The Plain English Guide

to the Clean Air Act

United States Office of Air Quality Planning and Standards Publication No. EPA-456/K-07-001 

Environmental Protection Research Triangle Park, NC April 2007 

Agency 
Contents

Why Should You Be Concerned About Air Pollution? .........................................................................1

Air Pollution and Your Health 

Air Pollution and the Environment 

Air Pollution and the Economy 

Understanding the Clean Air Act.........................................................................................................2

Key Elements of the Clean Air Act ......................................................................................................4

 Cleaning Up Commonly Found Air Pollutants......................................................................................... 4

 Cars, Trucks, Buses, and Nonroad Equipment ......................................................................................... 8

 Interstate and International Air Pollution ............................................................................................... 10

 Clearing the Air in Our National Parks .................................................................................................. 12

 Reducing Acid Rain .............................................................................................................................. 14

 Reducing Toxic Air Pollutants ................................................................................................................ 16

 Protecting the Stratospheric Ozone Layer .............................................................................................. 17

 Permits and Enforcement ....................................................................................................................... 19

 Public Participation ............................................................................................................................... 20

How the Clean Air Act Is Working ....................................................................................................21

Ways to Reduce Air Pollution ............................................................................................................22

Contact Information ..........................................................................................................................23
Air pollution 

And in 

cause death. 

Other pollutants make their way up into the upper 

and cataracts (eye damage). 

and the chemicals that form acid 

Those 

pollutants can also harm fish and 

other aquatic life. 

ou could go days without food and 

must have air to live. 

lakes, and animals. In addition to damaging the 

buildings, monuments, and statues. It not only 

The Clean Air Act has helped change the way many 

of us work or do business. In some cases, it has 

and policies in the Clean Air Act. 

United States have been diagnosed 

Air pollution can trigger and aggravate 

of Public Health, Minneapolis, MN 

Y

be severely affected by air pollution. 

can also aggravate health problems for the elderly 

and others with heart or respiratory diseases. 

Some toxic chemicals released in the air such as 

benzene or vinyl chloride are highly toxic and can 

cause cancer, birth defects, long term injury to the 

lungs, as well as brain and nerve damage. 

some cases, breathing these chemicals can even 

atmosphere, causing a thinning of the protective 

ozone layer. This has led to changes in the 

environment and dramatic increases in skin cancers 

Air Pollution and the Environment 

Air pollution isn’t just a threat to our health, it also 

damages our environment. Toxic air pollutants 

rain and ground-level ozone can 

damage trees, crops, wildlife, lakes 

and other bodies of water. 

Why Should You Be 

Concerned About Air Pollution? 

hours without water, but you would 

last only a few minutes without air. 

On average, each of us breathes over 

3,000 gallons of air each day. You 

However, did you know that 

breathing polluted air can make you sick? 

Air pollution can damage trees, crops, other plants, 

natural environment, air pollution also damages 

reduces how far you can see in national parks and 

cities, it even interferes with aviation. 

In 1970, Congress created the Environmental 

Protection Agency (EPA) and passed the Clean Air 

Act, giving the federal government authority to 

clean up air pollution in this country. Since then, 

EPA and states, tribes, local governments, industry, 

and environmental groups have worked to establish 

a variety of programs to reduce air pollution levels 

across America. 

even changed the way we live. This guide provides 

a brief introduction to the programs, philosophies, 

Air Pollution and Your Health 

Breathing polluted air can make your eyes and nose 

burn. It can irritate your throat and make breathing 

difficult. In fact, pollutants like 

tiny airborne particles and groundlevel ozone can trigger respiratory 

problems, especially for people 

with asthma. Today, nearly 30 

million adults and children in the 

with asthma. Asthma sufferers can 

Testing for asthma in Minneapolis, Minnesota. 

asthma in children. 

Ian Greaves, M.D., University of Minnesota School 

1

Why should you be concerned about air pollution? 
Understanding the Clean Air Act 

Air Pollution and the Economy 

The health, environmental, and economic impacts of air 

pollution are significant. Each day, air pollution causes 

thousands of illnesses leading to lost days at work and 

school. Air pollution also reduces agricultural crop and 

commercial forest yields by billions of dollars each year. 

United States. 

Since 1970, 

• the six commonly found air pollutants 

• 

• 

cleaner and will be even cleaner in the 

• 

chemicals has ceased. 

At the same time, 

• 

• 

• 

By reducing air pollution, the Clean Air 

Act has led to significant improvements in 

human health and the environment in the 

have decreased by more than 50 

percent, 

air toxics from large industrial sources, 

such as chemical plants, petroleum 

refineries, and paper mills have been 

reduced by nearly 70 percent, 

new cars are more than 90 percent 

future, and 

production of most ozone-depleting 

the U.S. gross domestic product, or 

GDP, has tripled, 

energy consumption has increased by 

50 percent, and 

vehicle use has increased by almost 

200 percent. 

Understanding 

the Clean Air Act 

n October 1948, a thick cloud of air 

pollution formed above the industrial 

town of Donora, Pennsylvania. The 

killed 20 people and caused sickness 

"Killer Fog." The smog was so thick that buses could 

not run without guides walking ahead of them 

Events like these alerted us to the dangers that air 

pollution poses to public health. Several federal and 

Act of 1963, which established funding for the study 

in 1970. 

Since 

pollutant emissions. The 1990 Amendments also 

Clean Air Act Roles and 

Responsibilities 

They also 

I

Brief History of the Clean Air Act 

cloud which lingered for five days, 

in 6,000 of the town’s 14,000 people. In 1952, over 

3,000 people died in what became known as London’s 

carrying lanterns. 

state laws were passed, including the original Clean Air 

and the cleanup of air pollution. But there was no 

comprehensive federal response to address air pollution 

until Congress passed a much stronger Clean Air Act 

That same year Congress created the EPA and 

gave it the primary role in carrying out the law. 

1970, EPA has been responsible for a variety of Clean 

Air Act programs to reduce air pollution nationwide. 

In 1990, Congress dramatically revised and expanded 

the Clean Air Act, providing EPA even broader authority 

to implement and enforce regulations reducing air 

placed an increased emphasis on more cost-effective 

approaches to reduce air pollution. 

The Clean Air Act is a federal law covering the entire 

country. However, states, tribes and local governments 

do a lot of the work to meet the Act’s requirements. 

For example, representatives from these agencies work 

with companies to reduce air pollution. 

review and approve permit applications for industries 

or chemical processes. 

2 
EPA’s Role 

Under the Clean Air Act, EPA sets limits on certain air 

pollutants, including setting limits on how much can 

be in the air anywhere in the United States. This helps 

to ensure basic health and environmental protection 

from air pollution for all Americans. The Clean Air Act 

also gives EPA the authority to limit emissions of air 

pollutants coming from sources like chemical plants, 

utilities, and steel mills. Individual states or tribes may 

have stronger air pollution laws, but they may not have 

weaker pollution limits than those set by EPA. 

EPA must approve state, tribal, and local agency plans 

for reducing air pollution. If a plan does not meet the 

necessary requirements, EPA can issue sanctions against 

the state and, if necessary, take over enforcing the Clean 

Air Act in that area. 

EPA assists state, tribal, and local agencies by providing 

research, expert studies, engineering designs, and 

funding to support clean air progress. Since 1970, 

Congress and the EPA have provided several billion 

dollars to the states, local agencies, and tribal nations to 

accomplish this. 

State and Local Governments’ Role 

It makes sense for state and local air pollution 

agencies to take the lead in carrying out the Clean Air 

Act. They are able to develop solutions for pollution 

problems that require special understanding of local 

industries, geography, housing, and travel patterns, as 

well as other factors. 

State, local, and tribal governments also monitor air 

quality, inspect facilities under their jurisdictions and 

enforce Clean Air Act regulations. 

States have to develop State Implementation Plans 

(SIPs) that outline how each state will control air 

pollution under the Clean Air Act. A SIP is a 

collection of the regulations, programs and policies 

that a state will use to clean up polluted areas. The 

states must involve the public and industries through 

hearings and opportunities to comment on the 

development of each state plan. 

