Our Nation's Air 2018

Our Nation's Air 2018
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OUR NATION'S AIR
Welcome!
The U.S. Environmental Protection Agency (EPA) is committed to protecting public health by improving air quality and reducing air pollution. This annual report, entitled
Our Nation's Air
, summarizes the nation's air quality status and trends through 2017. Please read and enjoy the full report below and
download and share the one page summary.
Additional detail on air trends can be found at EPA's
AirTrends website.
Scroll down to read more or use the top menu to jump to a topic. If you encounter any issues viewing content, update or try opening the website in another browser.
The U.S. leads the world in having clean air and a strong economy due to implementation of the Clean Air Act and technological advancements from American innovators. Cleaner air provides important public health benefits.
Air Quality Improves as America Grows
Nationally, concentrations of air pollutants have dropped significantly since 1990:
Carbon Monoxide (CO) 8-Hour,
77%
Lead (Pb) 3-Month Average,
80%
Nitrogen Dioxide (NO
) Annual,
56%
Nitrogen Dioxide (NO
) 1-Hour,
50%
Ozone (O
) 8-Hour,
22%
Particulate Matter 10 microns (PM
10
) 24-Hour,
34%
Particulate Matter 2.5 microns (PM
2.5
) Annual,
41%
Particulate Matter 2.5 microns (PM
2.5
) 24-Hour,
40%
Sulfur Dioxide (SO
) 1-Hour,
88%
Numerous air toxics have declined with percentages varying by pollutant
During this same period, the U.S. economy continued to grow, Americans drove more miles and population and energy use increased.
Tip
Click pollutant names in the chart legend to hide or include trend lines, and hover over any line to display percentages above or below the most recent standard. Click the emission trends button below to open a popup window.
Line chart depicting overall decline in national air quality concentration averages for the criteria air pollutants from 1990 to 2017.
Source: U.S. EPA Air Quality System
Source: U.S. EPA National Emissions Inventory 2014 ver. 2
Emission Trends
Line chart depicting decline in national emissions from 1990 to 2017. The chart is a visual representation of the following text.
Emissions of key air pollutants continue to decline from 1990 levels:
Carbon Monoxide (CO),
65%
Ammonia (NH
),
22%
Nitrogen Oxides (NO
),
58%
Direct Particulate Matter 2.5 microns (PM
2.5
),
29%
Direct Particulate Matter 10 microns (PM
10
),
25%
Sulfur Dioxide (SO
),
88%
Volatile Organic Compounds (VOC),
40%
In addition, from 1990 to 2014 emissions of air toxics declined by 68 percent, largely driven by federal and state implementation of stationary and mobile source regulations, and technological advancements from American innovators.
*Wildfire data excluded for all pollutants except for NH
pre-2002; PM emissions also exclude miscellaneous emissions (i.e., agricultural dust and prescribed fire data). Visit the
emissions trends website
to learn more.
Air Pollution Includes Gases and Particles
Air pollution consists of gas and particle contaminants that are present in the atmosphere. Gaseous pollutants include sulfur dioxide (SO
), oxides of nitrogen (NO
), ozone (O
), carbon monoxide (CO), volatile organic compounds (VOCs), certain toxic air pollutants and some gaseous forms of metals. Particle pollution (PM
2.5
and PM
10
) includes a mixture of compounds that can be grouped into five major categories: sulfate, nitrate, elemental (black) carbon, organic carbon and crustal material.
Some pollutants are released directly into the atmosphere while other pollutants are formed in the air from chemical reactions. Ground-level ozone forms when emissions of NO
and VOCs react in the presence of sunlight. Air pollution impacts human health and the environment through a variety of pathways.
17 second animation showing air pollution pathways. Depicts cycle of sources, transport and transformation, deposition and effects.
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Six Common Pollutants
The Clean Air Act requires EPA to set national ambient air quality standards (NAAQS) for specific pollutants to safeguard human health and the environment. These standards define the levels of air quality that EPA determines are necessary to protect against the adverse impacts of air pollution based on scientific evidence. EPA has established standards for six common air pollutants, which are referred to as “criteria” pollutants.
Carbon monoxide (CO)
Lead (Pb)
Nitrogen dioxide (NO
Ozone (O
Particulate matter (PM), and
Sulfur dioxide (SO
Understanding Emission Sources Helps Control Air Pollution
Generally, emissions of air pollution come from
stationary fuel combustion sources (such as electric utilities and industrial boilers),
industrial and other processes (such as metal smelters, petroleum refineries, cement kilns and dry cleaners),
highway vehicles, and
non-road mobile sources (such as recreational and construction equipment, marine vessels, aircraft and locomotives).
