Section 1.0 Background and Overview of Federal Requirements
Due to the severity of the health and welfare effects associated with ground-level ozone, the Clean Air Act (CAA) required the United States Environmental Protection Agency (EPA) to establish National Ambient Air Quality Standards (NAAQS) designed to protect public health and the environment. The CAA allows the EPA 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, and damage to animals, crops, vegetation, and buildings. Until 1997, the ozone NAAQS was established at 0.12 parts per million (ppm) over a 1-hour period for both the primary and secondary standards. On July 18, 1997, EPA promulgated an ozone standard of 0.08 ppm, measured over an 8-hour period, i.e., the 8-hour standard (62 FR 38856).
1.2 Ozone Formation
Ozone is produced in complex chemical reactions when its precursors, volatile organic compounds (VOCs) and oxides of nitrogen (NOx), 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 and damage vegetation resulting in reduced crop yield.
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, or 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 (SO2) and lead, which are emitted directly and can be controlled at their source, reducing ozone concentrations poses additional control challenges.
1.2.1 Ozone Precursor - Oxides of Nitrogen (NOx)
Oxides of nitrogen are a group of gases including nitric oxide (NO) and nitrogen dioxide (NO2). NO2 is a reddish-brown, highly reactive gas that is formed in the air through the oxidation of NO. When NO2 reacts with other chemicals in the atmosphere, it not only results in the formation of ozone, but it also forms particulate matter (PM), haze and acid rain. Sources of NO and NO2 include motor vehicle exhaust (including both gasoline-fueled vehicles and diesel-fueled vehicles), the burning of coal, oil or natural gas, and industrial processes such as welding, electroplating and dynamite blasting. Figure 1 shows the national breakdown of NOx emissions by category. In this chart, fuel combustion refers to stationary sources (i.e., power plants). Transportation is considered a mainly localized contributor of NOX, while stationary source fuel combustion has transport impacts, making it more of a regional issue.
Although most NOx is emitted as NO, it is readily converted to NO2 in the atmosphere. In the home, gas stoves and heaters produce substantial amounts of nitrogen dioxide. As 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.
1.2.2 Ozone Precursor - Volatile Organic Compounds (VOCs)
VOCs 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 with a short atmospheric lifespan, while others can have a very long lifespan. The short-lived compounds contribute substantially to atmospheric photochemical reactions and thus the formation of ozone.
VOCs are used in the manufacture of, or are present in, many products used daily in both homes and businesses. Some products, like gasoline, actually are VOCs. VOCs are used as fuels (gasoline and heating oil) and are components of many common household items like polishes, paints, cosmetics, perfumes and cleansers. They are also used in industry as degreasers and solvents, and in dry cleaning. VOCs are present in many fabrics and furnishings, construction materials, adhesives and paints. In offices, VOCs can be found in correction fluid, magic markers, paper, rubber bands, invisible tape and other products. The names of many VOCs may be familiar: carbon tetrachloride, trichloroethene (TCE), tetrachloroethene (PCE), trichloroethane (TCA), 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. Human-made VOCs are primarily emitted into the air by motor vehicle exhaust, industrial processes and from the evaporation of solvents, oil-based paints and gasoline from gas pumps.
Figure 2 shows the national breakdown of VOC emissions by category. As with the NOx chart, fuel combustion refers to stationary sources (i.e., power plants).
1.3 Health and Welfare Effects
Ground-level ozone can irritate lung airways and cause skin 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 pre-existing 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. 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. In fact, on July 11, 2007, EPA proposed to lower the ozone standard even more because of documented health effects of ozone (72 FR 37818).
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 injury to 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, rubber products and paints.
1.4 Clean Air Act Amendments of 1990
During the fall of 1990, and after years of debate, the United States Congress approved changes to the federal CAA. These amendments were the first changes to the CAA since 1977. In addition to adding provisions that addressed concerns associated with acid rain, hazardous air pollutants and stratospheric ozone concerns, Congress significantly changed the way in which states were to address remaining attainment problems for criteria pollutants which include ground level ozone.
As opposed to the past when areas were designated as attainment, non-attainment or unclassifiable, the 1990 Amendments required areas to also be classified according to severity. For those areas with more severe classifications, additional requirements were included in the CAA and additional time was also provided for those areas to demonstrate attainment with the NAAQS for ozone.
NAAQS were developed to protect the public health from the impacts associated with various forms of air pollution. In 1979, EPA promulgated the 0.12 ppm 1-hour ozone standard (40 FR 8202, February 8, 1979).
1.5 8-hour Ozone NAAQS
On July 18, 1997, EPA promulgated an ozone standard of 0.08 ppm, measured over an 8-hour period, i.e., the 8-hour standard (62 FR 38856). In general, the 8-hour standard is more protective of public health and more stringent than the 1-hour standard. The CAA and the Transportation Equity Act for the 21 Century (TEA-21) required EPA to designate all areas by July 2000. The NAAQS rule was challenged and in May 1999, the U.S. Court of Appeals for the D.C. Circuit issued a decision remanding, but not vacating, the 8-hour ozone standard. The court noted that EPA is required to designate areas for any new or revised NAAQS in accordance with the CAA and addressed a number of other issues, which are not related to designations. American Trucking Assoc. v. EPA, 175 F.3d 1027, 1047-48, on rehearing 195 F.3d 4 (D.C. Cir. 1999). EPA sought review of the two aspects of that decision in the U.S. Supreme Court. In February 2001, the Supreme Court upheld EPA's authority to set the NAAQS and remanded the case back to the D.C. Circuit for disposition of issues the Court did not address in its initial decision. Whitman v. American Trucking Assoc., 121 S.Ct. 903, 911-914, 916-919 (2001) (Whitman). In March 2002, the D.C. Circuit rejected all remaining challenges to the 8-hour ozone standard. American Trucking Assoc. v. EPA, 283 F.3d 355 (D.C. Cir. 2002) ATA III). The process for designations following promulgation of a NAAQS is contained in §107(d)(1) of the CAA. For the 8-hour NAAQS, TEA-21 extended by one year the time for EPA to designate areas for the 8-hour NAAQS. Thus, EPA was required to designate areas for the 8-hour NAAQS by July 2000. However, HR3645 (EPA's appropriation bill in 2000) restricted EPA's authority to spend money to designate areas until June 2001 or the date of the Supreme Court ruling on the standard, whichever came first. In 2003, several environmental groups filed suit in district court claiming EPA had not met its statutory obligation to designate areas for the 8-hour NAAQS. EPA entered into a consent decree, which required EPA to issue the designations by April 15, 2004.
Under the requirements of the CAA, states have a responsibility to ensure that all areas within their jurisdiction meet and maintain air quality levels that do not exceed the NAAQS prescribed by the federal government.
1.6 Designation and Requirements
On April 30, 2004, EPA designated the Poughkeepsie, NY area, comprised of the New York State counties of Dutchess, Orange and Putnam as non-attainment (moderate classification) for the federal 8-hour ozone NAAQS, effective June 15, 2004 (69 FR 23858). Consequently, New York State must develop a State Implementation Plan (SIP) to demonstrate how it will come into compliance with the ozone standard.