All About Ozone
Whenever it occurs, ozone (O ) is a colorless gas, a form of
oxygen. However, an ordinary molecule of oxygen contains two atoms
while a molecule of ozone contains three atoms ( O + O = O3 ). Because
of ozone's composition, it is reactive. That is, it readily combines
with and oxidizes (breaks down) whatever materials it comes in contact
with, including such biological substances as cells and tissues.
Far above the earth, ozone forms naturally as oxygen produced from
living things moves from the troposphere, the layer of air nearest the
earth's surface, to the stratophere.
(Scientists label the layers of the atmosphere according to the way
temperature changes with altitude.) Air in the stratosphere absorbs
solar energy, or heat from the sun, which in turn creates a
photochemical reaction that produces ozone -- a benefit to the
environment since ozone protects people, plants, and animals from
harmful radiation.
DIFFERENT PROBLEMS; COMMON TIES
The dual ozone problems -- pollution or smog in the troposphere
and depletion of the ozone layer in the stratophere -- are very
different. But the problems have common ties in that they both are
related to air pollutants that come from industry, transportation, and
other human activities.
Although ozone depletion in the stratosphere is a relatively
recent problems, air pollution that contributes to a variety of
environmental hazards is not a new concern. Since the time of the
industrial revolution in the 1800's, people in many urban areas of the
world have suffered from "dirty air." As the number of coal - and oil
burning power plants, factories, steel mills, foundries, and other
manufacturing and processing plants increased, smoke, soot, and other
particulates spewed into the air. Exhaust fumes from more and more cars
and trucks added to the pollution problem. Chemical processing plants,
waste disposal facilities, pesticides, and herbicidies have been
responsible for adding more pollutants -- some of them highly toxic --
to the atmosphere.
EFFORTS TO CLEAN UP AIR POLLUTION
A number of major cities around the world have passed laws
requiring controls on sources of air pollutants. In the United States,
cities like Los Angeles and Pittsburgh began air cleanup efforts during
the 1960's. The federal government also passed a Clean Air Act and
amended it in 1970 to set standards for safe amounts of carbon
monoxide, carbon dioxide, nitrogen oxides, ozone, lead, and
particulates such as soot and dust allowed in ambient air
(concentration of air over a particular community). In 1970, Congress
also set up the Environmental Protection Agency (EPA), which is
responsible for enforcing regulations that protect the environment.
An important part of the 1970 Clean Air Act was an order for
states to develop programs for reducing ozone levels to no more than
0.08 parts of ozone per million parts of ambient air (ppm). The law
stated that the ozone level should not be exceeded more than one day a
year. However, states were unable to meet the standards and in 1979 the
EPA raised the level to 0.12 ppm. Health standards set by the Clean Air
Act and its amendments, along with measures enacted by states and
cities, went a long way to help improve air quality. As an example,
Pittsburgh was once blanketed with smoke and smog that cut off
daylight. But emissions from steel mills, foundries, rail yards, and
other sources were brought under control so that Pittsburgh has become
a more inviable city.
EFFECTS OF OZONE POLLUTION
Geography is a major factor in ozone pollution, with mountain
ranges trapping ozone in valley regions. But wind and climate patterns
also affect the production of ozone. Since sunshine is needed to
produce smog, sunny areas like the southeast and southwest United
States may suffer from smog episodes at any time of the year if air
circulation is poor and other conditions favor the production of ozone.
But in most parts of the nation, ozone pollution is a summer problem
because of the increase in sunshine and the warm, stagnant air that
hovers over metropolitan areas.
Yet the primary causes of ozone pollution are the large industrial
complexes and transportation systems that have developed since the mid-1900s. The highest concentration of industry and motor vehicles is in
major cities where there a re many thousands of sources for "precursor
emissions"-hydrocarbons and nitrogen oxides that will create the by-
product ozone.
HEALTH HAZARDS
High levels of ozone pollution can trigger a number of respiratory
problems. But long-term exposure to ozone pollution may pose an even
greater health risk, according to one study conducted for a three-month
period during 1984. A research team from the University of Southern
California's School of Medicine measured lung function of more than a
thousand second and fifth grade students in Los Angeles and compared
the results with tests of children in a less-polluted area of the
country. Researchers found that "long-term exposure to relatively low
levels of air pollution may be far more dangerous to growing children
than occasional exposure to peak pollution levels."
