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 (O3) 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 (NOX). 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
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
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 (www.airnow.gov) 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
http://www.dep.state.fl.us/air/air_quality/airquality.htm.
The national ambient air quality standard for ground-level ozone is 0.075 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 2009-2011. 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 0.075 ppm (or 75 ppb), the ozone standard is violated at the monitor
for the three-year period of measurement.
3
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
Florida 4th Highest 8-hour Ozone Values
All Monitors
120
100
ppb
80
60
Average
MAX
40
MIN
20
0
2000
2002
2004
2006
2008
2010
Year
Figure 3: Showing the trend in the 4th 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 NOX. Research has found that in Florida and
throughout the southeastern U.S. NOX 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 NOX throughout the state and region have been steadily declining.
The three largest source categories of NOX 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 NOX emissions. Figure 4
shows the downward trends in emissions of NOX from these sources since 2000.2
2
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
Florida NOX Emissions from Motor Vehicles, Industrial
Facilities, and Nonroad Engines
800,000
700,000
Tons per Year
600,000
500,000
Motor
Vehicles
400,000
Industrial
Facilities
300,000
Nonroad
Engines
200,000
100,000
0
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
Year
Figure 4: Showing the trends in statewide NOX emissions from on-road motor
vehicles, industrial facilities, and nonroad engines from 2000 through 2010.
As seen in Figure 4, NOX 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 NOX emissions from industrial facilities in Florida has also taken
place since 2000. This trend is largely due to emission reductions in the power sector.
Emissions of NOX 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
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 “PM10,” 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 “PM2.5,” 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 PM2.5 in the atmosphere
may be visible as smoke or haze. Figure 5 illustrates the comparative size of PM10 and PM2.5
particles.
Figure 5: Illustrating the size of PM10 and PM2.5 particles in microns (µm = micron).
7
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 PM2.5 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 (SO2), volatile organic compounds (VOC), and nitrogen oxides (NOX). 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
Data on the chemical composition of PM2.5 (“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 (http://vista.cira.colostate.edu/improve/Publications/Reports/2011/2011.htm), the
IMPROVE program presents data showing that in Florida and throughout the southeastern
U.S., the two principal components of PM2.5 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 PM2.5 concentrations. Sulfate aerosols
are formed in the atmosphere by chemical reactions involving gaseous emissions of SO2.
Particulate organic matter accounts for approximately 30-40 percent of annual PM2.5
concentrations across the state. The organic particulate portion of PM2.5 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 (PM2.5) 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 PM2.5 levels are not common in Florida, but episodes of high concentrations have
occurred as result of wildfires. The EPA Air Quality Index (AQI) website (www.airnow.gov)
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 PM2.5 levels, the website
advises that “people with heart or lung disease, older adults, and children should reduce
prolonged or heavy exertion.” For PM2.5, 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 PM10
year-round at 24 locations in 14 counties and PM2.5 at 24 locations in 17 counties across the
state. Various reports and real-time tools are available for viewing the data at
http://www.dep.state.fl.us/air/air_quality/airquality.htm.
The U.S. Environmental Protection Agency (EPA) has established air quality standards for
both PM10 and PM2.5 to protect public health. The national ambient air quality standard for
PM10 is 150 micrograms per cubic meter (µg/m3), 24-hour average, not to be exceeded
more than once per year, on average, over three years. A violation of the PM10 standard
occurs at a monitor when the number of days with concentrations above 150 µg/m3 (the
“expected exceedance rate”) is greater than 1.0 per year, averaged over three years.
The air quality standard for PM2.5 has two parts: 12 micrograms per cubic meter, annual
mean, averaged over three years; and 35 micrograms per cubic meter, 98th percentile 24-
9
hour average, averaged over three years.3 For each part of the PM2.5 standard, annual and
24-hour, the three-year average is termed the “compliance value,” or “design value.” If a
county has more than one PM2.5 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 PM10 or PM2.5 standards.
For the three-year period 2009-2011, every PM10 monitor in the state has an expected
exceedance rate of 0.0 days per year. Figure 7 displays the annual and 24-hour PM2.5
compliance values for each county with complete data for the three-year period 2009-2011.
It shows that no areas in Florida violate the annual or 24-hour PM2.5 air quality standards.
Figure 7 also shows that the highest PM2.5 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 PM2.5 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 98th percentile of the daily values is
determined, and that value is averaged with the 98th 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 PM2.5 standard is violated at the monitor for the three-year period of measurement.