3

The Clean Air Act includes a variety of approaches for dealing with 

pollution released by large industrial sources. 

Tribal Nations’ Role 

In its 1990 revision of the Clean Air Act, Congress 

recognized that Indian Tribes have the authority to 

implement air pollution control programs. 

EPA’s Tribal Authority Rule gives Tribes the ability 

to develop air quality management programs, write 

rules to reduce air pollution and implement and 

enforce their rules in Indian Country. While state and 

local agencies are responsible for all Clean Air Act 

requirements, Tribes may develop and implement only 

those parts of the Clean Air Act that are appropriate for 

their lands. 

Understanding the Clean Air Act 
Key Elements 

of the Clean Air Act 

focus on: 

■

pollutants that cause smog, haze, acid rain, and other 

■

■

chemical plants, gas stations, and powerplants) and 

4 

Key Elements of the Clean Air Act

How Smog Is Formed 

including cars, manufacturing 

and chemical plants, and 

pollutants. Winds blow the 

summer sun causes chemical 

level ozone—a principal 

component of smog. 

Hours after the smog-forming 

E

Cleaning Up Commonly Found Air 

Pollutants 

Six common air pollutants (also known as "criteria 

Of the six pollutants, particle 

Details about these two 

For information about 

based guidelines) for setting permissible levels. The 

PA’s mission is to protect human health 

and the environment. To achieve this 

mission, EPA implements a variety of 

programs under the Clean Air Act that 

 reducing outdoor, or ambient, concentrations of air 

problems; 

 reducing emissions of toxic air pollutants that are 

known to, or are suspected of, causing cancer or 

other serious health effects; and 

 phasing out production and use of chemicals that 

destroy stratospheric ozone. 

These pollutants come from stationary sources (like 

mobile sources (like cars, trucks, and planes). 

Many pollution sources, 

products used in homes, 

release smog-forming 

pollutants away from their 

sources and the heat of the 

reactions that form groundpollutants are released from 

their sources, smog pollutes 

the air, often many miles away 

from where the pollutants 

were released. 

pollutants") are found all over the United States. They 

are particle pollution (often referred to as particulate 

matter), ground-level ozone, carbon monoxide, sulfur 

oxides, nitrogen oxides, and lead. These pollutants 

can harm your health and the environment, and 

cause property damage. 

pollution and ground-level ozone are the most 

widespread health threats. 

pollutants are discussed below. 

the other common pollutants, visit EPA’s website at 

www.epa.gov/air/urbanair/. 

EPA calls these pollutants "criteria" air pollutants 

because it regulates them by developing human healthbased and/or environmentally-based criteria (scienceset of limits based on human health is called primary 

standards. Another set of limits intended to prevent 

environmental and property damage is called secondary 

standards. A geographic area with air quality that 

is cleaner than the primary standard is called an 

"attainment" area; areas that do not meet the primary 

standard are called "nonattainment" areas. 
EPA has been developing programs to cut emissions 

of these commonly found air pollutants since the 

Clean Air Act was passed in 1970. It's a big job, and 

although a great deal of progress has been made, it 

will take time to make the air healthy throughout 

the country. For the latest information on air quality 

trends in the U.S., visit www.epa.gov/airtrends. There 

are still several areas of the country, including many 

large cities, that are classified as nonattainment for 

at least one of the six common pollutants. Despite 

continued improvements in air quality, millions of 

people live in areas with monitoring data measuring 

unhealthy levels of pollution. 

To see whether your area is attainment or 

nonattainment, contact your local air pollution 

control agency or visit EPA’s website at: www.epa. 

gov/air/urbanair. 

Particle Pollution 

Particle pollution, also known as particulate matter 

(PM), includes the very fine dust, soot, smoke, and 

droplets that are formed from chemical reactions, 

and produced when fuels such as coal, wood, or 

oil are burned. For example, sulfur dioxide and 

nitrogen oxide gases from motor vehicles, electric 

power generation, and industrial facilities react with 

sunlight and water vapor to form particles. Particles 

may also come from fireplaces, wood stoves, 

unpaved roads, crushing and grinding operations, 

and may be blown into the air by the wind. 

EPA scientists and other health experts are concerned 

about particle pollution because very small or "fine" 

particles can get deep into the lungs. These fine 

particles, by themselves, or in combination with other 

air pollutants, can cause increased emergency room 

visits and hospital admissions for respiratory illnesses, 

and tens of thousands of deaths each year. They can 

aggravate asthma, cause acute respiratory symptoms 

such as coughing, reduce lung function resulting in 

shortness of breath, and cause chronic bronchitis. 

The elderly, children, and asthmatics are particularly 

susceptible to health problems caused by breathing 

fine particles. Individuals with pre-existing heart or 

lung disease are also at an increased risk of health 

problems due to particle pollution. 

Particles also cause haze reducing visibility in places 

like national parks and wilderness areas that are 

5

Particle Pollution 

ways. 

■

■

diesel. 

■

■

Protecting the Public from 

EPA is tackling particle pollution in several different 

EPA's health-based standards include limits for 

smaller-sized or "fine" particles. States are taking 

actions to meet these standards. To learn more, visit 

www.epa.gov/particles. 

EPA's rule for Clean Diesel Trucks and Buses will 

result in a fleet of heavy-duty trucks and buses 

that will be 95 percent cleaner than today's trucks 

and buses. To learn more, visit www.epa.gov/otaq/ 

Visibility protection regulations are designed to 

reduce emissions that cause haze in our national 

parks and wilderness areas. States are working 

together on strategies to improve visibility in these 

natural areas. To learn more, visit www.epa.gov/ 

visibility. 

EPA created the Air Quality Index (AQI) to provide 

simple information on local air quality, the health 

concerns for different levels of air pollution, 

and how people can protect their health when 

pollutants reach unhealthy levels. To learn more, 

visit www.airnow.gov. 

known for their scenic vistas. These are places where 

we expect to see clearly for long distances. In many 

parts of the United States, pollution has reduced the 

distance and clarity of what we see by 70 percent. 

Fine particles can remain suspended in the air and 

travel long distances with the wind. For example, over 

20 percent of the particles that form haze in the Rocky 

Mountains National Park have been estimated to come 

from hundreds of miles away. 

Particles also make buildings, statues and other outdoor 

structures dirty. Trinity Church in downtown New York 

City was black until a few years ago, when cleaning off 

almost 200 years worth of soot brought the church’s 

stone walls back to their original light pink color. 

Before the 1990 Clean Air Act went into effect, 

EPA set limits on airborne particles smaller than 10 

micrometers in diameter called PM10. These are tiny 

particles (seven of these particles lined up next to each 

other would cover a distance no wider than a human 

hair). Research has shown that even smaller particles 

(1/4 the size of a PM10 particle) are more likely to 

harm our health. So in 1997, EPA published limits for 

fine particles, called PM2.5. To reduce particle levels, 

additional controls are being required on a variety of 

sources including power plants and diesel trucks. 

Particle Pollution 
Ground-level Ozone

They 

active healthy adults, such as construction workers, 

coughing) when exposed to low levels of ozone 

during periods of moderate exertion. 

x). VOCs 

industrial facilities. The solvents used in paints and 

x

The 

Hair sprays, interior and exterior paints, foam plastic 

use, or disposal can contribute to air pollution. 

But I Thought the Ozone 

to some forms of UV light has been linked to 

damage. 

causing lung inflammation. 

So, whether ozone is "good" or "bad" depends 

Ground-level Ozone 

Ground-level ozone is a primary component of 

smog. Ground-level ozone can cause human health 

problems and damage forests and agricultural 

crops. Repeated exposure to ozone can make people 

more susceptible to respiratory infections and lung 

inflammation. It also can aggravate pre-existing 

respiratory diseases, such as asthma. Children 

are at risk from ozone pollution because they are 

outside, playing and exercising, during the summer 

days when ozone levels are at their highest. 

also can be more susceptible because their lungs 

are still developing. People with asthma and even 

can experience a reduction in lung function and an 

increase in respiratory symptoms (chest pain and 

The two types of chemicals that are the main ingredients 

in forming ground-level ozone are called volatile organic 

compounds (VOCs) and nitrogen oxides (NO

are released by cars burning gasoline, petroleum 

refineries, chemical manufacturing plants, and other 

other consumer and business products contain VOCs. 

