation with the latter. A 

growing consensus exists among the scientific community that the fine fraction of PM10 

is relatively more toxic than the coarse fraction and is responsible for the majority of 

PM10 effects observed. 

In addition, U.S. EPA in its recent PM10 NAAQS review has concluded that the 

difference in exposure relationships, and the strong likelihood of fine mode fraction of 

PM10 being significant contributors to PM-related health effects in sensitive 

populations, are sufficient to justify the consideration of fine and coarse mode particles 

in PM10 as separate classes of pollutants. Hence, U.S. EPA has recommended 

additional PM2.5 NAAQS. 

What is the New Federal Ozone Standard? 

As a result of this review, U.S. EPA is phasing out and replacing the current 1-hour 

primary ozone standard with a new 8-hour standard to protect against longer exposure 

periods. (Areas currently exceeding the federal 1-hour standard are still commited to 

demonstrating attainment in accordance with their scheduled date). The new ozone 

standard is set at a concentration of 0.08 parts per million (ppm) and represents a 

tightening of the existing 1-hour ozone standard which is set at 0.12 ppm. Under the 

form of the standard adopted by U.S. EPA, areas are allowed to disregard their three 

worst measurements every year and average their fourth highest measurements over 

three years to determine if they meet the standard. 
Chapter 10 Looking Beyond Current Requirements 

10 - 7 

What are the new Federal PM Standards? 

For particulate matter, U.S. EPA established a new annual and a 24-hour standard for the 

finest fraction of particulates, PM2.5 (particles less than 2.5 micrometers) to complement 

the existing PM10 standards. The new annual PM2.5 standard is set at 15 micrograms 

per cubic meter and the new 24-hour PM2.5 standard is set at 65 micrograms per cubic 

meter. The annual component of the standard was set to provide protection against 

typical day-to-day exposures as well as longer-term exposures, while the daily 

component protects against more extreme short-term events. For the new 24-hour PM2.5 

standard, the form of the standard is based on the 98th percentile of 24-hour PM2.5 

concentrations measured in a year (averaged over three years) at the monitoring site with 

the highest measured values in an area. This form of the standard will reduce the impact 

of a single high exposure event that may be due to unusual meteorological conditions 

and thus provide a more stable basis for effective control programs. 

While U.S. EPA has retained the current annual PM10 standard of 50 micrograms per 

cubic meter, it has modified the form of the 24-hour PM10 standard set at 150 

micrograms per cubic meter. More specifically, U.S. EPA revised the 1-expectedexceedance form of the current standard with a 99th percentile form, averaged over three 

years. 

Implementation of the New Federal Standards 

Although the promulgation of the new standards for ozone and fine particulates is 

complete, U.S. EPA has yet to promulgate the air quality designations of the various 

regions for the new ozone and PM2.5 standards. Under a consent decree that was 

reached in response to a lawsuit that was filed by several environmental groups, U.S. 

EPA has agreed to finalize its designations for the 8-hour ozone standard by 2004. In an 

effort to harmonize the implementation of both the 8-hour ozone and PM2.5 standards, 

the U.S. EPA will also attempt to complete its designations for the PM2.5 standard by 

the end of 2004. 

The state implementation plans that will incorporate attainment demonstrations with the 

new 8-hour and PM2.5 standards are expected to be required within three years of the air 

quality designations or by 2007. Therefore, the current regulatory control strategies will 

continue to focus on attaining the 1-hour ozone standard with the recognition that these 

controls will have benefits toward attaining the 8-hour ozone and PM2.5 standards. The 

U.S. EPA is considering several options in transitioning from the 1-hour to the 8-hour 

standard, while ensuring that no backsliding will occur. Based on the recent consent 

decree guidance, it is most likely that the Basin will have to meet the federal PM2.5 

standards by 2014 and the 8-hour ozone standard by 2021. 
Final 2003 AQMP 

10 - 8 

Assessment of the New Federal Standards 

Ozone 

The District has evaluated the differences between the current 1-hour standard and the 

new 8-hour standard for both 2001 (observed) and 2010 (predicted) ozone for this 

comparison. These differences are summarized in Table 10-1. Currently, the 1-hour 

standards are exceeded by 58 percent. The maximum 8-hour would exceed the new 

standard by 80 percent. Future year projections show that the 1-hour standard would be 

met in 2010, but the maximum 8-hour standard would still be exceeded by 35 percent. 

Because federal guidance has not yet been developed for modeling attainment 

demonstrations of a 4th highest value, a projection of the 4th highest 8-hour average 

ozone concentration cannot be made at this time. 

TABLE 10-1 

Comparison of Ozone Standards 

Observed 

Max 

Value 

(ppm)

% 

above

Std.

Predicted 

Max 

Value 

(ppm)

% 

above 

Std.

