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PollutionEngineering August 2012 : Page 23

The Facts of NAAQs A look at National Ambient Air Quality Standards and how they apply to electricity generating units. By JOSH FOSTER T h e Clean Air Act (CAA), which was last amended in 1990, w r equires the EPA to set National A mbient Air Quality Standards (NAAQS) for pollutants from many different sources considered harmful to public health and the environment. The CAA established two types of NAAQSs: • Primary standards set limits to protect public health, including the health of sensitive populations such as asthmatics, children and the elderly. • Secondary standards set limits to pro-tect public welfare, including protection against visibility impairment, damage to animals, crops, vegetation and buildings. The EPA established NAAQS for six pollutants that states and territories are primarily responsible for attaining. Those six pollutants, termed “criteria” pollut-ants, are: carbon monoxide, lead, nitrogen oxides, ozone, particulate matter and sul-fur oxides. See Figure 1 . States attain these standards, in part, by regulating emissions of these pollutants from certain stationary sources, such as electricity generating units. produce substantial amounts of harm-ful air emissions. According to the report Air Emissions and Electricity Generation at U.S. Power Plants , by the Government Accountability Office (GAO), “Fossil fuels are responsible for nearly all emissions of carbon dioxide, sulfur dioxide, and nitro-gen oxides from power plants.” The report states that “electricity gen-erating units at fossil fuel power plants Figure 1 Pollutant Carbon monoxide Lead Primary/ Secondary Primary Primary & Secondary Primary are among the largest emitters of sulfur dioxide and nitrogen oxides,” which have been linked to respiratory illnesses and acid rain, as well as “carbon dioxide, the primary greenhouse gas contributing to climate change.” Of the three fossil fuels, coal is the most widely used fuel in America, providing about 45 percent of electricity in 2010, fol-lowed by natural gas, which provided about Averaging Time 8 Hour 1 Hour Rolling 3 month avg 1 Hour Annual 8 Hour Annual 24 Hour 24 Hour Level 9 ppm 35 ppm 0.15 μg/m 3 100 ppb 53 ppb 0.075 ppm 15 μg/m 3 35 μg/m 3 150 μg/m 3 Form Not to be exceeded > once per year Not to be exceeded 98th percentile, avg over 3 years Annual Mean Annual 4th-highest daily maxi-mum 8-hr concentration, avg over 3 years Annual mean, avg over 3 years 98th percentile, avg over 3 years Not to be exceeded > once per year on avg over 3 years 99th percentile of 1-hour daily max concentrations, avg over 3 years Not to be exceeded > once per year Nitrogen dioxide Primary & Secondary Primary & Secondary Ozone Particle pollution PM2.5 Primary & Secondary Primary & Secondary Primary NAAQS and electricity The United States depends on a variety of fuels to generate electricity, including fossil fuels (coal, natural gas, and oil), nucle-ar power and renewable sources. Power plants that burn fossil fuels provide about 70 percent of U.S. electricity. But they also PM10 1 Hour 3 Hour 75 ppb 0.5 ppm Sulfur dioxide Secondary Units of measure for the standards are parts per million (ppm) by volume, parts per billion (ppb) by volume and micrograms per cubic meter of air (μg/m3). Data from EPA's NAAQS web page, located here: epa.gov/air/criteria.html AUGUST 2012 www.pollutionengineering.com 23