As the chart shows, pollutants are emitted by a variety of sources. For example, electric utilities, part of the stationary fuel combustion category, release SO
, NO
and particles.
Bar chart depicting total national emissions and percentages by source category (stationary fuel combustion, industrial and other processes, highway vehicles and non-road mobile).
Source: U.S. EPA National Emissions Inventory 2014 ver. 2
Emission Inventories
EPA and states track direct emissions of air pollutants and emissions that contribute to the formation of key pollutants, also known as precursor emissions. Emissions data are compiled from many different organizations, including industry and state, tribal and local agencies. Some emissions data are based on actual measurements while others are estimates. For more information, please visit the
Air Emissions Inventories website.
Air Pollution Can Affect Our Health and Environment in Many Ways
Numerous scientific studies have linked air pollution to a variety of health problems.
People at greater risk for experiencing air pollution-related health effects may, depending on the pollutant, include older adults, children and those with heart and respiratory diseases —
30-second Healthy Heart video.
Ozone (O
Health Effects
Ozone exposure reduces lung function and causes respiratory symptoms, such as coughing and shortness of breath. Ozone exposure also aggravates asthma and lung diseases such as emphysema leading to increased medication use, hospital admissions, and emergency department visits. Exposure to ozone may also increase the risk of premature mortality from respiratory causes. Short-term exposure to ozone is also associated with increased total non-accidental mortality, which includes deaths from respiratory causes.
Environmental Effects
Ozone damages vegetation by injuring leaves, reducing photosynthesis, impairing reproduction and growth and decreasing crop yields. Ozone damage to plants may alter ecosystem structure, reduce biodiversity and decrease plant uptake of CO
. Ozone is also a greenhouse gas that contributes to the warming of the atmosphere.
Particulate Matter (PM)
Health Effects
Exposures to PM, particularly fine particles referred to as PM
2.5
, can cause harmful effects on the cardiovascular system including heart attacks and strokes. These effects can result in emergency department visits, hospitalizations and, in some cases, premature death. PM exposures are also linked to harmful respiratory effects, including asthma attacks.
Environmental Effects
Fine particles (PM
2.5
) are the main cause of reduced visibility (haze) in parts of the U.S., including many national parks and wilderness areas. PM can also be carried over long distances by wind and settle on soils or surface waters. The effects of settling include: making lakes and streams acidic; changing the nutrient balance in coastal waters and large river basins; depleting the nutrients in soil; damaging sensitive forests and farm crops; and affecting the diversity of ecosystems. PM can stain and damage stone and other materials, including culturally important objects such as statues and monuments.
Carbon Monoxide (CO)
Health Effects
Breathing elevated levels of CO reduces the amount of oxygen reaching the body’s organs and tissues. For those with heart disease, this can result in chest pain and other symptoms leading to hospital admissions and emergency department visits.
Environmental Effects
Emissions of CO contribute to the formation of CO
and ozone, greenhouse gases that warm the atmosphere.
Lead (Pb)
Health Effects
Depending on the level of exposure, lead may harm the developing nervous system of children, resulting in lower IQs, learning deficits and behavioral problems. Longer-term exposure to higher levels of lead may contribute to cardiovascular effects, such as high blood pressure and heart disease in adults.
Environmental Effects
Elevated amounts of lead accumulated in soils and fresh water bodies can result in decreased growth and reproductive rates in plants and animals.
Nitrogen Dioxide (NO
Health Effects
Short-term exposures to NO
can aggravate respiratory diseases, particularly asthma, leading to respiratory symptoms, hospital admissions and emergency department visits. Long-term exposures to NO
may contribute to asthma development and potentially increase susceptibility to respiratory infections.
Sulfur Dioxide (SO
Health Effects
Short-term exposures to SO
are linked with respiratory effects including difficulty breathing and increased asthma symptoms. These effects are particularly problematic for asthmatics while breathing deeply such as when exercising or playing. Short-term exposures to SO
have also been connected to increased emergency department visits and hospital admissions for respiratory illnesses, particularly for at-risk populations including children, older adults and those with asthma. SO
contributes to particle formation with associated health effects.