The 1990 Clean Air Act has resulted in changes in 

product formulas to reduce the VOC content of those 

products. Nitrogen oxides (NO ) are produced when 

cars and other sources like power plants and industrial 

boilers burn fuels such as gasoline, coal, or oil. 

reddish-brown color you sometimes see when it is 

smoggy comes from the nitrogen oxides. 

products (such as disposable foam cups), charcoal fire 

starter — all are consumer products whose production, 

Volatile organic compounds (VOC) emitted from the use 

of consumer products can cause or contribute to ozone 

levels that violate the air quality standards EPA set for 

ground-level ozone. 

In 1998, EPA issued a rule limiting VOC emissions from 

consumer products. It requires many United States 

manufacturers, importers, and distributors to limit the VOC 

content of their products. EPA also issued a rule limiting 

emissions from architectural coatings (exterior and interior 

house paints, wood and roof coatings). 

Pollution Prevention in Consumer Products 

Layer Was a Good Thing?! 

It is! In the upper atmosphere, called the 

stratosphere, ozone naturally occurs and forms 

a protective layer that shields the Earth from 

some of the sun’s ultraviolet (UV) light. Exposure 

cataracts (eye damage), skin cancer, and plant 

This high-altitude ozone, therefore, 

protects human health and the environment. 

Ground-level ozone, on the other hand, is harmful. 

It can cause serious health problems and damage 

forests and crops. Ground-level ozone affects 

the respiratory system, aggravating asthma and 

on its location – at ground level, it is "bad," in the 

upper atmosphere, it is "good." 

6
The pollutants that react to form ground-level ozone 

literally cook in the sky during the hot summertime 

season. It takes time for smog to form—several hours 

from the time pollutants get into the air until the 

ground-level ozone reaches unhealthy levels. For more 

information on days when air quality is expected to be 

unhealthy, visit EPA’s website at www.airnow.gov. 

Weather and the lay of the land (for example, hills 

around a valley, high mountains between a big 

industrial city and suburban or rural areas) help 

determine where ground-level ozone goes and how bad 

it gets. When temperature inversions occur (warm air 

stays trapped near the ground by a layer of cooler air) 

and winds are calm, high concentrations of groundlevel ozone may persist for days at a time. As traffic 

and other sources add more ozone-forming pollutants 

to the air, the ground-level ozone gets worse. 

How the Clean Air Act Reduces Air 

Pollution Such as Particle Pollution and 

Ground-level Ozone 

First, EPA works with state governors and tribal 

government leaders to identify "nonattainment" areas 

where the air does not meet allowable limits for a 

common air pollutant. States and tribes usually do 

much of the planning for cleaning up common air 

pollutants. They develop plans, called State/Tribal 

Implementation Plans, to reduce air pollutants to 

allowable levels. Then they use a permit system as 

part of their plan to make sure power plants, factories, 

and other pollution sources meet their goals to clean 

up the air. 

The Clean Air Act requirements are comprehensive 

and cover many different pollution sources and a 

variety of clean-up methods to reduce common air 

pollutants. Many of the clean-up requirements for 

particle pollution and ground-level ozone involve large 

industrial sources (power plants, chemical producers, 

and petroleum refineries), as well as motor vehicles 

(cars, trucks, and buses). Also, in nonattainment areas, 

controls are generally required for smaller pollution 

sources, such as gasoline stations and paint shops. 

tons) of the total amount of fine particle 

pollution (PM2.5

If you use wood:

wood. 

Wood Stoves and Fireplaces 

Residential wood smoke (from wood stoves, 

fireplaces, and outdoor wood-fired hydronic 

heaters) contributes 6 percent (420,000 

) directly emitted in the 

United States each year. That contribution 

can be significantly higher in some areas 

with increased wood burning. EPA and state 

and local agencies are working on a number 

of fronts to help reduce residential wood 

smoke pollution. To learn more, visit 

www.epa.gov/woodstoves. 

 - replace your old wood stove or fireplace 

with an EPA-certified model, and get 

more heat and less pollution while 

burning less wood;

 - burn only clean, dry, "seasoned" wood;

 - regularly remove ashes from your wood 

stove and store outside away from 

Ground-level Ozone and Particle Pollution 

7 
Cars, Trucks, Buses and, “Nonroad” Equipment

Cars, Trucks, Buses, and 

“Nonroad” Equipment 

Today, motor vehicles are responsible for nearly onehalf of smog-forming volatile organic compounds 

(VOCs), more than half of the nitrogen oxide (NOx) 

emissions, and about half of the toxic air pollutant 

emissions in the United States. Motor vehicles, 

including nonroad vehicles, now account for 75 percent 

of carbon monoxide emissions nationwide. 

The total vehicle miles people travel in the United 

States increased 178 percent between 1970 and 2005 

and continues to increase at a rate of two to three 

percent each year. In the United States, there are 

more than 210 million cars and light-duty trucks on 

the road. In addition, the types of cars people drive 

have changed greatly since 1970. Beginning in the 

late 1980s, Americans began driving more vans, sport 

utility vehicles (SUVs), and pickup trucks as personal 

vehicles. By the year 2000, these “light-duty trucks” 

accounted for about half of the new passenger car 

sales. These bigger vehicles typically consume more 

gasoline per mile and many of them pollute three to 

five times more than cars. 

The Clean Air Act takes a comprehensive approach 

to reducing pollution from these sources by requiring 

manufacturers to build cleaner engines; refiners to 

produce cleaner fuels; and certain areas with air 

pollution problems to adopt and run passenger vehicle 

inspection and maintenance programs. EPA has issued 

a series of regulations affecting passenger cars, diesel 

trucks and buses, and so-called “nonroad” equipment 

(recreational vehicles, lawn and garden equipment, etc.) 

that will dramatically reduce emissions as people buy 

new vehicles and equipment. 

Cleaner Cars 

The Clean Air Act required EPA to issue a series 

of rules to reduce pollution from vehicle exhaust, 

refueling emissions and evaporating gasoline. As a 

result, emissions from a new car purchased today 

are well over 90 percent cleaner than a new vehicle 

purchased in 1970. This applies to SUVs and pickup 

trucks, as well. Beginning in 2004, all new passenger 

vehicles – including SUVs, minivans, vans and pick-up 

trucks – must meet more stringent tailpipe emission 

standards. This marks the first time that light-duty 

trucks, including SUVs, pickups, and minivans are 

subject to the same national pollution standards as 

cars. As more of these cleaner vehicles enter the 

national fleet, harmful emissions will drop dramatically. 

These reductions would not be possible without 

cleaner, very low sulfur gasoline and diesel fuel. In 

addition to their direct emissions benefits, cleaner 

fuels enable sophisticated emission control devices to 

effectively control pollution. Congress recognized the 

importance of cleaner fuels to reducing motor vehicle 

emissions and gave EPA authority to regulate fuels in 

the Clean Air Act. 

Lead and Other Toxic Pollutants 

One of EPA’s earliest accomplishments was the 

elimination of lead from gasoline. Elevated levels of 

lead can damage organs and the brain and nervous 

system, and affect the heart and blood. Adverse health 

effects range from behavior disorders and anemia to 

mental retardation and permanent nerve damage. 

Children are especially susceptible to lead’s toxic effects 

on the nervous system, which can result in learning 

deficits and lowered IQ. In the mid-1970s, EPA 

began its lead phase-out effort by proposing to limit 

the amount of lead that could be used in gasoline. By 

the summer of 1974, unleaded gasoline was widely 

8
available around the country, improving public health 

and providing protection for the catalytic converters 

that manufacturers began to install on all new 

vehicles. This effort was followed by even stronger 

restrictions on the use of lead in gasoline in the 1980s. 

In 1996, leaded gasoline was finally banned as a result 

of the Clean Air Act. 