Predicted 

Max 

Value 

(ppm)

% 

above

Std

Option Standard 

(ppm) 

2001 2010 

Option-1 

2010 

Option-2 

1-hour 

(maximum) 0.12 0.190 58 0.123 Met 0.124 Met 

8-hour 

(maximum) 0.08 0.144 80 0.107 34 0.108 35 

8-hour 

(4th highest) 0.08 0.139 74 * * * * 

*Future-year federal guidance for attainment demonstration not available. 
Chapter 10 Looking Beyond Current Requirements 

10 - 9 

Particulate Matter

The annual average PM2.5 standard is set at 15 μg/m3

, and the 24-hour average PM2.5 

standard is set at 65 μg/m3. 

A comparison of the current PM10 standards and the new PM2.5 standards for 2001 and 

2006 are shown in Table 10-2. The 2001 values are derived from the measurements 

sampled through the routine Basin PM10 air monitoring. The 2006 PM2.5 values are 

estimated from the particulate modeling applications (discussed in Chapter 5 and 

Appendix V). Currently, the 24-hour average PM10 standard is exceeded by 46 percent. 

This maximum exceedance occurred under high-wind "Santa Ana" conditions. The 

annual standard is exceeded by 26 percent. Attainment for both PM10 standards can be 

demonstrated by 2006. 

For the new 24-hour average and annual standards, PM2.5 in 2001 will be exceeded by 

51 and 107 percent respectively. In 2006 the 24-hour average PM2.5 standard would be 

exceeded by 49 percent and the annual average standard would be exceeded 95 percent. 

For the 2010 Option-1 control strategy, the 24-hour average PM2.5 standard would be 

exceeded by 5 percent and the annual average PM2.5 is estimated to be exceeded by 80 

percent. The annual average PM2.5 for the Option-2 is expected to be approximately 81 

percent above the federal standard and the 24-hour average PM2.5 standard would be 

exceeded by 9 percent. For both control scenarios, the 2010 PM10 federal standard is 

expected to be met. 

It is also important in looking into the future to understand the significant components of 

PM2.5 as projected for the year 2006. These are shown in Figure 10-1. The ammonium 

and nitrate portions represent the dominant fraction of PM2.5 on both an annual and 

episodic (24-hour) basis. Note, too, that the crustal component, as identified within the 

category labeled “others,” and which represents a significant fraction of PM10, plays a 

very small role in the PM2.5 picture. For the 24-hour standard, it is evident that 

significant reductions in ammonium nitrate will be needed over and above the current 

PM10 control strategy in order to attain a possible PM2.5 standard. Appreciable 

reductions will also be needed for both organic and elemental carbon, the former from 

VOC emissions and the latter from soot emissions, primarily from diesel exhaust. 
Final 2003 AQMP 

10 - 10 

TABLE 10-2 

Comparison of Particulate Matter Standard 

Observed 

Max 

Value 

(μg/m3

)

% 

above

Std.

Predicted 

Max 

Value 

(μg/m3

)

% 

above

Std

Predicted 

Max 

Value 

(μg/m3

)

% 

above 

Std

Predicted 

Max 

Value 

(μg/m3

) 

% 

above

Std 

Option Standard 

(μg/m3

) 

2001 2006 2010 Option-1 2010 Option-2 

Current 

PM10

(24-hour) 

150 219* 46 150 Met 133 Met 137 Met 

Current 

PM10

(Annual) 

50 63 26 49 Met 45 Met 46 Met 

New 

PM2.5

(24-hour) 

65 98 51 97 49 68 5 71 9 

New 

PM2.5

(Annual) 

15 31 107 29 95 27 80 27 81 

* The 24-hour Basin maximum average of 219 (μg/m3) occurred under high wind conditions 

And reflect the contributions of fugitive wind blown dust. 

NEW STATE PM AIR QUALITY STANDARDS 

On June 2002, CARB also adopted new, stricter standards for particulate matter that would 

affect both the corse as well as fine particulate fraction. The newly adopted standards 

reduced the PM10 annual average standard from 30 microgram per cubic meter to 20 

micrograms per cubic meter and retained the 24-hour PM10 standard of 50 micrograms per 

cubic meter. The new PM2.5 annual average standard was set at 12 micrograms per cubic 

meter. In addition, CARB also revised the monitoring methods for these standards, and 

delayed action on the proposed 24-hour PM2.5 standard in light of the recent findings related 

to statistical issues in several key short-term exposure health effects studies. Obviously, 

achieving these standards poses an even greater challenge than meeting the new federal 8-

hour ozone and PM2.5 standards. 
Chapter 10 Looking Beyond Current Requirements 

10 - 11 

FIGURE 10-1 

Estimated PM2.5 Components in 2006 

(a) Predicted Annual Average

(29 ug/m3)

10%

30%

13%

15%

8%

24%

SO4

NO3

NH4

OC

EC

Others

(b) Predicted Maximum 24-Hour

Average (97 ug/m3)

5%

53%

17%

17%

8%

0%

SO4

NO3

NH4

OC

EC

Others