2.0 Introduction
2.1. Purpose
2.2. Background
2.2.1. Clean Air Act of 1990
2.2.2. Ozone
Ozone is produced in complex chemical reactions when its precursors, oxides of
nitrogen (NOx) and volatile organic compounds (VOCs), react in the presence of
sunlight. Ozone that is found high in the earth's upper atmosphere (stratosphere) is
beneficial because it inhibits the penetration of the sun’s harmful ultraviolet rays to the
ground. However, ozone can also form near the earth's surface (troposphere). This
ozone, commonly referred to as ground-level ozone, is breathed in by or comes into
contact with people, animals, crops and other vegetation, and can cause a variety of
serious health effects.
Complicating the formation of ground-level ozone is the fact that the chemical reactions
that create ozone can take place while the pollutants are being blown through the air
(transported) by the wind. This means that elevated levels of ozone can occur many
miles away from the source of their original precursor emissions. Therefore, unlike
more traditional pollutants, e.g., sulfur dioxide and lead, which are emitted directly and
can be controlled at their source, reducing ozone concentrations poses additional
control challenges. To help states address the issues of ozone transport, the Clean Air
Act (CAA) established the Ozone Transport Commission1 (OTC) for the states from
Maine to Virginia, and the District of Columbia.
2.2.3. Ozone Precursor - Oxides of Nitrogen
Oxides of Nitrogen are a group of gases including nitrogen oxide (NO) and nitrogen
dioxide (NO2). Although most NOx is emitted as NO it is readily converted to NO2 in the
atmosphere. NO2 is a reddish-brown, highly reactive gas. When NO2 reacts with other
chemicals in the atmosphere, it not only results in the formation of ozone, but also
particulate matter, haze and acid rain.
1
42 U.S.C. §7511c(a)
Sources of NO and NO2 include motor vehicle exhaust (including both gasoline-fueled
vehicles and heavy-duty diesel vehicles), the burning of coal, oil or natural gas, and
industrial processes such as welding, electroplating and dynamite blasting. Figure __
shows the national breakdown of NOx emissions by category. In this chart, fuel
combustion refers to stationary sources (i.e, power plants).
Figure ??: NOx Emissions by Source Category, 2002
Micellaneous
Fuel Combustion
Transportation
Industrial Processes
Source: USEPA National Air Quality
Emissions Trends Report, 2003
Special Studies Edition, September
2003.
Since much of the NOx in the air is emitted by motor vehicles, concentrations tend to
peak during the morning and afternoon rush hours. Also, due in part to poorer local
dispersion conditions caused by light winds and other weather conditions that are more
prevalent in the colder months of the year, NOx concentrations tend to be higher in the
winter than the summer.
2.2.4. Ozone Precursor - Volatile Organic Compounds
Volatile organic compounds are chemicals that evaporate (or volatilize) when they are
exposed to air. They are called organic because they contain carbon. Some VOC
compounds are highly reactive and have a short atmospheric lifespan, while others are
not as reactive and can have a very long lifespan. The short-lived compounds contribute
substantially to atmospheric photochemical reactions and thus the formation of ozone.
Volatile organic compounds are used in the manufacture of, or are present in, many
products used daily in both homes and businesses, such as fuels (gasoline and heating
oil), common household items like polishes, cosmetics, perfumes and cleansers,
industrial items like degreasers and solvents, and in office products like correction fluid,
magic markers, paper, rubber bands, and invisible tape. The names of many VOCs
may be familiar: carbon tetrachloride, trichloroethene, tetrachloroethene,
2
trichloroethane, benzene and toluene. Because of their widespread historical use, and
past lack of stringent disposal requirements, they are in our air, soil, and water in
varying concentrations.
Figure __ shows the national breakdown of VOC emissions by category. As with the
NOx chart, fuel combustion refers to stationary sources (i.e, power plants).
Figure ??: Anthropogenic VOC Emissions
by Source Category, 2002
Miscellaneous
Fuel Combustion
Transportation
Industrial Processes
Note: Sums do not equal
100 due to rounding
Source: USEPA National
Air Quality Emissions
Trends Report, 2003
Special Studies Edition,
September 2003.
2.2.5. Impacts of Ozone Exposure
Ground-level ozone can irritate lung airways and cause inflammation much like
sunburn. Other symptoms from exposure include wheezing, coughing, pain when
taking a deep breath, and breathing difficulties during exercise or outdoor activities.
Even at very low levels, exposure to ground-level ozone can result in decreased lung
function, primarily in children active outdoors, as well as increased hospital admissions
and emergency room visits for respiratory illnesses among children and adults with preexisting respiratory diseases (i.e. asthma). In addition to these primary symptoms,
medical professionals now believe that repeated exposure to ozone pollution for several
months could cause permanent lung damage.2 People with respiratory problems are
most vulnerable to the health effects associated with ozone exposure, but even healthy
people that are active outdoors can be affected when ozone levels are high.