Under the Clean Air Act, EPA has also put into place 

standards to reduce toxic air emissions from mobile 

sources. These standards will cut toxic emissions from 

gasoline, vehicles, and even gas containers. 

Reformulated Gasoline 

The Clean Air Act requires certain metropolitan 

areas with the worst ground-level ozone pollution 

to use gasoline that has been reformulated to reduce 

air pollution. Other areas, including the District of 

Columbia and 17 states, with ground-level ozone 

levels exceeding the public health standards, have 

voluntarily chosen to use reformulated gasoline. 

Reformulated gasoline reduces emissions of toxic air 

pollutants, such as benzene, as well as pollutants that 

contribute to smog. 

Low Sulfur Fuels 

Beginning in 2006, refiners have been supplying 

gasoline with sulfur levels much lower than in the 

past, reducing the sulfur levels in gasoline by 90 

percent. Sulfur in gasoline inhibits a vehicle’s catalytic 

converter from effectively cleaning up the exhaust. 

The advanced vehicle emission control systems 

in passenger cars and light trucks are even more 

sensitive to sulfur, so reducing the sulfur content of 

gasoline will ensure that vehicle emission control 

devices are effective in reducing pollution. In addition 

to cutting emissions from new vehicles, lower sulfur 

fuel will result in lower emissions from vehicles 

currently on the road. 

Since 2006, refiners have begun supplying diesel 

fuel with very low sulfur levels for highway diesel 

vehicles. As with gasoline vehicles, efficient new 

emission controls on diesel engines require this “UltraLow Sulfur Diesel” (ULSD) fuel to function properly. 

Highway diesel fuel sulfur levels are 97 percent cleaner 

than diesel prior to 2006. In 2007, refiners began 

reducing sulfur in diesel fuel used for nonroad diesel 

engines, such as construction equipment. 

Cars, Trucks, Buses and, “Nonroad” Equipment 

The Clean Air Act requires the installation of vapor recovery nozzles 

at gas stations in certain areas. These gas pump nozzles reduce the 

release of gasoline vapor into the air when people put gas in their cars. 

Alternative Fuels 

The Clean Air Act encourages development and sale 

of alternative fuels. Alternative fuels are transportation 

fuels other than gasoline and diesel, including natural 

gas, propane, methanol, ethanol, electricity, and 

biodiesel. These fuels can be cleaner than gasoline 

or diesel and can reduce emissions of harmful 

pollutants. Renewable alternative fuels are made from 

biomass materials like wood, waste paper, grasses, 

vegetable oils, and corn. They are biodegradable and 

reduce carbon dioxide emissions. In addition, most 

alternative fuels are produced domestically, which 

is better for our economy, energy security and helps 

offset the cost of imported oil. 

The Clean Air Act also requires EPA to establish a 

national renewable fuel (RF) program. This program 

is designed to significantly increase the volume of 

renewable fuel that is blended into gasoline and diesel. 

Cleaner Trucks, Buses and 

“Nonroad” Equipment 

Diesel engines are more durable and are more fuel 

efficient than gasoline engines, but can pollute 

significantly more. Heavy-duty trucks and buses 

account for about one-third of nitrogen oxides 

emissions and one-quarter of particle pollution 

emissions from transportation sources. In some large 

cities, the contribution is even greater. Similarly, 

nonroad diesel engines such as construction and 

agricultural equipment emit large quantities of 

harmful particle pollution and nitrogen oxides, which 

contribute to ground-level ozone and other pervasive 

air quality problems. 

9
Cars, Trucks, Buses and, “Nonroad” Equipment 

Photo - Steve Delaney 

In the past, buses released large quantities of pollutants. Cleaner, 

less-polluting buses resulted from the 1990 Clean Air Act Amendments. 

EPA has issued rules to cut emissions from onroad 

and nonroad vehicles by more than 90 percent by 

combining stringent emissions standards for diesel 

engines and clean, ultra-low sulfur diesel fuel. 

Under the Clean Air Act, EPA is also addressing 

pollution from a range of nonroad sources, including 

locomotives and marine vessels, recreational vehicles, 

and lawn and garden equipment. Together these 

sources comprise a significant portion of emissions 

from the transportation sector. 

Transportation Policies 

Congress required “conformity” in the Clean Air Act 

Amendments of 1990. In other words, transportation 

projects such as construction of highways and transit 

rail lines cannot be federally funded or approved 

unless they are consistent with state air quality goals. 

In addition, transportation projects must not cause 

or contribute to new violations of the air quality 

standards, worsen existing violations, or delay 

attainment of air quality standards. 

The conformity provisions require areas that have 

poor air quality now, or had it in the past, to 

examine the long-term air quality impacts of their 

transportation system and ensure that it is compatible 

with the area’s clean air goals. In doing so, those areas 

must assess the impacts of growth on air pollution 

and decide how to manage growth. State and local 

agencies must work together to either change the 

transportation plan and/or the state air plan to 

achieve the necessary emission reductions. 

Inspection and Maintenance Programs 

Proper maintenance of a car’s engine and pollution 

control equipment is critical to reduce excessive air 

pollution. To help ensure that such maintenance 

occurs, the Clean Air Act requires certain areas with air 

pollution problems to run inspection and maintenance 

(I/M) programs. The 1990 Act also established the 

requirement that passenger vehicles be equipped 

with on board diagnostics. The diagnostics system is 

designed to trigger a dashboard “check engine” light 

alerting the driver of a possible pollution control device 

malfunction. To help ensure that motorists respond to 

the “check engine” light in a timely manner, the Act 

requires that I/M programs include an inspection of the 

on board diagnostic system. 

Interstate and International Air 

Pollution 

Air pollution does not recognize state or international 

boundaries. Pollutants can be carried long distances by 

the wind. Dirty air even turns up in places where you 

least expect it, like national parks or wilderness areas 

in remote parts of the United States. 

Taller smokestacks can lift pollutants high above 

a local community but help pollutants get into 

More cars driving more miles! This is 

why air pollution from cars has not 

improved as much as we had hoped, 

even though individual cars produce 

less pollution than they used to. 

10
wind currents that can carry them hundreds, even 

thousands, of miles. For example, emissions from 

power plants and industrial boilers can travel 

hundreds of miles and contribute to smog, haze, 

and air pollution in downwind states. One family 

of pollutants, nitrogen oxides, also reacts with other 

chemicals, sunlight and heat to form ground-level 

ozone. The nitrogen oxides and the ozone itself can be 

transported with the weather to help cause unhealthy 

air in cities and towns far downwind. 

States and tribes seeking to clean up air pollution are 

sometimes unable to meet EPA’s national standards 

because of pollution blowing in from other areas. The 

Clean Air Act has a number of programs designed to 

reduce long-range transport of pollution from one area 

to another. The Act has provisions designed to ensure 

that emissions from one state are not contributing 

to public health problems in downwind states. 

It does this, in part, by requiring that each state’s 

implementation plan contain provisions to prevent 

the emissions from the facilities or sources within its 

borders from contributing significantly to air pollution 

problems “downwind” – specifically in those areas that 

fail to meet EPA’s national air quality standards. If 

a state or tribe has not developed the necessary plan 

to address this downwind pollution, EPA can require 

the state to do so. If the state still does not take the 

necessary action, EPA can implement a federal plan to 

achieve the necessary emission reductions. 

Also, the Act gives any state or tribe the authority to 

ask EPA to set emission limits for specific sources of 

pollution in other (upwind) areas that significantly 

contribute to its air quality problems. States and tribes 

can petition EPA to require the upwind areas to reduce 

air pollution. 

The Act provides for interstate commissions to develop 

regional strategies for cleaning up air pollution. For 

instance, state and tribal governments from Maine to 

Virginia, the government of the District of Columbia, 

and EPA are working together through the Ozone 

Transport Commission (OTC) to reduce ground-level 

ozone along the east coast. 

The Clean Air Act also requires EPA to work with 

states to reduce the regional haze that affects visibility 

in 156 national parks and wilderness areas, including 

11

• 

has been found in fatty tissues of polar bears and 

• 

Over 

• 

Midwest contribute to acid rain, haze and particle 

Long Distances 

Toxaphene, a pesticide used in the U. S. corn belt 

other Arctic animals – thousands of miles from any 

possible source. 