For the testing, children blew into an instrument called a
spirometer. Measurements from the instrument indicate a person's lung
size and the airflow in the large healed air is transported in the
lungs via a complex system of airways that divide and narrow, and then
is sent to the bloodstream via tiny air sacs. Cells in both the
airways and air sacs are sensitive to and can be damaged by ozone.
WHO'S AT RISK?
For most people, the effects of short-term exposure(one to two
hours) to ozone may subside once they are out of the polluted
environment-perhaps in an air conditioned vehicle or building. But
medical experts say there is some possibility that ozone pollution
could create other health problems in the long-term, as the study with
Los Angeles school children seemed to indicate. In addition, some
groups of people face more ozonerelated health risks than others.
Those most in danger from air pollutants, according to the American
Lung Association, are the elderly, infants, pregnant women, and victims
of chronic lung and heart disease.
EFFECTS OF OZONE ON TREES AND PLANTS
One EPA study, the National Crop Loss Assessment Network(NCLAN),
indicated that when ozone concentration during the growing season
exceeds 0.04 ppm to 0.05 ppm, there is a 10 percent or more loss in the
yield of such major cash crops as soybeans, peanuts, corn, and wheat.
The NCLAN study also showed that ozone exposure
can reduce plant yield in tomatos 33 percent, beans 26 percent,
soybeans 20 percent, and snapbeans up to 22 percent. The
potential crop losses alone a re estimated at two billion to three
billion dollars per year.
Along with poor crop yields, forest damage can be traced to air
pollutants, particularly ozone and acid deposition. Popularly known as
acid rain, acidic deposits include dry and wet substances formed from
gaseous sulfur and nitrogen oxides. Acid rain has been blamed for much
tree and plant damage as well as the death of fish and plant life in
lakes in northeastern United States, Canada, and some European
countries.
III. CONTROLLING OZONE PRECURSORS
According to the Clean Air Act, the EPA is charged with enforcing
NAAQS. In the case of the ozone standard, an area exceeds the limit if
the ozone reading is over 0.12 ppm for more than one hour per day. For
tail pipe emissions from passenger cars, the limits are exstandard for
carbon monoxide is 3.4 gpm. In 1988, the standard for nitrogen oxide
was 1.0 gpm and 0.4 gpm for hydrocarbons, but some federal lawmakers
would like to cut those limits by more than one-half.
The law requires than each state submit a plan to control air
pollutants and identify the geographic areas that exceed the health
standards for ozone and carbon monoxide. The EPA must approve each
state's plan or help a state set up a plan that would meet its
approval. Each state must then apply the rules and regulations to
attain the standards and also prevent its industries from polluting the
air of other states.
MAKING A CASE FOR ALCOHOL FUELS
Alternative fuels such as methanol and ethanol are still another
means of controlling VOCs. Although these fuels produce hydrocarbons,
their hydrocarbons appear to be less reactive to photochemical
processes than those of gasoline.
Methanol, known also as wood alcohol, is produced from natural gas
or coal, and ethanol is distilled from corn. Both fuels can be added
to petroleum or used as pure alcohol fuels. As additives, they provide
more oxygen to gasoline fuel, which means that the mixture burns more
cleanly and cuts carbon monoxide and ozone-producing emissions. Pure
alcohol fuels burn even cleaner than blends but create problems in
vehicle engines that have rubber or plastic parts, which can be
destroyed by alcohol. However, it is a relatively simple matter to
produce alcohol-resistant parts for vehicles. Vehicles that
successfully burn alcohol fuels have long been used in many South
American countries.
CONTROVERSY OVER CONTROL MEASURES
One of the difficulties in setting up pollution control measures
is determining whether information provided by computer experts is
accurate enough to use as a basis for regulations. Analysts apply
mathematical formulas to create computer models that simulate polluted
conditions over a given area. The models also suggest strategies for
controlling air pollution. But some researchers doubt the results,
believing there are too many unknowns, particularly in the complex
chemistry of ozone pollution, to set up accurate control programs based
on computer models.