Oxides of Nitrogen and Sulfur (NO
and SO
Environmental Effects
Oxides of nitrogen react with volatile organic compounds to form ozone and react with ammonia and other compounds to form particle pollution resulting in associated public health and environmental effects. Deposition of nitrogen oxides contributes to the acidification and nutrient enrichment (eutrophication, nitrogen saturation) of soils and surface waters. These effects can change the diversity of ecosystems.
Deposition of sulfur oxides contributes to the acidification of soils and surface waters and mercury methylation in wetland areas. Sulfur oxides cause injury to vegetation and species loss in aquatic and terrestrial systems and contribute to particle formation with associated environmental effects. Sulfate particles contribute to the cooling of the atmosphere.
Hazardous Air Pollutants (also known as Air Toxics)
Health Effects
Air toxics may cause a broad range of health effects depending on the specific pollutant, the amount of exposure, and how people are exposed. People who inhale high levels of certain air toxics may experience eye, nose and throat irritation, and difficulty breathing. Long term exposure to certain air toxics can cause cancer and long-term damage to the immune, neurological, reproductive, and respiratory systems. Some air toxics contribute to ozone and particle pollution with associated health effects (see above).
Environmental Effects
Some toxic air pollutants accumulate in the food chain after depositing to soils and surface waters. Wildlife and livestock may also be harmed with sufficient exposure. Some toxic air pollutants contribute to ozone and particle pollution with associated environmental and climate effects (see above).
For more than forty years, the Clean Air Act has been a key part of cutting pollution as the U.S. economy has grown.
Economic Growth with Cleaner Air
Between 1970 and 2017, the combined emissions of the six common pollutants (PM
2.5
and PM
10
, SO
, NO
, VOCs, CO and Pb) dropped by 73 percent. This progress occurred while the U.S. economy continued to grow, Americans drove more miles and population and energy use increased.
To learn more about the EPA and environmental milestones to reduce pollution please visit the
EPA history website.
Click any of the legend items on the right side of the chart to hide or include trend lines. The y-axis may change based on the selections.
In 2008, the United States environmental technologies and services industry supported 1.7 million jobs. The industry generated approximately $300 billion in revenues and exported goods and services worth $44 billion - larger than exports of sectors such as plastics and rubber products. Environmental technology exports help the U.S. balance of trade, generating a $10.9 billion surplus in 2008.
Line chart depicting comparisons of growth areas such as gross domestic product, vehicle miles traveled, population, energy consumption, carbon dioxide emissions versus the decline in the aggregate emissions of the six common pollutants from 1970 to 2017.
Source: Various
Animated video background showing NASA satellite imagery of declining sulfur dioxide levels across the contiguous 48 states from 2005 to 2017.
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Today Americans breathe cleaner air and face lower risks of adverse health effects.
2005 - 2017 SO
satellite imagery courtesy of
NASA
Criteria Pollutant Trends Show Clean Air Progress
Based on NAAQS dropdown selection, a synchronized set of charts (air quality concentration chart, emissions stacked area chart and USA map of monitor locations) display. The first is a line chart depicting the overall decline in national air quality concentrations for criteria air pollutants from 1990 to 2017. The chart provides national concentration averages, 10th and 90th percentiles, and minimum and maximum values for each year.
Select a
NAAQS
to view concentration and emission trends
The blue band shows the distribution of air pollution levels among the national stat sites, displaying the middle 80 percent. Ninety percent of sites have concentrations below the top line, while ten percent have concentrations below the bottom line.
Source: U.S. EPA Air Quality System
Based on previous NAAQS dropdown selection: Stacked area chart depicting the corresponding national air emissions by the source categories of stationary fuel combusion, industrial and other processes, highway vehicles and non-road mobile from 1990 to 2017.
Source: U.S. EPA National Emissions Inventory 2014 ver. 2
Bar chart depicting national lead emissions and percentages by source category (stationary fuel combustion, industrial and other processes, highway vehicles and non-road mobile).
Source: U.S. EPA National Emissions Inventory 2014 ver. 2
Charts
Click emission tabs to change the emissions chart.
The play/pause button controls animation, or manually change the year by dragging the yellow circle in the chart or the slider's gray square.
Read about weather influences on ozone.
Few lead sites met
trend completeness criteria
to calculate national stats prior to 2010, and emissions data are only available for National Emissions Inventory (NEI) years.
Pressing the play button animates the synchronized charts and map cycling through 1990 to 2017 showing how both concentrations and emissions are changing, with a declining overall trend, during this period.