2
Need reference
3
In addition to its health effects, ozone interferes with a plant’s ability to produce and
store nutrients, which makes them more susceptible to disease, insects, other
pollutants, and harsh weather. This impacts annual crop production throughout the
United States, resulting in significant losses, and injures native vegetation and
ecosystems. In addition, ozone damages the leaves of trees and other plants, ruining
the appearance of cities, national parks, and recreation areas. Ozone can also damage
certain man-made materials, such as textile fibers, dyes, and paints.
2.3. 8-Hour Ozone Standard
Due to the severity of the health and welfare effects associated with ground-level ozone,
the CAA required the United States Environmental Protection Agency (USEPA) to
establish National Ambient Air Quality Standards (NAAQS) designed to protect public
health and the environment. The CAA allows the USEPA to establish two types of
national air quality standards for primary air pollutants. The primary standards set limits
to protect public health, including the health of "sensitive" populations such as
asthmatics, children, and the elderly. The secondary standards set limits to protect
public welfare, including protection against decreased visibility, damage to animals,
crops, vegetation, and buildings. Up until recently, there was only one set of ozone
NAAQS, established as 0.12 parts per million (ppm) over a 1-hour average for both the
primary and secondary standards. The ___ of ___ was designated as ____for the 1hour ozone standard.
On July 16, 1997, the USEPA promulgated a new set of NAAQS for ozone. As with the
1-hour ozone standards, the primary and secondary standards are identical. The new
standards established a limit of 0.08 ppm over an 8-hour average for both the primary
and secondary standards. As part of its Phase I final rule to implement the 8-hour
ozone NAAQS3, the USEPA determined to revoke the 1-hour ozone standard in full,
including the associated designations and classifications, 1 year following the effective
date of the designations for the 8-hour NAAQS. All 8-hour ozone designations were
effective on June 15, 2004. Therefore, the 1-hour ozone standard was revoked as of
June 15, 2005. This revocation was deemed appropriate, since the 8-hour standard is
more stringent, and therefore more protective of public health. However, the USEPA
did provide for anti-backsliding provisions to ensure continued progress toward
attainment of the 8-hour ozone NAAQS during the transition from the 1-hour ozone
Note: These
standard.
requirements
are different
Specifically, the following requirements that applied in an area for the 1-hour ozone
if you are an
NAAQS continue to apply for those areas with 8-hour ozone nonattainment and 1-hour 8-hr NAA &
1-hr AA, or
ozone nonattainment (Section 51.905(a)(1)):
Mandatory control measures - All areas designated nonattainment for the 8-hour ozone
NAAQS and designated nonattainment for the 1-hour ozone NAAQS at the time of
designation for the 8-hour NAAQS remain subject to control measures that applied by
virtue of the area's classification for the 1-hour standard.
3
69 Fed. Reg. 23951, (April 30, 2004).
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an 8-hr AA &
1-hr NAA.
Discretionary control measures - A State may revise or remove discretionary control
measures (including enforceable commitments) contained in its State Implementation
Plan (SIP) for the 1-hour ozone standard so long as the state demonstrates, consistent
with section 110(l), that such removal or modification will not interfere with attainment of
or progress toward the 8-hour ozone NAAQS (or any other applicable requirement of
the CAA).
With regard to planning SIPs, states would remain obligated to meet the CAA-mandated
Rate of Progress (ROP) emission reduction targets that applied for the 1-hour standard,
but discretionary measures adopted to meet those targets may be modified, if the State
makes the necessary showing under section 110(l).
Those areas designated nonattainment for the 1-hour NAAQS at the time of designation
for the 8-hour NAAQS, and subsequently designated nonattainment for the 8-hour
NAAQS, would not have the major source applicability cutoffs and offset ratios for the
area’s 1-hour classification continue to apply after revocation of the 1-hour NAAQS. In
addition, New Source Review (NSR) under the 1-hour ozone NAAQS was not retained.
Instead, NSR under the 8-hour ozone NAAQS now applies.
As of the effective date of revocation of the 1-hour ozone standard, the USEPA no
longer makes findings of failure to attain the 1-hour standard and, therefore:
(a) does not reclassify areas to a higher classification for the 1-hour standard based on
such a finding, and
(b) areas that are classified as severe or extreme for the 8-hour NAAQS will not be
obligated to impose fees as provided under sections 181(b)(4) and 185A of the CAA
under the 1-hour ozone standard.
In addition, these areas are no longer obligated to continue to demonstrate conformity
for the 1-hour ozone NAAQS as of the effective date of the revocation. Finally, states
had to continue to adhere to the emission budgets established by the NO x SIP Call after
the 1-hour standard was revoked. States retain the authority to revise control
obligations they have established for specific sources or source categories under the
NOx SIP Call rule so long as the state demonstrates, consistent with section 110(l), that
such modification will not interfere with attainment of or progress toward meeting the 8hour NAAQS or any other applicable requirement of the CAA.
2.3.1. Nonattainment Areas
2.4. Summary
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