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Frequently Asked Questions (FAQs)
Q: What is acid rain?
A: "Acid rain" is a broad term used to describe several ways that
acids fall out of the
atmosphere. A more precise term is acid deposition, which has two parts:
wet (rain,
fog, and snow) and dry (particles and gases). Acid rain's effects include:
- harming fish and other organisms living in lakes
and streams
- harming to a variety of plants and animals on
land
- damaging human health
- reducing how clearly we see through the air
- damaging to materials like those found in statues
and buildings.
The specific effects and their severity depends on several factors, including
soil and surface water chemistry, the amount of air pollution that creates
acid rain, and the specific species involved. For more information, see
the acid rain home page.
Q: What is the difference between air pollutants and toxic air pollutants?
A: Toxic air pollutants (or
Hazardous Air Pollutants, HAPs) are different from air pollutants. Air
toxics are known or suspected to cause cancer or other serious heath effects,
such as damage to respiratory or nervous systems. Toxic air pollutants
may exist as particulate matter or as vapors (gases). Air toxics include
metals, particles, and certain vapors from fuels and other sources. To
find out more about toxic air pollutants visit the basic facts page.
Q: What causes indoor air quality problems and how can I tell whether
I have a problem?
A: Indoor pollution
sources that release gases or particles into the air are the primary
cause of indoor air quality problems in homes. Inadequate ventilation
can increase indoor pollutant levels by not bringing in enough outdoor
air to dilute emissions from indoor sources and by not carrying indoor
air pollutants out of the home. High temperature and humidity levels can
also increase concentrations of some pollutants. EPA has developed a Building Survey
to help you determine if there's a problem.
Q: What are the two main issues related to ozone?
A: Ozone, a molecule with three oxygen atoms, is at the core
of two very different issues: stratospheric ozone depletion and ground-level
ozone formation.
Stratospheric Ozone Depletion
About 90% of all ozone occurs in the ozone layer, a region of high concentrations
approximately 15-40 kilometers (10-25 miles) above the Earth's surface,
in the stratosphere. The ozone layer protects all life from ultraviolet
radiation (UV) from the sun. Unfortunately, several chemicals used in
air conditioning and certain industrial uses damage the ozone layer, allowing
more UV to reach the Earth's surface. Since UV causes skin cancer, cataracts,
and other harmful
effects, ozone depletion will lead to increases in these problems.
Increased UV can also lead to reduced crop yield and disruptions in the
marine food chain. The ozone depletion
web site explains EPA's programs to protect the ozone layer and other
information related to ozone depletion. In particular, the ozone science page
offers much more detail on ozone depletion, its causes and effects, and
what the world is doing to fix the problem.
Ground-Level Ozone Formation
The same ozone molecules that protect us from UV high in the stratosphere
can cause health problems for people and animals when they form near the
Earth's surface. Ground-level ozone is formed when vehicle exhaust and
some other chemicals commonly used in industry mix in strong sunlight.
When these ozone concentrations get high enough, they can make breathing
difficult, especially for people with asthma and other respiratory diseases.
EPA's ozone mapping site provides information
on ozone levels in many US cities. If you hear an ozone alert on the news,
it means ozone levels in your area are very high that day, and you should
try to stay indoors and not exercise vigorously until ozone levels drop
again. EPA has several programs to reduce air pollution and ozone concentrations.
"Ozone: Good Up High,
Bad Nearby" is an EPA fact sheet that explains the difference between
"good" ozone (stratospheric) and "bad" ozone (ground-level) in more detail.
Q: What can be done to prevent pollution?
A: Did you know that your home and office contribute to the
greenhouse effect?
Energy used in our everyday activities -- turning on electrical appliances,
driving cars, and heating and cooling our homes -- is responsible for
air pollution that contributes to climate change. Technologies are available
today that can cut this energy use significantly and, at the same time,
improve our quality of life.
Preventing pollution is as easy as looking for the ENERGY STAR 
Label.
ENERGY STAR is already helping American homes, businesses, state and local
governments and other organizations by reducing energy consumption, emissions
of greenhouse gases and other harmful pollutants, and their associated
energy costs.
Other things you can do:
- Make sure your computer and monitor power management settings are
optimized, so they go into sleep mode when you're away from your desk
- Make sure someone in your office turns off the printer and copier
at the end of the day
- Set your printers and copiers to automatically print on both sides
-- it takes more energy to make a sheet of paper than to copy an image
onto it
For more information on Atmospheric Pollution Prevention Division's
mission, click
here.
Q: What is the definition for radiation?
A: Radiation
is energy given off by atoms in the form of particles or electromagnetic
rays. There are actually many different types of electromagnetic radiation
that have a range of energy levels. They form the electromagnetic spectrum
and include radio and microwaves, heat, light, and x-rays.
FAQs Pages:
Common Questions,
Clear Answers
Q: What pollutants affect air quality?
A: A few air pollutants, called criteria air
pollutants, are common throughout the United States. These pollutants
can injure health, harm the environment and cause property damage. The
current criteria pollutants are: Carbon Monoxide (CO), Lead (Pb), Nitrogen
Dioxide (NO2), Ozone (O3), Particulate matter with aerodynamic size less
than or equal to 10 micrometers (PM-10), and Sulfur Dioxide (SO2). To
find out more in depth information about the criteria air pollutants,
visit the Green
Book site.
Q: What kinds of air pollution are produced by mobile sources?
A: Combustion of fuels can cause the release of hydrocarbons (HC), carbon monoxide (CO), oxides of nitrogen (NOx),
particulate matter (PM), toxics, sulfur dioxide (SO2), and greenhouse
gases such as carbon dioxide
(CO2) and nitrous oxide (N2O). Mobile sources produce air pollution
from exhaust emissions, as well as evaporative emissions and refueling
losses from gasoline engines. The type and amount of pollution depends
on many factors: the type of engine or vehicle (e.g., passenger car, heavy-duty
truck, lawn mower, locomotive, etc.); the type of fuel used (e.g., gasoline,
diesel, or alternative fuels); the type and condition of emission control
devices (e.g., catalytic converters); and how the engine is used/run.
For example, diesel engines used in trucks, buses, locomotives, and ships
tend to emit more NOx and PM than gasoline engines. Engines with catalytic
converters (e.g., passenger cars) emit much less HC, CO, NOx, and toxics
than similar engines without catalysts (i.e., the catalytic converter
is an important pollution control device to reduce exhaust emissions).
Additional information on air pollution from mobile sources is available
on the Office of Mobile
Sources Web site.
Q: How is pollution affecting what we see?
A:Visibility impairment occurs as a result of the scattering and
absorption of light by particles and gases in the atmosphere. It is most
simply described as the haze which obscures the clarity, color, texture,
and form of what we see. The same particles which are linked to serious
health effects [sulfates, nitrates, organic carbon, soot (elemental carbon),
and soil dust] can significantly affect our ability to see.
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