FLORIDA S OZONE AND PARTICULATE MATTER AIR QUALITY TRENDS

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1 FLORIDA S OZONE AND PARTICULATE MATTER AIR QUALITY TRENDS Florida Department of Environmental Protection Division of Air Resource Management December 2012 Various pollutants are found in the air throughout the country. Many of these pollutants occur in low concentrations and do not pose a threat to public health. Others are a problem only in local areas near strong sources of emissions. However, some air pollutants can occur in high concentrations spread over wide areas, thereby potentially affecting the health of many people. The pollutants of most concern in this latter category are ground-level ozone and particulate matter, especially particulate matter in the form of fine particles. Florida s residents and visitors can take comfort in the knowledge that the state s air is among the cleanest in the nation with respect to ground-level ozone and particulate matter. All areas of the state comply with the national ambient air quality standards for these pollutants established by the U.S. Environmental Protection Agency (EPA) to protect public health. Market forces and air pollution control programs currently in place have led to lower ozone and particulate matter levels throughout the state in recent years. In addition, the Department of Environmental Protection (DEP) expects further emission reductions and improvements in Florida s air quality to occur over the next several years. GROUND-LEVEL OZONE Ground-level ozone has long been the air pollutant of greatest concern to Florida. Throughout the 1980s, the state s largest urban counties were designated by EPA as nonattainment for ozone meaning that ozone levels violated the national ambient air quality standard for ozone in effect during those years. By the early 1990s conditions had improved, and all Florida counties were meeting the standard. Since then EPA has twice strengthened the national air quality standard for ozone to better protect public health. At the same time ozone levels across the state have been trending downward, and the state has remained in attainment with the air quality standards. What is Ozone? Ozone (O 3 ) is the principal component of urban smog. Ozone is not emitted directly into the air from pollutant sources; rather, it is formed in the lower atmosphere through a series of chemical reactions involving emissions of so-called precursor pollutants. The precursor pollutants that lead to ozone formation are volatile organic compounds (VOC) and nitrogen oxides (NO X ). Volatile organic compounds are produced by both biogenic sources (VOC released from vegetation through natural processes) and anthropogenic sources (VOC emitted by human activities). Anthropogenic sources of VOC include fuel combustion in engines and industrial operations; some types of chemical manufacturing operations; evaporation of certain solvents in consumer and commercial products; and evaporation of volatile fuels such as gasoline. Nitrogen oxides are emitted from on-road motor vehicles; nonroad engines such as locomotives and construction equipment; fuel-burning power plants and industrial facilities; and other combustion sources. 1

2 Strong sunlight drives the atmospheric chemical reactions that lead to ozone formation. Thus, ozone concentrations build up during the day and subside at night. The process of ozone formation is illustrated in Figure 1. Figure 1: Illustrating the formation of ground-level ozone. It should be noted that ozone occurs naturally in the stratosphere, about 10 to 30 miles above the earth's surface, where it forms a layer that protects life on earth from the sun's harmful ultraviolet radiation. Ozone poses a threat to public health, however, when elevated concentrations occur near the ground in the air people breathe. Ground-level ozone formed as a result of man-made emissions can reach unhealthy levels when the weather is hot and dry. Light winds can contribute to a further build-up of ozone on such days. High ozone levels may cause inflammation and irritation of the respiratory tract, particularly during physical activity. The resulting symptoms can include breathing difficulty, coughing, and throat irritation. Breathing ozone can also worsen asthma attacks and increase the susceptibility of the lungs to infections, allergens, and other air pollutants. Groups that are 2

