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Ozone Pollution
How Ozone Pollution Works
BY CRAIG FREUDENRICH,
PH.D.
The
weather report on the radio or TV tells you that it is going to be
sunny and hot and that an orange ozone
alert has been issued.
What
is ozone? What does an orange alert mean? Why should you be concerned about it?
In
this article, we will examine what ozone is, how it is produced, what health
hazards it poses and what you can do to reduce ozone pollution.
Ozone is
a molecule of three oxygen atoms bound together (O3).
It
is unstable and highly reactive.
Ozone
is used as a bleach, a deodorizing agent, and a sterilization agent for air and
drinking water. At low concentrations, it is toxic.
Ozone is found
naturally in small concentrations in the stratosphere, a layer of
Earth's upper atmosphere.
In this upper
atmosphere, ozone is made when ultraviolet light from the sun splits an
oxygen molecule (O2), forming two
single oxygen atoms.
If a freed atom
collides with an oxogen molecule, it becomes ozone.
Stratospheric
ozone has been
called "good" ozone because it protects the Earth's surface from
dangerous ultraviolet light.
Ozone can also
be found in the troposphere, the lowest layer
of the atmosphere.
Tropospheric
ozone (often termed
"bad" ozone) is man-made, a result of air pollution from internal
combustion engines and power plants.
Automobile
exhaust and industrial emissions release a family of nitrogen
oxide gases (NOx) and volatile organic compounds (VOC),
by-products of burning gasoline and coal.
NOx and VOC
combine chemically with oxygen to form ozone during sunny, high-temperature
conditions of late spring, summer and early fall.
High levels of
ozone are usually formed in the heat of the afternoon and early evening,
dissipating during the cooler nights.
Although ozone
pollution is formed mainly in urban and suburban areas, it ends up in rural
areas as well, carried by prevailing winds or resulting from cars and trucks
that travel into rural areas.
Significant
levels of ozone pollution can be detected in rural areas as far as 250 miles
(402 kilometers) downwind from urban industrial zones.
Avoiding
and Reducing Ozone
When you inhale ozone, it travels throughout your
respiratory tract.
Because
ozone is very corrosive, it damages the bronchioles and alveoli in your lungs,
air sacs that are important for gas exchange.
Repeated
exposure to ozone can inflame lung tissues and cause respiratory infections.
Ozone
exposure can aggravate existing respiratory conditions such as asthma, reduce
your lung function and capacity for exercise and cause chest pains and
coughing.
Young
children, adults who are active outdoors and people with respiratory diseases
are most susceptible to the high levels of ozone encountered during the summer.
In
addition to effects on humans, the corrosive nature of ozone can damage plants
and trees. High levels of ozone can destroy agricultural crops and forest
vegetation.
Avoiding Ozone Exposure
To protect yourself from ozone exposure, you should be aware of the Air Quality Index (AQI) in your area everyday -- you can usually find it in the newspaper or on a morning weather forecast on TV or radio.
To protect yourself from ozone exposure, you should be aware of the Air Quality Index (AQI) in your area everyday -- you can usually find it in the newspaper or on a morning weather forecast on TV or radio.
You
should also be familiar with the U.S. Environmental Protection Agency (EPA)
guide for ozone-alert values.
What
do the numbers in the AQI mean? The AQI measures concentrations of five air
pollutants: ozone, sulfur dioxide, particulate matter, carbon monoxide and
nitrogen dioxide.
The
EPA has chosen these pollutants as criteria pollutants, but these are not all of
the pollutants in the air. These concentrations are compared to a standard set
out in federal law.
An
index value of 100 means that all of the criteria pollutants are at the maximum
level that is considered safe for the majority of the population -- a yellow
alert on the chart below.
Numbers
above 100 indicate higher concentrations and therefore a greater risk to most
individuals.
To
reduce your exposure to ozone, you should avoid exercising during afternoon and
early evening hours in the summer.
Make Your Own
Ozone Detector
You can make ozone test strips to
detect and monitor ozone levels in your own backyard or around your school. You
will need:
·
corn starch
·
filter paper (coffee filters work well)
·
potassium iodide (can be ordered from a science education
supplier such as Carolina Biological
Supply or Fisher Scientific)
Basically,
you make a paste from water, corn starch and potassium-iodide, and you paint
this paste on strips of filter paper.
You
then expose the strips to the air for eight hours.
Ozone
in the air will react with the potassium iodide to change the color of the
strip.
You
can then read the ozone concentration from a chart that is available at this Web site.
You
will also need to know the relative humidity,
which you can get from a newspaper, weather broadcast or home weather station.
Reducing Ozone Pollution
There are several ways you can help to decrease ozone pollution:
There are several ways you can help to decrease ozone pollution:
· Limit using your automobile during afternoon and early
evening hours in the late spring, summer and early fall.
· Do not use gasoline-powered lawn equipment during
these times.
· Do not fuel your car during these times.
· Do not light fires or outdoor grills during these times.
· Keep the engine of your car or boat tuned.
· Make sure that your tires are properly inflated.
· Use environmentally safe paints, cleaning and office
products (some of these chemicals are sources of VOC).
· Conserve energy.
Besides
personal attempts to reduce ozone pollution, the EPA has initiated more
stringent air-quality standards (such as the Clean Air Act and its
modifications) to reduce air pollution.
Compliance
with these standards by industries, manufacturers and state and local
governments has significantly reduced the levels of many common air pollutants.
Ozone
concentration in the troposphere has also decreased in the past 10 years.
With continued
conservation and reduction practices, adherence to ozone-pollution warnings,
research and government regulation, ozone-pollution levels should continue to
fall.
Perhaps future
generations will not be threatened by this environmental pollutant.
.
Air Quality Index | Color | Air Quality | Prediction |
0 to 50 | Green | Good | No health impacts are expected. |
51 to 100 | Yellow | Moderate | Unusually sensitive people should limit prolonged outdoor activity. |
101 to 150 | Orange | Unhealthy for sensitive groups | Active people and those with respiratory disease should limit prolonged outdoor activity. |
151 to 200 | Red | Unhealthy | Active people and those with respiratory disease should avoid prolonged outdoor activity; all others should limit prolonged outdoor activity. |
201 to 300 | Purple | Very unhealthy | Active people and those with respiratory disease should avoid all outdoor activity; all others should limit outdoor activity. |
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