Year:
2000
Start animation
Pause animation
Based on previous NAAQS dropdown selection: USA map of corresponding monitor locations with information for each monitor such as Air Quality System (AQS) site ID, State, overall trend, annual concentration data and year.
Source: U.S. EPA Air Quality System
Map
Symbols indicate values above or below the most recent standard. Click any point to display annual concentration data. Double click the map to zoom in and click the home button to reset. Please be patient with map exports.
Understanding PM
2.5
Composition Helps Reduce Fine Particle Pollution
The different components that make up particle pollution come from specific sources and are often formed in the atmosphere. The major components, or species, are elemental carbon (EC), organic carbon (OC), sulfate and nitrate compounds, and crustal materials such as soil and ash.
As previously shown, PM
2.5
concentrations are declining. Assessing particle pollution concentrations along with composition data aids in understanding the effectiveness of pollution controls and in quantifying the impacts to public health, regional visibility, ecology and climate.
Click any point to display 2000-2016 annual and quarterly PM
2.5
speciation trends, and select maximize to enlarge the chart. Double click the map to zoom in and click the home button to reset.
USA map with PM2.5 speciation monitors depicted. Clicking a point opens a stacked bar graph depicting the 2000 to 2016 trends in PM2.5 speciation by component: sulfate, nitrate, elemental carbon, organic carbon, crustal material and sea-salt. Charts are available for each calendar year quarter, as well as an annual chart.
Source: U.S. EPA Air Quality System
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Source: U.S. EPA Air Quality System
Unhealthy Air Quality Days Trending Down
The Air Quality Index (AQI) is a color-coded index EPA uses to communicate daily air pollution for ozone, particle pollution, NO
, CO and SO
A value in the unhealthy range, above the national air quality standard for any pollutant, is of concern first for sensitive groups, then for everyone as the AQI value increases. Fewer unhealthy air quality days means better health, longevity, and quality of life for all of us.
Shown are the number of days in which the combined ozone and PM
2.5
AQI was unhealthy for sensitive groups (orange) or above (red, purple or maroon) for the years 2000-2017. Click the bar chart, or these links, to view the AQI retrospective reviews:
PM
2.5
and
ozone.
Variations in weather conditions play an important role in determining ozone concentrations. Ozone is more readily formed on warm, sunny days when the air is stagnant, and more limited when it is cloudy, cool, rainy, or windy.
Image of bar chart depicting the declining number of days reaching unhealthy for sensitive groups, or above, on the air quality index from 2000 to 2017. In 2000 the number of days was 2,076 and in 2017 729.
A look back: Combined Ozone and PM
2.5
in 2017
View
Air Quality Index (AQI) Forecast
Static image of the USA depicting today's air quality forecast.
EPA provides a daily AQI forecast so people can act to protect their health. Shown is the current AQI forecast for PM and ozone combined. This map and others can be found at the
AirNow website.
Air Quality in Nonattainment Areas Improves
EPA works collaboratively with state, local and tribal agencies to identify areas of the U.S. that do not meet the national ambient air quality standards (NAAQS). These areas, known as nonattainment areas, must develop plans to reduce air pollution and attain the NAAQS.
Through successful state led implementation, numerous areas across the country are showing improvement and fewer areas are in nonattainment. Since 2010, there were no violations of the standards for CO and NO
Shown is a snapshot of the 2008 ozone nonattainment area map. Click the map to view a larger interactive version that includes all current NAAQS nonattainment areas.
Image of map depicting the nonattainment areas for ozone. Click to open nonattainment areas story map in another browser window.
Nonattainment Areas
View
EPA has made significant progress in improving visibility in our nation's parks and wilderness areas.
Visibility Improves in Scenic Areas
EPA and other agencies, such as the National Park Service, monitor visibility trends in 155 of the 156 national parks and wilderness areas (i.e., Class I areas).
The map indicates several Class I areas have improving visibility or decreasing haze (indicated by the downward pointing arrows). To learn more about visibility in parks and view live webcams please visit this
National Park Service website
and
EPA's visibility story map.
Click any point to display 2000-2016 trends, and select maximize to enlarge the chart. Double click the map to zoom in and click the home button to reset.
The blue band shows the distribution of values among the national stat sites, displaying the middle 80 percent. Ninety percent of sites have values below the top line, while ten percent have values below the bottom line.