Nevertheless, the EPA has developed two computer modeling programs
that are considered highly reliable for predicting ozone transport.
But because of the amount of time and personnel required to collect and
validate data, and the computer capacity needed, these models are very
costly to use. EPA officials say it costs from $300,000 to $500,000 to
run the Urban Airshed Model, for example. Costs for running an even
more sophisticated Regional Oxidant Model are between $3 million and $5
million. The latter program has been used to effectively estimate the
transport of air pollutants along the Northeast Corridor (from Maine
to Virginia), but high operating costs have prevented widespread use
for other areas of the nation.
IV. ATTACKS ON THE OZONE SHIELD
OZONE DISTRIBUTION
Although ozone makes up less than 1 ppm of all the gases in our
planet's atmosphere, it is essential to the on earth. Scientists
assume that in the early days of the earth's evolution there was no
atmosphere, but gases from planet surfaces and volcanos slowly
collected. At first, the gases were little protection from the sun's
UV radiation. But according to some evolutionary theories, life-forms
on earth may have been able to develop in water that filtered out most
of the UV rays but allowed enough visible light for chemical reactions
to take place.
As organisms began to make use of the plentiful supply for oxygen
on earth, the ozone layer also began to develop and to absorb most of
the sun's UV rays that could harm crops, marine life, and human health.
Both life on earth as we know it and the ozone layer that protects our
planet's life support system depend on the oxygen supply in our
atmosphere.
DISCOVERY OF THE OZONE "HOLE"
Why did scientists become concerned about the ozone layer? A
number of events prompted scientific research into the possibility that
the ozone layer might be in danger. One was a debate that developed
over a fleet of several hundred huge aircraft, called supersonic
transports (SSTs). Congress planned to fund the manufacture of two
U.S. prototype SSTs, modeled after the Concord built in France, and
congressional leaders wanted information on what impact the SSTs would
have on the s tratosphere where the aircraft would be flying.
Scientific studies during the early 1970s showed that SSts flying
through the stratosphere released nitrogen oxides in exhaust gases.
Ironically, nitrogen compounds that help produce ozone in the
troposphere are part of a chemical process that destroys ozone in the
stratosphere. Although the threat to the ozone layer was a
consideration in whether or not SSTs should be manufactured, the
project eventually was dropped because the production of SSTs became
too costly.
V. EFFECTS OF STRATOSPHERIC OZONE LOSS
HUMAN HEALTH PROBLEMS
According to research reports at the June 1986 international
conference and other published reports since that time, a one percent
loss in stratospheric ozone results in a two percent increase in UV
radiation. In turn, the increased radiation could cause a variety of
human health problems, including damage to the immune system, which
would weaken the body's ability to fight diseases, and higher
incidences of such eye discorders as cataracts, retinal damage, and
corneal tumors.
Increased UV radiation also would bring about more cases of skin
problems such as premature aging of the skin and higher incidences of
squamous-cell carcinoma, a type of nonmalignant cancer that affects
mostly light-skinned people.
Currently, more that 500,000 Americans each year develop skin
cancer. With each one percent lose in ozone, the skin cancer rate is
expected to increase by three to six percent. Although the vast
majority of skin cancers can be cured, one type, melanoma, is more
dangerous and affects people of all skin colors. An estimated 6,000
Americans died from the disease in 1988, and the number of cases is
expected to rise. In some instances melanoma has been linked to
blistering sunburns, but the disease is more likely related to genetic
factors, viruses, and exposure to chemical carcinogens (cancer-causing
substances).
ENVIRONMENTAL EFFECTS
Since the 1970s, a number of experiments have been conducted at
research universities to determine how UV radiation affects land-based
plants and marine life. According to a research report presented at
the June 1986 international conference and summarized by the World
Resources Institute (WRI), enhanced UV radiation could slow the process
of photosynthesis, reduce leaf area, and decrease water use efficiency
in many plants. Thus yields of some crops such as soybeans would
decrease, costing billions of dollars in crop losses.