Nitrogen oxides deposited from the air have 

contributed to fish kills by increasing the growth of 

oxygen-depleting algae in the Chesapeake Bay. 

a quarter of the nitrogen in the Bay and its tidal rivers 

and streams is estimated to come from air pollution 

carried by the wind from power plants and industrial 

sources far away. 

Emissions of sulfur oxides from power plants in the 

pollution problems in the eastern United States 

hundreds of miles away. 

Air Pollution Travels 

the Grand Canyon, Yosemite, the Great Smokies, and 

Shenandoah National Parks. During much of the year 

in these areas, a veil of white or brown haze hangs 

in the air blurring the view. Most of this haze is not 

natural. It is air pollution, carried by the wind often 

many hundreds of miles from where it originated. 

Under the regional haze provisions of the Clean Air 

Act, the states and tribes, in coordination with the 

EPA, the National Park Service, U.S. Fish and Wildlife 

Service, the U.S. Forest Service, and others, develop 

and implement air quality protection plans to reduce 

the pollution that causes visibility impairment. EPA 

has worked with states and tribes across the country to 

form Regional Planning Organizations to develop plans 

to reduce pollutants that cause haze. 

Interstate and International Air Pollution 
Clearing the Air in Our National Parks


Yellowstone


poor 

You might not expect air pollution in our 

national parks, especially since many 

are far from big cities and polluting 

industries. However, air pollution carried 

far from its sources has caused major 

reduction in visibility in some of our 

best-loved national parks. The Clean Air 

Act has provisions for reducing "regional 

haze," air pollution that reduces visibility 

in the national parks. To learn more, visit 

www.epa.gov/visibility. 

These photos show how good and bad 

the visibility can be at national parks 

from coast to coast. You can see realtime pictures of visibility at several 

national parks by visiting the National 

Park Service Website, www.nps.gov. 

Air resource specialists at the national 

parks—rangers who specialize in air 

pollution—present visitor programs, 

participate in air pollution monitoring 

and research, and provide information to 

visitors interested in air quality. 

good 

Rocky Mountains 

poor 

good 

Big Bend 

poor 

good 

Photos - National Park Service and 

Colorado State University 

12
Acadia


poor 

good 

Shenandoah 

poor 

good 

Great Smoky Mountains 

poor 

good 

13
Reducing Acid Rain 

Reducing Acid Rain 

But you may 

acidic pollution such as acid gas and acid dust. All 

Acid 

an acid. 

or fog. 

may fall to Earth in gases or particles. 

Sulfur dioxide (SO2 x

SO2 

and NOx

vapor and other chemicals to form acids that fall back to 

Earth. 

How Acid Rain is Formed 

These 

by wind. 

pollutants fall to Earth in wet form (acid rain, 

or dusts). 

You have probably heard of "acid rain." 

not have heard of other forms of acid precipitation 

such as acid snow, acid fog or mist, or dry forms of 

of these can be formed in the atmosphere and fall to 

Earth causing human health problems, hazy skies, 

environmental problems and property damage. 

precipitation is produced when certain types of air 

pollutants mix with the moisture in the air to form 

These acids then fall to Earth as rain, snow, 

Even when the weather is dry, acid pollutants 

) and nitrogen oxides (NO ) are the 

principal pollutants that cause acid precipitation. 

 emissions released to the air react with water 

Power plants burning coal and heavy oil produce 

Burning fuels release acid pollutants. 

pollutants are carried far from their sources 

Depending on the weather, the acid 

snow, mist or fog) or in dry form (acid gases 

over two-thirds of the annual SO2 emissions in the 

United States. The majority of NOx (about 50 percent) 

comes from cars, buses, trucks, and other forms of 

transportation. About 40 percent of NOx emissions are 

from power plants. The rest is emitted from various 

sources like industrial and commercial boilers. 

Heavy rainstorms and melting snow can cause 

temporary increases in acidity in lakes and streams, 

primarily in the eastern United States. The temporary 

increases may last for days or even weeks, causing 

harm to fish and other aquatic life. 

The air pollutants that cause acid rain can do more 

than damage the environment—they can damage our 

health. High levels of SO2 in the air aggravate various 

lung problems in people with asthma and can cause 

breathing difficulties in children and the elderly. In 

some instances, breathing high levels of SO2 can even 

damage lung tissue and cause premature death. 

Acid Rain’s Harmful Effects

Acid lakes and streams have been found all over the Acid rain has damaged trees in the mountains of Vermont 

country. For instance, lakes in Acadia National Park and other states. Red spruce trees at high altitudes 

on Maine’s Mt. Desert Island have become acidic due appear to be especially sensitive to acid rain. The 

to pollution from the midwest and the east coast. pollutants that cause acid rain can make the air hazy or 

Streams in Maryland and West Virginia, as well as foggy; this occurs in the eastern United States in areas 

lakes in the Upper Peninsula of Michigan, have been like the Great Smokies and Shenandoah National Park, 

damaged by acid rain. Since the wind can carry areas where vacationers go to enjoy the beautiful scenery 

pollutants across the country, the effects of acid rain and awe-inspiring views. In addition to damaging the 

can be seen far from the original source of the acid- natural environment, acid rain can damage manmade 

forming pollutant. objects such as stone statues, buildings, and monuments. 

14
The 1990 changes to the Clean Air Act introduced a 

nationwide approach to reducing acid pollution. The 

law is designed to reduce acid rain and improve public 

health by dramatically reducing emissions of sulfur 

dioxide (SO2) and oxides of nitrogen (NOx). Using 

a market-based cap and trade approach, the program 

sets a permanent cap on the total amount of SO2 that 

may be emitted by electric power plants nationwide. 

As of 2005, emission reductions were more than 7 

million tons from power plants, or 41 percent below 

1980 levels. 

The initial phase of EPA’s Acid Rain Program went 

into effect in 1995. The law required the highest 

emitting units at 110 power plants in 21 Midwest, 

Appalachian, and Northeastern states to reduce 

emissions of SO2. The second phase of the program 

went into effect in 2000, further reducing SO2 

emissions from big coal-burning power plants. Some 

smaller plants were also included in the second phase 

of the program. Total SO2 releases for the nation’s 

power plants are permanently limited to the level set 

by the 1990 Clean Air Act — about 50 percent of the 

levels emitted in 1980. 

Each allowance is worth one ton of SO2 emissions 

released from the plant’s smokestack. Plants 

may only release the amount of SO2 equal to the 

allowances they have been issued. If a plant expects 

to release more SO2 than it has allowances, it has 

to purchase more allowances or use technology and 

other methods to control emissions. A plant can buy 

allowances from another power plant that has more 

allowances than it needs to cover its emissions. 

There is an allowances market that operates like the 

stock market, in which brokers or anyone who wants to 

take part in buying or selling allowances can participate. 

Allowances are traded and sold nationwide. 

EPA’s Acid Rain Program has provided bonus 

allowances to power plants for installing clean coal 

technology that reduces SO2 releases, using renewable 

energy sources (solar, wind, etc.), or encouraging 

energy conservation by customers so that less 

power needs to be produced. EPA has also awarded 

allowances to industrial sources voluntarily entering 

the Acid Rain Program. 

15

The 1990 Clean Air Act has stiff monetary penalties 

for plants that release more pollutants than are covered 

by their allowances. All power plants covered by the 

Acid Rain Program have to install continuous emission 

monitoring systems, and instruments that keep track 

of how much SO2 and NOx the plant’s individual units 

are releasing. Power plant operators keep track of this 

information hourly and report it electronically to EPA 

four times each year. EPA uses this information to 

make sure that the plant is not releasing quantities of 

pollutants exceeding the plant’s allowances. A power 

plant’s program for meeting its SO2 and NO limits x

will appear on the plant’s permit, which is filed with 

the state and EPA and is available for public review. 

You can also help to reduce SO2 and NO emissions x

from power plants by conserving energy and 

promoting conservation and renewable energy 

efficiency in your community. Check www.epa.gov/air/ 

actions/at_home.html for energy conservation tips. 

