All About The Ozone

Last Updated on June 7, 2020 by admin

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.


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.


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.


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.


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.


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.


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.


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.


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.


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.



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.


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.



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).


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.



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.


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.



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.


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