3 sensitive to ozone include children and adults who are active outdoors, and people with respiratory disease such as asthma. High ozone levels occur on only a few days per year, typically from April through October when weather conditions are most conducive to ozone formation. The EPA Air Quality Index (AQI) website ( allows the public to check on current and predicted air quality levels in their communities. If the color-coded AQI reaches orange based on elevated ozone levels, EPA advises that active children and adults, and people with respiratory disease should limit prolonged outdoor exertion. For ozone, the number of orange days averages less than four per year for all Florida cities. How is Ozone Measured and Reported? The Department of Environmental Protection (DEP) and ten county agencies monitor ozone year-round at 57 locations in 33 counties across the state. Various reports and real-time tools are available for viewing the data on the DEP website at The national ambient air quality standard for ground-level ozone is parts per million (ppm) or, equivalently, 75 parts per billion (ppb). Compliance with the standard is based on the three-year average of the annual fourth-highest maximum daily eight-hour ozone concentration. 1 This statistic is termed the ozone compliance value, or design value. If a county has more than one ozone monitoring site, the compliance value for the county is based on the monitor with the highest individual compliance value. How do Ozone Levels in Florida Compare to the Ozone Standard? Figure 2 displays ozone compliance values for each county with complete data for the threeyear period It shows that no areas in Florida violate the 75 ppb air quality standard. While all areas of the state comply with the air quality standard, the map also shows that the highest ozone levels occur along the northern Gulf Coast. This portion of the state experiences more days with light winds than other parts of the state and is more influenced by emissions from nearby states. Statewide, the highest ozone levels of the year most often occur from spring through early summer, and again in early autumn. In midsummer, increased cloudiness, afternoon showers, and stronger subtropical winds can interfere with the build-up of ozone on days when such conditions prevail. 1 Ozone levels are measured continuously at each monitoring location. From the continuous readings, the highest 8-hour average concentration is determined for each day. The days of the year are then ranked according to each day s highest 8-hour value. The fourth-highest day of the year is determined, and that value is averaged with the fourth-highest days of the previous two years to determine a compliance value (or design value ) for the threeyear period. If the compliance value exceeds ppm (or 75 ppb), the ozone standard is violated at the monitor for the three-year period of measurement. 3

4 Figure 2: Showing statewide compliance with the national ambient air quality standard for ground-level ozone. A value of 76 parts per billion (ppb) or greater would represent a violation of the standard. What has been the Trend in Ozone Levels in Florida? Ozone levels in Florida have declined significantly since the 1980s when seven Florida counties were designated nonattainment. Since 2000, the trend in ozone levels across the state has been gradually downward as shown in Figure 3. The improvement in ozone air quality over the years has been the result of ongoing emission reductions from industries and motor vehicles. 4

5 ppb 120 Florida 4 th Highest 8-hour Ozone Values All Monitors Average MAX MIN Year Figure 3: Showing the trend in the 4 th highest 8-hour daily ozone values over the statewide monitoring network from 2000 through 2011 (ppb = parts per billion). What has been the Trend in Ozone-Producing Emissions in Florida? As stated above, ground-level ozone is formed through a series of atmospheric chemical reactions involving emissions of VOC and NO X. Research has found that in Florida and throughout the southeastern U.S. NO X emissions play a more important role than anthropogenic VOC emissions in the formation of ground-level ozone. Over the last decade or so, emissions of NO X throughout the state and region have been steadily declining. The three largest source categories of NO X emissions in Florida are on-road motor vehicles (cars, trucks, buses), industrial facilities (power plants, industrial boilers, cement kilns, waste-to-energy facilities, and other industrial processes), and nonroad engines (outdoor power equipment, recreational vehicles, farm and construction machinery, lawn and garden equipment, marine vessels, locomotives, aircraft and many other applications). These source categories account for over 90 percent of Florida s total NO X emissions. Figure 4 shows the downward trends in emissions of NO X from these sources since Motor vehicle emissions are from the EPA MOVES-2010 emissions model applied to Florida vehicle-miles-traveled (VMT) data from the Florida Department of Transportation. Industrial facilities emissions are from Annual Operating Report data in the DEP Air Resource Management System (ARMS). Nonroad emissions are from the EPA NONROAD emissions model, version 2008a, run in default mode for Florida. 5

6 Tons per Year Florida NO X Emissions from Motor Vehicles, Industrial Facilities, and Nonroad Engines 800, , , , , , , ,000 Motor Vehicles Industrial Facilities Nonroad Engines Year Figure 4: Showing the trends in statewide NO X emissions from on-road motor vehicles, industrial facilities, and nonroad engines from 2000 through As seen in Figure 4, NO X emissions from on-road motor vehicles has declined since 2000, despite an approximate 20 percent increase in the number of vehicle miles traveled (VMT) in the state over the same period. The decrease is due to the fact that newer cars and trucks individually emit less pollution than older ones more than compensating for the increase in VMT. This trend is expected to continue as newer, even cleaner vehicles continue to replace older models on the road. A significant reduction in NO X emissions from industrial facilities in Florida has also taken place since This trend is largely due to emission reductions in the power sector. Emissions of NO X from Florida s power plants have decreased by about 80 percent since 2000 (and by nearly 85 percent since the late 1990s). This trend is expected to continue as a number of older, higher-emitting electrical generating units are scheduled to be replaced with cleaner, natural gas burning units in the next few years. 6