Market Approaches and Economic 

Incentives 

Besides the ground-breaking features in the Acid Rain 

Program, the 1990 Clean Air Act encouraged other 

innovative approaches that spur technology. These 

approaches allow businesses greater flexibility in 

how they comply with the law, and thus clean-up air 

pollution as efficiently and inexpensively as possible. 

For example: 

■ EPA’s new cleaner vehicle standards include an 

averaging system that allows manufacturers to 

choose how to produce a mix of more- or lesspolluting vehicles, as long as the overall fleet 

average is lower. 

■ Gasoline refiners can receive credits if they produce 

cleaner gasoline than required, and they use those 

credits when their gasoline does not quite meet the 

clean-up requirements. 

Reducing Acid Rain 
Reducing Toxic Air Pollutants 

Reducing Toxic Air Pollutants 

Toxic air pollutants, or air toxics, are known to cause 

or are suspected of causing cancer, birth defects, 

reproduction problems, and other serious illnesses. 

Exposure to certain levels of some toxic air pollutants 

can cause difficulty in breathing, nausea or other 

illnesses. Exposure to certain toxic pollutants can 

even cause death. 

Some toxic air pollutants are of concern because 

they degrade slowly or not at all, as in the case of 

metals such as mercury or lead. These persistent air 

toxics can remain in the environment for a long time 

and can be transported great distances. Toxic air 

pollutants, like mercury or polychlorinated biphenyls, 

deposited onto soil or into lakes and streams persist 

and bioaccumulate in the environment. They can 

affect living systems and food chains, and eventually 

affect people when they eat contaminated food. This 

can be particularly important for American Indians 

or other communities where cultural practices or 

subsistence life styles are prevalent. 

The majority of air toxics come from manmade 

sources, such as factory smokestack emissions and 

motor vehicle exhaust. 

Gasoline also contains air toxics. When you put fuel in 

your car, gases escape and form a vapor. You can smell 

these vapors when you refuel your vehicle. 

When cars and trucks burn gasoline, toxic air 

pollutants are emitted from the tailpipe. Those air 

toxics are combustion products—chemicals that are 

produced when gasoline is burned. EPA is working 

with industries to develop cleaner-burning fuels and 

more efficient engines, and is taking steps to make 

sure that pollution control devices installed in motor 

vehicles work properly. EPA has issued requirements 

that are leading to cleaner-burning diesel engines, 

reducing releases of particle pollution and air toxics. 

Air toxics are also released from industrial sources, 

such as chemical factories, refineries, and incinerators, 

and even from small industrial and commercial 

sources, such as dry cleaners and printing shops. 

Under the 1990 Clean Air Act, EPA has regulated both 

large and small sources of air toxics, but has mainly 

focused efforts on larger sources. 

Before the 1990 Clean Air Act Amendments, EPA 

regulated air toxics one chemical at a time. This 

Persistent Bioaccumulative 

ported in the wind can be just as toxic 10,000 miles away 

chain, harming fish-eating animals and people. Small fish 

may consume plants that live in water contaminated by 

levels go up. So a large fish consumed by people may have 

in big fish to levels thousands of times the levels found in 

Those 

Toxics (PBTs) 

PBTs such as mercury and DDT last for a long time in the 

environment with little change in their structure or toxic 

effects. This means that a persistent toxic chemical transas it was at the smokestack from which it was released. 

Some PBTs, such as polychlorinated biphenyls (PCBs), 

have been found in remote parts of the Arctic, far away 

from the industrial sources that produce them. 

Some of the PBTs that move through the air are deposited 

into water bodies and are concentrated up through the food 

PBTs, which are absorbed into plant tissues. Big fish eat 

smaller fish and as the PBTs pass up the food chain, their 

a much higher concentration of PBTs in its tissues than the 

simple plant first absorbing the PBTs. PBTs can concentrate 

the contaminated water. 

Over 2000 U.S. water bodies are covered by fish consumption advisories, warning people not to eat the fish because 

of contamination with chemicals, usually PBTs. 

compounds have been linked to illnesses such as cancer, 

birth defects, and nervous system disorders. 

The 1990 Clean Air Act gave EPA the authority to reduce 

PBT levels by requiring pollution sources to install control 

devices or change production methods. 

approach did not work well. Between 1970 and 1990, 

EPA established regulations for only seven pollutants. 

The 1990 Clean Air Act Amendments took a completely 

different approach to reducing toxic air pollutants. The 

Amendments required EPA to identify categories of 

industrial sources for 187 listed toxic air pollutants and 

to take steps to reduce pollution by requiring sources 

to install controls or change production processes. It 

makes good sense to regulate by categories of industries 

rather than one pollutant at a time, since many 

individual sources release more than one toxic chemical. 

Developing controls and process changes for industrial 

source categories can result in major reductions in 

releases of multiple pollutants at one time. 

16
EPA has published regulations covering a wide range 

of industrial categories, including chemical plants, 

incinerators, dry cleaners, and manufacturers of wood 

furniture. Harmful air toxics from large industrial 

sources, such as chemical plants, petroleum refineries, 

and paper mills, have been reduced by nearly 70 

percent. These regulations mostly apply to large, 

so-called "major" sources and also to some smaller 

sources known as "area" sources. In most cases, EPA 

does not prescribe a specific control technology, but 

sets a performance level based on a technology or 

other practices already used by the better-controlled 

and lower emitting sources in an industry. EPA works 

to develop regulations that give companies as much 

flexibility as possible in deciding how they reduce 

their toxic air emissions—as long as the companies 

meet the levels required in the regulations. 

The 1990 Clean Air Act requires EPA to first set 

regulations using a technology-based or performancebased approach to reduce toxic emissions from 

industrial sources. After EPA sets the technologybased regulations, the Act requires EPA to evaluate 

any remaining ("residual") risks, and decide whether 

it is necessary to control the source further. That 

assessment of remaining risk was initiated in the 

year 2000 for some of the industries covered by the 

technology-based standards. 

Chemical Emergencies 

of highly toxic chemicals. 

The 1990 Act also established the Chemical Safety 

investigates airplane and train crashes. The Chemical 

determine how and why an accident involving toxic 

chemicals happened. The goal is to apply understandtoxic chemicals. 

The 1984 chemical disaster that resulted in thousands 

of deaths in Bhopal, India, inspired sections of the 1990 

Clean Air Act that require factories and other businesses to develop plans to prevent accidental releases 

Board, an independent agency that investigates and 

reports on accidental releases of toxic chemicals from 

industrial facilities. The Board operates much like the 

National Transportation Safety Board, the agency that 

Safety Board assembles the information necessary to 

ing of accidents to prevent other accidents involving 

17

Air Toxics and Risk 

The Clean Air Act requires a number of studies to help 

EPA better characterize risks to human health and the 

environment from air toxics. Those studies provide 

information for rulemaking and support national 

and local efforts to address risks through pollution 

prevention and other voluntary programs. Among 

these risk reduction initiatives are: 

■ The Integrated Urban Air Toxics Strategy includes 

local and community-based initiatives to reduce local 

toxic air emissions. The primary goal of the strategy 

is to reduce public health risks from both indoor 

and outdoor sources of toxic air pollutants. More 

information can be found at www.epa.gov/ttn/atw. 

■ The Great Waters Program incorporates activities 

to investigate and reduce the deposition of toxic 

air pollutants to the "Great Waters," which include 

the Chesapeake Bay, Lake Champlain, the Great 

Lakes, National Estuary Program areas, and National 

Estuarine Research Reserves. To learn more, visit 

www.epa.gov/glnpo. 

■ Initiatives targeting emission reductions of persistent 

bioaccumulative toxics (PBTs) like mercury, DDT (a 

pesticide banned in the United States), and dioxins. 

Protecting the Stratospheric 

Ozone Layer 

Ozone can be good or bad depending on where 

it is located. Close to the Earth’s surface, groundlevel ozone is a harmful air pollutant. Ozone in the 

stratosphere, high above the Earth, protects human 

health and the environment from the sun’s harmful 

ultraviolet radiation. This natural shield has been 

gradually depleted by manmade chemicals. So in 

1990, Congress added provisions to the Clean Air Act 

for protecting the stratospheric ozone layer. 