The Facts Of NAAQS

Josh Foster

A look at National Ambient Air Quality Standards and how they apply to electricity generating units.<br /> <br /> The Clean Air Act (CAA), which was last amended in 1990, equires the EPA to set National mbient Air Quality Standards (NAAQS) for pollutants from many different sources considered harmful to public health and the environment. The CAA established two types of NAAQSs:<br /> <br /> • Primary standards set limits to protect public health, including the health of sensitive populations such as asthmatics, children and the elderly.<br /> <br /> • Secondary standards set limits to protect public welfare, including protection against visibility impairment, damage to animals, crops, vegetation and buildings.<br /> The EPA established NAAQS for six pollutants that states and territories are primarily responsible for attaining. Those six pollutants, termed “criteria” pollutants, are: carbon monoxide, lead, nitrogen oxides, ozone, particulate matter and sulfur oxides. See Figure 1.<br /> <br /> States attain these standards, in part, by regulating emissions of these pollutants from certain stationary sources, such as electricity generating units.<br /> <br /> NAAQS and electricity<br /> <br /> The United States depends on a variety of fuels to generate electricity, including fossil fuels (coal, natural gas, and oil), nuclear power and renewable sources. Power plants that burn fossil fuels provide about 70 percent of U.S. electricity. But they also Produce substantial amounts of harmful air emissions. According to the report Air Emissions and Electricity Generation at U.S. Power Plants, by the Government Accountability Office (GAO), “Fossil fuels are responsible for nearly all emissions of carbon dioxide, sulfur dioxide, and nitrogen oxides from power plants.”<br /> <br /> The report states that “electricity generating units at fossil fuel power plants are among the largest emitters of sulfur dioxide and nitrogen oxides,” which have been linked to respiratory illnesses and acid rain, as well as “carbon dioxide, the primary greenhouse gas contributing to climate change.”<br /> <br /> Of the three fossil fuels, coal is the most widely used fuel in America, providing about 45 percent of electricity in 2010, followed by natural gas, which provided about 24 percent. Coal plays a critical role in the reliability of the electricity grid, especially in certain geographic areas, but coal-fired units also generally emit more air pollution than units burning natural gas or oil.<br /> <br /> According to the GAO, older coal-fired units without SO2 controls were responsible for the majority of SO2 emissions from fossil fuel units in 2010. Specifically, older coal-fired units without SO2 control equipment generated about 18 percent of electricity while producing 55 percent of SO2 emissions. As shown in Figure 2, older coal-fired units without SO2 controls accounted for 2.8 million tons of SO2 emissions, nearly three times as much as older units with SO2 controls. Among those coalfired units without SO2 controls, the majority (88 percent) were older units.<br /> <br /> Older units remain an important part of the electricity generating sector, particularly in certain regions of the United States. Older units in the Southeast, South Central and Great Lakes regions produced most of the electricity and emissions from Fossil fuel units (see Figure 3). According to the GAO, these air emissions not only affect local air quality, “they can also travel hundreds of miles to affect the air quality of downwind states.”<br /> <br /> Implementing NAAQS<br /> <br /> When the EPA establishes new NAAQS, or revises existing NAAQS, it sets in motion a series of actions aimed at ensuring that every state revises their rules to meet the updated standards.<br /> <br /> The CAA requires states to develop a general plan to attain and maintain the NAAQS and a specific plan to attain the standards. These plans, known as State Implementation Plans (SIPs), are developed by each state or local air quality management agency and must be submitted to the EPA for approval.<br /> <br /> The SIPs serve two main purposes:<br /> <br /> 1. Demonstrate that the state has the basic air quality management program components in place to implement a new or revised NAAQS.<br /> <br /> 2. Identify the emissions control requirements the state will rely upon to attain and/or maintain the primary and secondary NAAQS.<br /> <br /> Each state's SIP must contain specific elements as required by the CAA and are designed to prevent air quality deterioration while complying with NAAQS. As NAAQS change, states must submit SIP revisions to demonstrate their ability to attain the new or revised NAAQS.<br /> <br /> In addition to the basic required elements for managing air quality, the CAA requires states that are not meeting the NAAQS to adopt additional regulatory programs designed to achieve and maintain the relevant NAAQS.<br /> <br /> Congress recognized in the 1990 CAA amendments that the more densely populated Northeast states share the same airshed, as well as emissions sources and commuting patterns. In order to regionally address air quality in the Northeast, they created an area from Maine to Northern Virginia, calling it the Ozone Transport Region (OTR). States in the OTR are required to implement additional control measures that apply across the region. The 1990 CAA also required that the NAAQS be reviewed and updated at specific intervals, which also means that states must update their SIPs for approval as well.

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