7 PARTICULATE MATTER Particulate matter is a general term for the complex mixture of very small particles found in the air. Particulate matter is of concern as an air pollutant because it is wide spread and has the potential to impact the health of many people. What is Particulate Matter? Particulate matter is made up of a number of components, including sulfate and nitrate aerosols, organic particles, and soil or dust particles. Some particles are emitted directly into the air; others are formed in the atmosphere through chemical and physical processes. The size of the particles is linked to their potential for causing health problems. Particles less than or equal to 10 micrometers (microns) in diameter, referred to as PM 10, can pass through the nose and throat and enter the lungs. Ten microns is about one-seventh the diameter of human hair. Particles less than or equal to 2.5 microns in diameter, referred to as "fine particles or PM 2.5, are especially important in terms of potential health effects. Individual fine particles are about one-thirtieth of the diameter of human hair and can be seen only with an electron microscope, but high concentrations of PM 2.5 in the atmosphere may be visible as smoke or haze. Figure 5 illustrates the comparative size of PM 10 and PM 2.5 particles. Figure 5: Illustrating the size of PM 10 and PM 2.5 particles in microns (µm = micron). 7

8 Particles lifted into the air by the wind or vehicular traffic, and those emitted by dusty operations such as crushing and grinding, are typically larger than 2.5 microns but smaller than 10 microns in diameter. These coarse particles are primarily associated with the aggravation of underlying respiratory conditions such as asthma. Fine particles, those less than 2.5 microns in diameter, can be emitted directly into the air by on-road motor vehicles, nonroad engines, forest fires, agricultural burning, and industrial combustion processes. In addition, a large portion of the PM 2.5 found in the atmosphere is not the result of direct emissions; instead, it is formed by chemical and physical processes in the atmosphere involving emissions of gaseous precursor pollutants such as sulfur dioxide (SO 2 ), volatile organic compounds (VOC), and nitrogen oxides (NO X ). These direct and indirect processes are illustrated in Figure 6. Figure 6: Illustrating the direct and indirect sources of particulate matter in the air. 8

9 Data on the chemical composition of PM 2.5 ( speciation data ) as measured by a number of monitoring sites across the country, including several in Florida, are collected and compiled by the federal government through the Interagency Monitoring of Protected Visual Environments (IMPROVE) program and the EPA Chemical Speciation Network. In its latest report ( the IMPROVE program presents data showing that in Florida and throughout the southeastern U.S., the two principal components of PM 2.5 in the atmosphere are sulfate aerosols and particulate organic matter. Throughout Florida, sulfate aerosols (measured as ammonium sulfate) account for roughly 40 percent of the annual PM 2.5 concentrations. Sulfate aerosols are formed in the atmosphere by chemical reactions involving gaseous emissions of SO 2. Particulate organic matter accounts for approximately percent of annual PM 2.5 concentrations across the state. The organic particulate portion of PM 2.5 is made up of particles emitted directly by fossil fuel combustion sources and biomass burning, as well as aerosols formed in the atmosphere by chemical reactions involving both man-made and natural sources of VOC. Fine particles (PM 2.5 ) can penetrate deeply into the lungs and enter the bloodstream. They are associated with such health effects as increased hospital admissions and emergency room visits for heart and lung disease, increased respiratory symptoms and disease, decreased lung function, and even premature death. Sensitive groups that appear to be at greatest risk to such effects include those with underlying heart or lung disease, older adults, and children. In addition to effects on health, elevated levels of PM 2.5 are the major cause of reduced visibility, or haze, in many parts of the U.S. High PM 2.5 levels are not common in Florida, but episodes of high concentrations have occurred as result of wildfires. The EPA Air Quality Index (AQI) website ( allows the public to check on current and predicted air quality levels in their communities. If the color-coded AQI index reaches orange based on elevated PM 2.5 levels, the website advises that people with heart or lung disease, older adults, and children should reduce prolonged or heavy exertion. For PM 2.5, the number of orange days averages less than one per year for all areas of Florida. How is Particulate Matter Measured and Reported? The Department of Environmental Protection (DEP) and eight county agencies monitor PM 10 year-round at 24 locations in 14 counties and PM 2.5 at 24 locations in 17 counties across the state. Various reports and real-time tools are available for viewing the data at The U.S. Environmental Protection Agency (EPA) has established air quality standards for both PM 10 and PM 2.5 to protect public health. The national ambient air quality standard for PM 10 is 150 micrograms per cubic meter (µg/m 3 ), 24-hour average, not to be exceeded more than once per year, on average, over three years. A violation of the PM 10 standard occurs at a monitor when the number of days with concentrations above 150 µg/m 3 (the expected exceedance rate ) is greater than 1.0 per year, averaged over three years. The air quality standard for PM 2.5 has two parts: 12 micrograms per cubic meter, annual mean, averaged over three years; and 35 micrograms per cubic meter, 98 th percentile 24-9

