Ozone Virtual Briefing Document

What is Ozone?

Ozone is a gas that occurs both naturally and as a result of man-made
pollution. Ground-level ozone, commonly known as urban smog, is a product
of complex chemical reactions in the air. It is a product of: (1) volatile organic
compounds (VOCs), hydrocarbons emitted from sources such as
automobiles, chemical plants, bakeries, dry cleaners and other industrial
facilities; evaporating gasoline, paints and solvents; and (2) nitrogen oxides
(NOx), emitted from sources such as automobiles, electric generating plants,
lawn mowers, trees and other natural sources. Ground-level ozone is not
emitted from any specific source as are most other air pollutants.

What Should I Know About Ground-Level Ozone?

When most people think of ozone, they think of the ozone that occurs high up
in the atmosphere, protecting us from the damaging rays of the sun, which
can cause skin cancer. But there is another type of ozone that occurs near the
ground, often in urban areas. This ground-level variety of ozone is the main
component of smog and too much of this ozone can be harmful to your health.

Where does ground-level ozone, or smog, come from?
Some ground-level ozone occurs naturally. It is not emitted directly, but is
formed when sunlight reacts with hydrocarbons and nitrogen oxides during
warmer months. Hydrocarbons come from natural and man-made sources,
such as trees, soil, auto emissions, other combustion processes, and from
evaporating gasoline, solvents and paints. Nitrogen oxides come from auto
emissions, power plants and all fossil fuel combustion, from lawn mowers to
tractors. Most urban smog is produced during the summer months.

Why is too much ground-level ozone bad?

High concentrations of ground-level ozone can damage plants and cause
breathing difficulties. According to the EPA, healthy people, as well as those
with respiratory problems, experience breathing problems when exposed to
too much ozone. Ozone can cause temporary diminished lung function, chest
tightness and nausea. At particular risk are children, the elderly and people
who exercise strenuously during periods of high ozone levels. Although health
risks are the most important, high levels of smog can also harm crops and
trees and cause plastics and paints to crack and fade.

When is ozone a problem?

The chemical reactions that form ozone from NOx and VOCs are most active
on hot, sunny days. Thus, for most areas of the country, high ozone levels are
a concern only during the late spring and summer.

Why are excessive levels of ozone a problem?

In high enough concentrations, ozone is highly corrosive and irritating to plant
and animal tissue. It can cause fading and cracking in plastics and paints,
thereby increasing the costs of maintenance for businesses and
homeowners. High levels can damage crops, trees and other plants. In
humans, high ozone exposure can cause respiratory distress, and in extreme
cases, may cause permanent damage to lung tissue.

What is being accomplished to reduce this type of ozone?

Ground level ozone only occurs when emissions from combustion of fossil
fuels react with very hot, sunny, summer days and little or no wind. Smog has
been reduced by half between 1975 and 1994 due to emission controls
resulting from the enactment of clean air legislation. Emission controls have
been installed on industrial plants, solvents have been reformulated to reduce
emissions, and reformulated gasoline is used in nine urban areas with
serious smog problems. Smog will probably never be eliminated completely
as long as individuals use gasoline-powered vehicles, and trees continue to
emit hydrocarbons.

What can individuals do to reduce smog?

  • Use electric lawn mowers rather than gasoline-powered equipment
  • Use electric charcoal starters or "charcoal chimneys" instead of
    charcoal lighter fluid
  • Use paint brushes and rollers, and water based (latex) paints rather
    than spray applicators and oil-based paints and coatings
  • Limit the use of fume producing household products
  • Keep you car's filters and fluids clean, and your engine tuned, to
    increase gas mileage and reduce pollution
  • Use high efficiency motor oil in your car
  • Make sure car tires are properly inflated
  • During the summer, refuel in the evening to reduce evaporative
    emissions
  • Don't top off your car's gas tank
  • Turn your car's engine off when stopped
  • Combine errands for shorter car trips
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