1. What is ozone and how is it formed?

Ozone is a form of oxygen that consists of three chemically bonded oxygen atoms (O₃) instead of the normal atmospheric oxygen, which consists of two oxygen atoms (O₂). Ozone is formed by the reaction of an oxygen atom with an oxygen molecule. Oxygen molecules are formed by electrical discharges and/or certain types of radiation such as ultraviolet light in the air.

2. What is the difference between good ozone and bad ozone?

The difference between good ozone and bad ozone depends on which layer of the earth's atmosphere the ozone is found. Good ozone, or stratospheric ozone, is found in the stratospheric layer of the atmosphere. The stratospheric layer reaches from ten to thirty-one miles above the earth's surface. Within this layer, good ozone is made and destroyed naturally all of the time. The layer of stratospheric ozone varies in thickness for this very reason. Stratospheric ozone acts as a filter and absorbs the sun's ultraviolet rays, therefore, warming the atmosphere and filtering out harmful ultraviolet radiation from reaching the earth.

Bad ozone, or ground-level ozone, is found in the tropospheric layer, which is about 10 miles thick, from the ground up (also known as ambient air). Ground-level ozone is composed of natural atmospheric gases, volatile organic compounds (VOCs), nitrogen oxides, and sunlight. Ground-level ozone levels are usually higher on hot, sunny days. Cars produce most of the nitrogen oxides and VOCs, so times of increased vehicle use also increases the amount of ozone in the troposphere. Ground-level ozone is one of the "criteria pollutants," those that are most prevalent in the ambient air.

3. What are CFCs and why are they harmful?

Chlorofluorcarbons (CFCs) are the main culprits in the destruction of the stratospheric ozone layer. CFCs were first introduced in the 1920s as refrigerants and coolants, propellants for aerosol sprays, and cleaning solvents. CFCs are not easily degradable, so they rise up into the stratosphere where they are broken down by ultraviolet light. The chlorine atoms then destroy the ozone in a series of complex chemical reactions. One chlorine atom has the potential to destroy as many as 10,000 ozone molecules before it bonds with another atom and returns to the troposphere.

4. Why is ozone considered a secondary pollutant?

Ozone is considered a secondary pollutant because, in order for it to form a chemical reaction between "precursor" pollutants must occur. Common precursor pollutants to ground-level ozone include VOCs, nitrogen oxides, and energy (sunlight).

5. What are some problems caused by ground-level ozone?

Ozone molecules are highly reactive; therefore, they have an oxidizing effect on practically everything they come in contact with. They can damage lung tissue, crops, plastics, rubber, paints, etc. In humans, health symptoms include: dry mucous membranes in the mouth, nose, and throat; headaches; vision changes; lung congestion; and edema. Due to their lacking immune systems and/or health complications, the most susceptible to ozone dangers are the elderly, the sick, and babies.

6. What are the current ground-level ozone standards in the United States?

In 1997, the U.S. Environmental Protection Agency revised its National Ambient Air Quality Standard for ground-level ozone. The new standard is 0.08 parts per million measured over eight hours. This replaced the old standard of 0.12 parts per million measured over one hour. Also, the average of the fourth highest concentration over a three-year period will determine whether an area is out of compliance.

7. What can be done to reduce the amount of ground-level ozone in the troposphere?

During the summer months, the level of ozone in the atmosphere is much greater than in the winter time. In order to reduce the degree of ground-level ozone, people need to follow this list of guidelines:

• Limit daytime driving ¾ combine errands.
• Ride the bus or car pool to work.
• Walk or bicycle for short trips.
• Avoid prolonged idling or jack rabbit starts.
• Refuel carefully (preferably at night) ¾ don't top off your tank.
• Postpone mowing lawns until evening.
• Use latex rather than oil based paints.
• Save energy ¾ don't overcool houses or offices.
• Wash dishes or clothes with full loads.
• Reduce industrial VOC and NOx emissions.

8. What can be done to reduce the degradation of stratospheric ozone?

In order to reduce the effect of ozone depletion in the stratosphere, the general public and industry must follow these guidelines:

• Promptly repair leaks in your refrigerator or air conditioner.
• Make sure the CFCs are recycled when these units are serviced.
• If you scrap your car, make sure that the CFCs in its air conditioning are recycled.
• Use alternatives to home air conditioning.
• Purchase halon-free fire extinguishers.
• Support laws requiring CFC recycling.

9. What are some commercial uses for ozone?

Most people may not know that there are numerous commercial uses of ozone under controlled conditions. Since ozone is a very reactive molecule, it bonds to bacteria and odors, actually purifying the substance; whether it be food, water, or solid materials. Ozone is used in industry for:

• Preservation & storage of fruits and vegetables.
• Disinfection (germicidal effects).
• Retardation of metabolism in fruits, making them last longer.
• Preservation of meats, cheeses, & eggs.
• Filtration & preservation of beverages.
• Disinfection & removal of odors.
• Disinfection of swimming pools.