10 hour average, averaged over three years. 3 For each part of the PM 2.5 standard, annual and 24-hour, the three-year average is termed the compliance value, or design value. If a county has more than one PM 2.5 monitoring site, the compliance value for the county is based on the monitor with the highest individual compliance value. How do Particulate Matter Levels in Florida Compare to the National Air Quality Standards? No areas in Florida have ever been in nonattainment for either the PM 10 or PM 2.5 standards. For the three-year period , every PM 10 monitor in the state has an expected exceedance rate of 0.0 days per year. Figure 7 displays the annual and 24-hour PM 2.5 compliance values for each county with complete data for the three-year period It shows that no areas in Florida violate the annual or 24-hour PM 2.5 air quality standards. Figure 7 also shows that the highest PM 2.5 levels though still in compliance with air quality standards are found in northern Florida. This portion of the state experiences more days with light winds than other parts of the state and is more influenced by pollutant emissions from nearby states. Figure 8 illustrates this point by showing that higher PM 2.5 levels are found as one continues northward into Georgia and Alabama, states with even more stagnant days and more upwind pollution. 3 The average PM2.5 concentration level for each calendar day of monitor operations is determined. The days of the year are then ranked according to each day s concentration value. The 98 th percentile of the daily values is determined, and that value is averaged with the 98 th percentile daily values of the previous two years to determine a compliance value (or design value ) for the three-year period. If the compliance value exceeds 35 micrograms per cubic meter, the 24-hour PM 2.5 standard is violated at the monitor for the three-year period of measurement. 10

11 Figure 7: Showing statewide compliance with the national air quality standards for PM 2.5. A green value of 36 micrograms per cubic meter or greater would represent a violation of the current 24-hour PM 2.5 standard; a dark blue value of 12.1 micrograms per cubic meter or greater would represent a violation of the annual PM 2.5 standard. 11

12 Figure 8: Comparing Florida s annual PM 2.5 levels with those of neighboring states. 12

13 While Florida complies with the national air quality standards for both PM 10 and PM 2.5, the statewide trends in PM 2.5 levels and precursor emissions are of particular interest because of the greater potential of PM 2.5 to affect human health. These trends are examined below. What has been the Trend in PM 2.5 Levels in Florida? Figures 9 and 10 display the trend in the annual and 98 th percentile 24-hour PM 2.5 levels, respectively, across the state since For both averaging periods, the trend has been downward with some year-to-year variability, especially for the 24-hour value. The improvement in PM 2.5 air quality over this period has been the result of ongoing emission reductions from industrial facilities, on-road motor vehicles, and nonroad engines. 16 Florida Annual PM 2.5 Values All Monitors µg/m Average Max Min Year Figure 9 Showing the trend in the annual PM 2.5 values over the statewide monitoring network from 2000 through 2011 (µg/m 3 = micrograms per cubic meter). 13