Ozone in the stratosphere, a layer of the atmosphere 

located 10 to 30 miles above the Earth, serves as a 

shield, protecting people and the environment from the 

sun’s harmful ultraviolet radiation. The stratospheric 

ozone layer filters out harmful sun rays, including a type 

of sunlight called ultraviolet B. Exposure to ultraviolet 

B (UVB) has been linked to cataracts (eye damage) and 

skin cancer. Scientists have also linked increased UVB 

exposures to crop injury and damage to ocean plant life. 

Protecting the Stratospheric Ozone Layer 
Protecting the Stratospheric Ozone Layer 

In the mid-1970s, scientists became concerned that 

chlorofluorocarbons (CFCs) could destroy stratospheric 

ozone. At that time, CFCs were widely used as aerosol 

propellants in consumer products such as hairsprays 

and deodorants, and as coolants in refrigerators and 

air conditioners. In 1978, the U.S. government banned 

CFCs as propellants in most aerosol uses. 

Scientists have been monitoring the stratospheric 

ozone layer since the 1970s. In the 1980s, scientists 

began accumulating evidence that the ozone layer 

was being depleted. The ozone hole in the region of 

the South Pole, which has appeared each year during 

the Antarctic winter (our summer), often is bigger 

than the continental United States. Between 1978 and 

1997, scientists have measured a 5 percent loss of 

stratospheric ozone—a significant amount. 

Over 190 countries, including the major industrialized 

nations such as the United States, have signed the 

1987 Montreal Protocol, which calls for elimination of 

chemicals that destroy stratospheric ozone. Countries 

that signed the Protocol are committed to limiting the 

production and use of those chemicals. 

The 1990 Clean Air Act required EPA to set up a 

program for phasing out production and use of ozonedestroying chemicals. In 1996, U.S. production 

ended for many of the chemicals capable of doing the 

most serious harm such as CFCs, halons, and methyl 

chloroform. 

Photo - Steve Delaney 

Service stations must have special equipment that prevents 

release of refrigerant chemicals to the air when they 

are recharging car air conditioning systems. 

OZONE HOLE (

ozone layer) 

thin spot in protective 

When the protective ozone layer is damaged, there is an increase in 

harmful rays from the sun reaching the Earth. These rays can harm 

both health and the environment. 

Unfortunately, it will be about 60 years before the 

stratospheric ozone layer heals. Because of the ozonedestroying chemicals already in the stratosphere 

and those that will arrive within the next few years, 

stratospheric ozone destruction will likely continue 

throughout the decade. September 24, 2006, tied for 

the largest ozone hole on record at 29 million square 

kilometers (11.4 million square miles). The year 2006 

also saw the second largest sustained ozone hole. 

The Clean Air Act includes other steps to protect the 

ozone layer. The Act encourages the development 

of "ozone-friendly" substitutes for ozone-destroying 

chemicals. Many products and processes have been 

reformulated to be more "ozone-friendly." For 

instance, refrigerators no longer use CFCs. 

Sometimes it isn’t easy to phase out an ozonedestroying chemical. For instance, substitutes have 

not been found for CFCs used in certain medical 

applications. The limit on the production of methyl 

bromide, a pesticide, was extended because farmers 

did not yet have an effective alternative. Despite the 

inevitable delays because of technical and economic 

concerns, ozone-destroying chemicals are being 

phased out, and, with continued work, over time the 

protective ozone layer will be repaired. 

18
How Ozone Holes 

the layer of stratospheric ozone that 

Are Formed 

Ozone-destroying chemicals 

escape into the air and reach the 

stratosphere. Over time they reduce 

protects us. 

Permits and Enforcement 

Permits 

One of the major initiatives Congress added to the 

Clean Air Act in 1990 is an operating permit program 

for larger industrial and commercial sources that 

release pollutants into the air. Operating permits 

include information on which pollutants are being 

released, how much may be released, and what kinds 

of steps the source’s owner or operator is required to 

take to reduce the pollution. Permits must include 

plans to measure and report the air pollution emitted. 

States and tribes issue operating permits. If those 

governments do not do a satisfactory job of carrying 

out the Clean Air Act permitting requirements, EPA 

can take over issuing permits. 

Operating permits are especially useful for businesses 

covered by more than one part of the Clean Air Act 

and additional state or local requirements, since 

information about all of a source’s air pollution is 

in one place. The permit program simplifies and 

clarifies businesses’ obligations for cleaning up air 

pollution and can reduce paperwork. For instance, 

an electric power plant may be covered by the acid 

rain, toxic air pollutant, and smog (ground-level 

ozone) sections of the Clean Air Act. The detailed 

information required by those separate sections is 

consolidated into one place in an operating permit. 

Thousands of operating permits that have been 

issued across the United States are available to the 

public. Contact your state or regional air pollution 

control agency or EPA for information on access to 

those documents. 

Businesses seeking permits have to pay permit fees, 

much like car owners paying for car registrations. 

These fees pay for the air pollution control activities 

related to operating permits. 

Enforcement 

The Clean Air Act gives EPA important enforcement 

powers. In the past, it was difficult for EPA to 

penalize a company for violating the Clean Air 

Act–the Agency had to go to court for even minor 

violations. The 1990 Amendments strengthened 

EPA’s power to enforce the Act, increasing the range 

of civil and criminal sanctions available. In general, 

when EPA finds that a violation has occurred, the 

agency can issue an order requiring the violator to 

comply, issue an administrative penalty order (use 

EPA administrative authority to force payment of 

a penalty), or bring a civil judicial action (sue the 

violator in court). 

19
Public Participation 

Public Participation 

Public participation is a very important part of the 

1990 Clean Air Act. Throughout the Act, different 

provisions give the public opportunities to take part in 

determining how the law is carried out. 

Often, when EPA is working on a major rule, the 

Agency will hold hearings in various cities across the 

country, at which the public can comment. You can 

also submit written comments directly to EPA for 

inclusion in the public record associated with that rule. 

Or, for instance, you can participate in development 

of a state or tribal implementation plan. Commenting 

on a state or tribal plan could be worthwhile since 

approaches for cleaning up pollution could have direct 

effects on the way you and your family live. 

The 1990 Clean Air Act gives you opportunities to 

take direct action to get pollution cleaned up in your 

community. You can get involved in reviewing air 

pollution permits for industrial sources in your area. 

You also can ask EPA, your state or tribe to take action 

against a polluter, and, in some cases, you may be 

able to take legal action against a source’s owner or 

operator. 

Reports required by the 1990 Clean Air Act are 

usually available to the public. Those reports include 

a great deal of information on how much pollution 

is being released by industrial and commercial 

sources. Monitoring data collected by EPA, states and 

tribes that measure the level of selected pollutants 

in a community’s air are also available to the public. 

Information on air emissions and monitoring data can 

be found at: www.epa.gov/airtrends. 

This site contains 

information about the air quality in your 

on topics such as: commonly found 

air pollutants, transportation pollution 

stratospheric ozone depletion. 

Learn More About Clean 

Air Act Programs 

To learn more about air quality, visit 

www.epa.gov/air. 

community and provides information 

programs, air toxics, acid rain, and 

20 
How the Clean Air 

well the Clean Air Act is working. Over 

time, the Clean Air Act will continue to 

their full impact. 

installed. On the other hand, in the case of cars and 

trucks, it may take several years for old vehicles to be 

up cars and trucks will be seen. 

T

Act Is Working 

here are several ways you can tell how 

reduce air pollution, but it will take time 

for some of the Act’s provisions to have 

In general, when EPA or state, local, and tribal 

governments require sources of pollution to adopt 

control measures, you will see results right away. For 

instance, when large industrial facilities are required 

to install pollution control equipment, releases 

of pollutants should drop when the equipment is 

retired from the road before the full effects of cleaning 

You can also check on how individual facilities are 

meeting their clean-up requirements. Air pollutant 

releases at individual facilities such as power plants 

are set out in the facility’s permit, which you can 

review. This document provides information on state, 

local, or tribal air pollution control agencies that can 

give you more information on how to get access to 

permits. (See page 23.) 