Source: IMPROVE
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Source: IMPROVE
Regional Haze Rule
The Regional Haze Rule, published in 1999, requires states to identify the most effective means of preserving conditions in Class I areas when visibility is at its best (based on the 20% best or cleanest visibility days monitored) and to gradually improve visibility when it is most impaired (based on the 20% worst visibility days monitored).
EPA works with state, local and tribal governments to reduce emissions of the 187 hazardous air pollutants.
Air Toxics Levels Trending Down
Ambient monitoring data show that some of the toxic air pollutants, such as benzene, 1,3-butadiene and several metals, are declining at most sites.
Points on the map indicate the long-term statistical trend direction: decreasing, increasing and no trend. Depicted in gray are sites where a trend direction is undetermined due to insufficient data.
Use the dropdown menu to select a pollutant, click any point to display trends, and select maximize to enlarge the chart. Double click the map to zoom in and click the home button to reset. View a
tabular summary
of air toxics trends.
The NATTS trends table, included as a supplementary visual to the USA map, depicts air toxics mean concentration trends at the 27 national air toxics trends stations from 2003 to 2016. A majority of stations show decreasing or no trend in air toxics across the country.
Based on the 2011 NATA, secondary pollution formation is the largest contributor to cancer risks nationwide, accounting for 47 percent of the risk. On-road mobile sources contribute the most risk from directly emitted pollutants (about 18 percent).
Select an air toxic to view concentration trends
USA map depicting air toxics mean concentration trends from 2003 to 2016 at the 27 national air toxics trends stations and numerous other monitors tracking air toxics. A vast majority of stations show decreasing or no trend in air toxics across the country.
The blue band shows the distribution of air pollution levels among the national stat sites, displaying the middle 80 percent. Ninety percent of sites have concentrations below the top line, while ten percent have concentrations below the bottom line.
Source: Phase XII of the Ambient Monitoring Archive (AMA)
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Source: Phase XI of the Ambient Monitoring Archive (AMA)
National Air Toxics Assessment (NATA)
EPA frequently relies on modeling studies to supplement air toxic monitoring data. One such modeling study, the National Air Toxics Assessment (NATA), is a nationwide study of ambient levels, inhalation exposures, and health risks associated with toxic air pollutant emissions. While NATA cannot be used to directly define trends, it does put ambient levels in context to appropriate health endpoints. To learn more please visit the
NATA website.
The National Emissions Inventory (NEI) is a detailed estimate of air emissions that include criteria pollutants and hazardous air pollutants.
National Emissions Inventory
The National Emissions Inventory (NEI) is a comprehensive and detailed air emissions estimate of criteria pollutants, criteria precursors and hazardous air pollutants from air emissions sources. The NEI is released every three years with version 2 of the 2014 NEI being released in early 2018. The NEI is based upon data provided by state, local, and tribal air agencies for sources in their jurisdictions and supplemented by data developed by the EPA.
EPA published an online interactive report summarizing aspects of the NEI while also providing a tool for users to explore emissions data. Click on the image to explore the NEI report, or for more information please visit the
National Emissions Inventory website.
Image of National Emissions Inventory 2014 report dashboard. Click map image to open NEI story map in another browser window.
National Emissions Inventory Report
View
Our Nation's Air Continues to Improve
However, work must continue to ensure healthy air for all communities. EPA and our partners at the state, tribal and local levels will continue to work to address the complex air quality problems we face.
Download and share the one page summary
and scroll down for additional resources.
Approximately 111 million Americans lived in counties with air quality concentrations above the level of one or more NAAQS in 2017.
The downloadable EPA air trends infographic has four graphics depicting improving air quality trends since 1970. The top left chart shows the 262 percent increase of the United States gross domestic product against a 73 percent drop in air pollutant emissions since 1970. The top right chart shows decreasing national average ozone and particulate matter concentrations since 1990 with the averages falling below the most recent standard. The bottom right chart shows the 65 percent reduction in unhealthy air quality days from 2000. And the bottom left chart shows the descreasing emissions from 1990 for sulfur dioxide, nitrous oxides, volatile organic compounds, direct particulate matter and carbon monoxide.
Social Media
Use the share button
at the top to share this report with others, and follow the latest EPA activities to protect human health and the environment using the links below.
Source code, data and documentation are available for download at the GitHub repository below.
GitHub
Additional Resources
Please visit other EPA air quality related websites.
AirTrends
AirNow
AirCompare
AirData
Air Emissions
to ask a question, provide feedback, or report a problem.