14 35 Florida 98 th Percentile 24-hour PM 2.5 Values All Monitors µg/m Average Max Min Year Figure 10: Showing the trend in the 98th percentile 24-hour PM 2.5 values over the statewide monitoring network from 2000 through 2011 (µg/m 3 = micrograms per cubic meter). What has been the Trend in PM 2.5 -Producing Emissions in Florida? As stated above, part of the PM 2.5 found in the atmosphere is emitted directly from various combustion sources, and part is formed in the atmosphere by chemical and physical processes involving gaseous precursor pollutants such as SO 2, VOC, and NO X. Of these precursor pollutants, SO 2 is of particular importance because the resulting sulfate aerosol accounts for roughly 40 percent of the measured PM 2.5 concentrations across the state. As shown in Figure 11, emissions of SO 2 from industrial facilities in Florida have been steadily declining since This trend is largely due to emission reductions in the power sector. Emissions of SO 2 from Florida s power plants have decreased by about 75 percent since 2000 (and by nearly 85 percent since the late 1990 s). The downward trend in SO 2 emissions is expected to continue as older oil-fired and coal-fired generating units are replaced with new natural gas burning units across the state. As SO 2 emissions decrease, both in Florida and in neighboring states, PM 2.5 concentrations are also expected to decrease. 14

15 Tons per Year 700,000 Florida SO 2 Emissions from Industrial Facilities 600, , , , , , Year Figure 11: Showing the trend in statewide sulfur dioxide (SO 2 ) emissions from industrial facilities from 2000 through The organic particulate portion of the PM 2.5 concentrations measured across the state is made up of particles of various origins. The relative importance of the numerous sources that contribute to organic particulate matter in the air is difficult to determine. However, one of the more significant sources of organic particles in the southeastern U.S. is fire on agricultural and forest lands, both prescribed fire and wildfire. Emissions from these activities are not available for every year, but the following estimates have been made for the year 2007 as part of a recent air quality study conducted by the Southeastern States Air Resource Managers organization ( Florida Acres PM 2.5 Emissions Type of Fire Burned (2007) (tons per year) Wildfire 376,078 45,913 Agriculture Lands Prescribed Fire 746,687 20,696 Forest Lands Prescribed Fire 1,128,929 46,632 According to this study, the estimated PM 2.5 emissions for 2007 from wildfire and prescribed fire on forest lands are nearly the same, but the number of acres affected by wildfire is only 15

16 Acres one-third the number of forest acres on which prescribed burning was conducted. Thus, to the extent prescribed fire prevents the occurrence of more highly polluting wildfire, it provides an air quality benefit. Furthermore, the smoke from prescribed fire can be controlled so as to reduce risks to public health and safety. The Florida Forest Service (FFS) is a national leader in the responsible use of prescribed fire for promotion of forest health and prevention of wildfires. Figure 12 shows the number of acres burned by prescribed fire and wildfire from 2000 through 2011 according to data compiled by the FFS ( An increase in the number of forest acres treated by prescribed fire over this time period can be seen, but the trend in overall fire-related emissions cannot be inferred from this data due to variability in the extent and intensity of wildfires over the years. 3,000,000 Florida Acres Burned - Prescribed Fire and Wildfire 2,500,000 2,000,000 1,500,000 Wildfire - All Causes Agricultural Lands Prescribed Fire 1,000,000 Forest Lands Prescribed Fire 500, Year Figure 12: Comparing the number of acres burned by prescribed fire and wildfire. Emissions from industrial facilities, on-road motor vehicles and nonroad equipment also contribute to the organic particulate fraction of PM 2.5 concentrations. Figure 13 shows the downward trends in statewide PM 10 emissions from these sources from 2000 through The PM 10 trends are shown because data are not available to accurately determine the PM 2.5 trends from all three source categories. However, for these particular source categories, PM 10 emissions provide a reasonably close estimate of the PM 2.5 emissions. As with the downward trends in NO X emissions from these source categories, these downward trends are expected to continue for the next several years. 16

17 Tons per Year 50,000 45,000 40,000 35,000 30,000 25,000 20,000 15,000 10,000 5,000 Florida PM 10 Emissions from Industrial Facilities, Motor Vehicles, and Nonroad Engines Industrial Facilities Motor Vehicles Nonroad Engines Year Figure 13: Showing the trends in statewide PM 10 emissions from industrial facilities, on-road motor vehicles, and nonroad engines from 2000 through