Aquatic life also could be endangered by ozone depletion.
Although some aquatic species such as anchovy larvae have developed a
tolerance for increased UV radiation, greater ozone depletion might
result in abnormal development of larvae or kill of larvae, which are
used worldwide in animal feeds. There is some speculation that
organisms such as blue-green algae that are unharmed by UV light could
dominate aquatic systems.
VI. PHASING OUT CFC'S AND HALONS
CFC SUBSTITUTES
The Montreal agreement called for specific limits on chemical
compounds found to be the most destructive of stratospheric ozone,
including the CFC compounds 11,12,113, and the halons 1211 and 1301.
According to a Science News magazine report, manufactures of CFCs
and halons are using two methods to develop substitute products that
will not be a threat to the ozone layer. One method involves changing
the common molecular structure of CFCs "by sticking a disruptive
hydrogen atom into the stable arrangement of chlorine and fluorine.
Because these new molecules are less stable, they break up in the lower
atmosphere and a re less liable to reach the stratosphere where they
can do harm."
Some CFC compounds that are less harmful to the ozone layer are
already being marketed. The Du Pont company is producing HCFC 22 (or
CFC 22) as a replacement for CFC 12 that has commonly been used in the
manufacture of foam containers for the fast food industry and in
refrigerants, particularly motor vehicle air conditioners.
OTHER WAYS TO REDUCE OZONE-DEPLETING EMISSIONS
While chemical companies work on research and development of new
products that will replace halons and CFCs, some industries are looking
at other means for cutting back on gaseous emissions that have damaging
effects on the ozone layer. One example is a new type of technology
for refrigeration. According to a report in Business Week, research
scientists in the United States and Japan "are developing devices that
rely on hydrogen and nickel-alloy 'sponges.' The units work because
the sponges release and reabsorb hydrogen. When hydrogen is released,
the metal cools off, chilling air that flows over it."
In other efforts, manufacturers are seeking ways to redesign
mobile air conditioners so that there are fewer joints and tighter
seals and valves, which would cut back on CFC emissions. CFCs also
escape from mobile air conditioners during servicing, but if the
coolant is recycled rather than allowed to evaporate, leakage of CFCs
can be prevented. Removing the coolant from refrigerators and air
conditioners before they are scrapped is another way to prevent the
release of CFCs.
VII. WHAT IN THE WORLD CAN WE DO ?
A "GLOBAL COMMONS"
Individuals can begin by learning how human activities in any part
of the world can have a global impact. As EPA director Lee Thomas has
put it: "The depletion of stratospheric ozone and a global warming from
the 'greenhouse effect'... are clear examples of a 'global commons'
environmental problem. All nations a re responsible for contributing
to recent changes in our atmosphere-although the industrially developed
nations must shoulder most of the responsibility. All nations will be
affected by depletion of the ozone layer and by global climate
changes."
People in industrialized nations also are beginning to pay
attention to the many scientific reports issued since the 1970s that
have described the damaging effects of acid rain. Acid deposition is
not yet an environmental problem with the global scale of ozone
depletion and a forced greenhouse effect (although many experts argue
it soon will be), but acid rain spills over state and national
boundaries. In Europe, for example, many nations have realized that
industrial emissions create acid rain problems far from their sources,
so at least twenty countries are coordinating efforts to control acid
rain precursors.
GLOBAL HOUSEKEEPING
Solutions to the acid rain problem are closely related to other
pollution control efforts-reducing urban smog and global warming and
destruction of the ozone layer. In short, atmospheric pollutants have
to be cleaned up before any of the global and regional problems they
cause can be eased or eliminated.
Although the United States has not fully supported efforts to
control acid rain, the nation has often led the way in scientific
research on the environment and could provide leadership in policies
that would guard against environmental crises. Some lawmakers
consistently have called for action even before scientists have
resolved the many uncertainties regarding the causes of ozone depletion
and the enhanced greenhouse effect. An example is U.S. Senator John
H. Chafee of Rhode Island, chair of the Senate Subcommittee on
Environmental Pollution.
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