10
Figure 7: Showing statewide compliance with the national air quality standards for
PM2.5. A “green” value of 36 micrograms per cubic meter or greater would represent
a violation of the current 24-hour PM2.5 standard; a “dark blue” value of 12.1
micrograms per cubic meter or greater would represent a violation of the annual
PM2.5 standard.
11
Figure 8: Comparing Florida’s annual PM2.5 levels with those of neighboring states.
12
While Florida complies with the national air quality standards for both PM10 and PM2.5, the
statewide trends in PM2.5 levels and precursor emissions are of particular interest because of
the greater potential of PM2.5 to affect human health. These trends are examined below.
What has been the Trend in PM2.5 Levels in Florida?
Figures 9 and 10 display the trend in the annual and 98th percentile 24-hour PM2.5 levels,
respectively, across the state since 2000. For both averaging periods, the trend has been
downward with some year-to-year variability, especially for the 24-hour value. The
improvement in PM2.5 air quality over this period has been the result of ongoing emission
reductions from industrial facilities, on-road motor vehicles, and nonroad engines.
Florida Annual PM2.5 Values
All Monitors
16
14
12
µg/m3
10
8
Average
Max
6
Min
4
2
0
2000
2002
2004
2006
2008
2010
Year
Figure 9 Showing the trend in the annual PM2.5 values over the statewide monitoring
network from 2000 through 2011 (µg/m3 = micrograms per cubic meter).
13
Florida 98th Percentile 24-hour PM2.5 Values
All Monitors
35
30
µg/m3
25
20
Average
15
Max
Min
10
5
0
2000
2002
2004
2006
2008
2010
Year
Figure 10: Showing the trend in the 98th percentile 24-hour PM2.5 values over the
statewide monitoring network from 2000 through 2011 (µg/m3 = micrograms per
cubic meter).
What has been the Trend in PM2.5-Producing Emissions in Florida?
As stated above, part of the PM2.5 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 SO2, VOC, and NOX. Of these
precursor pollutants, SO2 is of particular importance because the resulting sulfate aerosol
accounts for roughly 40 percent of the measured PM2.5 concentrations across the state.
As shown in Figure 11, emissions of SO2 from industrial facilities in Florida have been
steadily declining since 2000. This trend is largely due to emission reductions in the power
sector. Emissions of SO2 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 SO2
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 SO2 emissions decrease,
both in Florida and in neighboring states, PM 2.5 concentrations are also expected to
decrease.
14
Florida SO2 Emissions from Industrial Facilities
700,000
Tons per Year
600,000
500,000
400,000
300,000
200,000
100,000
0
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
Year
Figure 11: Showing the trend in statewide sulfur dioxide (SO2) emissions from
industrial facilities from 2000 through 2010.
The organic particulate portion of the PM2.5 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 (http://www.metro4-sesarm.org):
Florida Acres
Burned (2007)
PM2.5 Emissions
(tons per year)
Wildfire
376,078
45,913
Agriculture Lands
Prescribed Fire
746,687
20,696
1,128,929
46,632
Type of Fire
Forest Lands
Prescribed Fire
According to this study, the estimated PM2.5 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
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 (http://www.floridaforestservice.com/index.html). 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.
Florida Acres Burned Prescribed Fire and Wildfire
3,000,000
Acres
2,500,000
2,000,000
Wildfire - All
Causes
1,500,000
Agricultural Lands
Prescribed Fire
1,000,000
Forest Lands
Prescribed Fire
500,000
0
2000
2002
2004
2006
2008
2010
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 PM2.5 concentrations. Figure 13 shows the
downward trends in statewide PM10 emissions from these sources from 2000 through 2010.
The PM10 trends are shown because data are not available to accurately determine the PM2.5
trends from all three source categories. However, for these particular source categories,
PM10 emissions provide a reasonably close estimate of the PM2.5 emissions. As with the
downward trends in NOX emissions from these source categories, these downward trends
are expected to continue for the next several years.
16
Florida PM10 Emissions from Industrial
Facilities, Motor Vehicles, and Nonroad Engines
50,000
45,000
40,000
Industrial
Facilities
Tons per Year
35,000
30,000
Motor
Vehicles
25,000
20,000
Nonroad
Engines
15,000
10,000
5,000
0
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
Year
Figure 13: Showing the trends in statewide PM10 emissions from industrial facilities,
on-road motor vehicles, and nonroad engines from 2000 through 2010.
17