Monitoring air quality is the best way to tell if the air is 

getting cleaner, because the monitors accurately report 

how much of a pollutant is in the air. You can request 

EPA, state, local, or tribal monitoring reports that show 

changes over time. It is updated frequently, so you can 

get recent information on what’s happening to the air 

in your community. Visit www.epa.gov/airtrends for 

more information. 

The "Air Quality Index" (AQI) is a "public-friendly" 

way of using actual monitoring data to help us assess 

how clean our air is. Americans are familiar with 

many radio, TV, and newspaper weather forecasters 

talking about the AQI— telling you that the air is 

so polluted that a "Code Orange" or "Code Red" air 

quality condition is in effect. The AQI tracks pollution 

for your local area. The color codes, which range 

from green to purple, correspond to specific pollution 

levels. As clean-up programs are implemented for the 

air pollutants tracked by the AQI, we hope to see a 

reduction in the number of Code Orange and Code 

Red air quality days. Information on the AQI can be 

found at: www.airnow.gov. 

The National Air Toxics Assessment is an on-going, 

comprehensive evaluation of air toxics in the United 

States. Visit www.epa.gov/ttn/atw for air toxics 

information on emissions, risk, and exposure in 

your area. 

How the Clean Air Act Is Working 

21 
22 

Air Pollution 

ideas that you can take to help clean our 

At Home 

■

■

■

gov/woodstoves. 

■

■

■ Connect your outdoor lights to a timer or use 

solar lighting. 

■

hot. 

■ Lower the thermostat on your water heater to 

120°F. 

■

finishes, and paint strippers. 

■

radioactive gas that is odorless and tasteless. 

If the test shows elevated levels of radon, the 

epa.gov/radon. 

■ Choose not to smoke in your home, especially if 

Buy Smart 

■

W

Ways to Reduce Air Pollution 

Ways to Reduce 

e make choices everyday that can help 

reduce air pollution. Below are a few 

air. 

 Conserve energy – turn off appliances and lights 

when you leave the room. 

 Recycle paper, plastic, glass bottles, cardboard, 

and aluminum cans. (This conserves energy and 

reduces production emissions.) 

 Keep woodstoves and fireplaces well maintained. 

You should also consider replacing old wood 

stoves with EPA-certified models. Visit www.epa. 

 Plant deciduous trees in locations around your 

home to provide shade in the summer, but to 

allow light in the winter. 

 Buy green electricity–produced by low–or even 

zero-pollution facilities. 

 Wash clothes with warm or cold water instead of 

 Use low-VOC or water-based paints, stains, 

 Test your home for radon–a dangerous, 

problem can be fixed cost effectively. Visit www. 

you have children. If you or your visitors must 

smoke, then smoke outside. Visit www.epa.gov/ 

smokefree. 

 Buy ENERGY STAR products, including energy 

efficient lighting and appliances. They are 

environmentally friendly products. For more 

information, visit www.energystar.gov or call 

1-888-STAR-YES. 

■ Choose efficient, low-polluting models of 


vehicles. Visit www.epa.gov/greenvehicles.


■ Choose products that have less packaging and 

are reusable. 

■ Shop with a canvas bag instead of using paper 

and plastic bags. 

■ Buy rechargeable batteries for devices used 


frequently.


Drive Wise 

Plan your trips. Save gasoline and reduce air 

pollution. 

■ Keep tires properly inflated and aligned. 

■ In the summertime, fill gas tank during cooler 

evening hours to cut down on evaporation. 

Avoid spilling gas and don't “top off” the tank. 

Replace gas tank cap tightly. 

■ Avoid waiting in long drive-thru lines, for 

example, at fast-food restaurants or banks. Park 

your car and go in. 

■ When possible, use public transportation, walk, 

or ride a bike. 

■ Get regular engine tune ups and car maintenance 

checks (especially for the spark plugs). 

■ Use an energy-conserving (EC) grade motor oil. 

■ Ask your employer to consider flexible work 

schedules or telecommuting. 

■ Report smoking vehicles to your local air agency. 

■ Join a carpool or vanpool to get to work. 

For Your Health 

■ Check daily air quality forecasts, which tell how 

clean or polluted your air is, and the associated 

health concerns. Visit www.airnow.gov. 

■ Remove indoor asthma triggers from your home 

and avoid outdoor triggers in order to effectively 

control your asthma. Visit www.epa.gov/asthma 

to learn more about asthma triggers and ways to 

avoid them. 

■ Minimize your sun exposure. Wear sun block 

and UV protection sunglasses. To find out about 

current forecasts of UV where you live, go to 

www.epa.gov/sunwise/uvindex.html. 
State and Tribal

Contact Information 

For more information on state and territorial air 

pollution control agencies, visit www.4cleanair.org. 

For more information on tribal air pollution control 

agencies, visit www.epa.gov/oar/tribal or 

www.ntaatribalair.org. 

EPA Regional Offices

Region 1 

(Connecticut, Maine, Massachusetts, New

 Hampshire, Rhode Island, Vermont) 

1 Congress Street, Suite 1100 

Boston, MA 02114-2023 

Phone: 888-372-7341 (Inside Region I) 

Phone: 617-918-1111 (Outside Region II) 

Web Site: www.epa.gov/region1 

Region 2 

(New Jersey, New York, Puerto Rico, Virgin Islands) 

290 Broadway, 26th Floor 

New York, NY 10007-1866 

Phone: 212-637-3000 

Web Site: www.epa.gov/region2 

Region 3 

(Delaware, Maryland, Pennsylvania, Virginia, West

 Virginia, District of Columbia) 

1650 Arch Street 

Philadelphia, PA 19103-2029 

Phone: 800-438-2474 (Inside Region 3) 

Phone: 215-814-2100 (Outside Region 3) 

Web Site: www.epa.gov/region3 

Region 4 

(Alabama, Florida, Georgia, Kentucky, Mississippi,

 North Carolina, South Carolina, Tennessee) 

Atlanta Federal Center 

61 Forsyth Street, SW 

Atlanta, GA 30303-3104 

Phone: 404-562-9900 

Phone: 1-800-241-1754 (Toll-free) 

Web Site: www.epa.gov/region4 

23

Region 5 

(Illinois, Indiana, Michigan, Minnesota, Ohio, 

 Wisconsin) 

77 W. Jackson Boulevard 

Chicago, IL 60604 

Phone: 800-621-8431 (Inside Region 5) 

Phone: 312-353-2000 (Outside Region 5) 

Web Site: www.epa.gov/region5 

Region 6 

(Arkansas, Louisiana, New Mexico, Oklahoma,

 Texas) 

1445 Ross Avenue, 7th Floor, Suite 1200 

Dallas, TX 75202-2733 

Phone: 214-665-6444 

Web Site: www.epa.gov/region6 

Region 7 

(Iowa, Kansas, Missouri, Nebraska) 

901 N 5th Street 

Kansas City, KS 66101 

Phone: 800-223-0425 (Toll free) 

Phone: 913-551-7003 

Web Site: www.epa.gov/region7 

Region 8 

(Colorado, Montana, North Dakota, South Dakota,

 Utah, Wyoming) 

999 18th Street, Suite 300 

Denver, CO 80202-2466 

Phone: 800-227-8917 (Inside Region 8) 

Phone: 303-312-6312 (Outside Region 8) 

Web Site: www.epa.gov/region8 

Region 9 

(Arizona, California, Hawaii, Nevada, and Pacific

 Islands, Tribal Nations subject to U.S. law) 

75 Hawthorne Street 

San Francisco, CA 94105 

Phone: 415-744-1500 

Web Site: www.epa.gov/region9 

Region 10 

(Alaska, Idaho, Oregon, Washington) 

1200 6th Avenue 

Seattle, WA 98101 

Phone: 206-553-1200 

Web Site: www.epa.gov/region10 

Contact Information 
United States Office of Air Quality Planning and Standards Publication No. EPA-456/K-07-001 

Environmental Protection Research Triangle Park, NC April 2007 

Agency