Ozone - the Pollution Paradox
Where Makes the Difference
Ozone...too much is harmful. But so is too little. It's a seeming paradox, but not a real one. When it comes to ozone the where makes the difference. Near the ground, ozone is an air pollutant from man-made emissions. Ten to 30 miles overhead, ozone forms a protective layer that filters dangerous ultraviolet radiation from sunlight.
Unlike its more common cousin, oxygen (O2), ozone (O3) is a highly reactive gas of three oxygen atoms that occurs naturally in only small amounts in our atmosphere.
The earth's atmosphere is a vast chemical factory that continuously forms and destroys substances, including ozone. When everything is working properly, a natural balance maintains a stratospheric ozone layer as a protective sun blocker and dissipates concentrations of ground-level ozone that can harm human health and the living environment.
However, the energy use of an expanding world population has begun to distort this all important ozone balance. Stratospheric ozone is being depleted, while ground-level ozone sometimes builds up to unhealthy levels near and downwind of major urban areas. And, there is no way to move excess ground-level ozone to the upper atmosphere where it could be useful.
Upstairs, Ozone Depletion
Recent measurements show that the amount of ozone in the stratosphere has decreased by about two percent since 1967. What is called the "ozone hole" over Antarctica actually is an area where concentrations are significantly lower than in the rest of the stratosphere. It is estimated that up to eight percent of the protective ozone layer over the United States, Canada and Europe has disappeared. Researchers report that the seasonal "hole" over Antarctica and some populated regions of the Southern Hemisphere thins the ozone layer at times by as much as 60 or 70 percent.
Scientists estimate that every one percent decrease in the ozone layer increases ultraviolet light intensity at the earth's surface by two percent. Known effects of ultraviolet exposure include greater incidence of skin cancer and eye cataracts among humans and diminished crop yields for foods such as peas, beans, squash and soybeans. Phytoplankton, the tiny one celled ocean plants that are a food staple for squid, fish, seals, penguins and whales also are vulnerable.
Stratospheric ozone filters out dangerous ultraviolet radiation by means of a continuous cycle in which oxygen and ozone break down and reform, absorbing ultraviolet light and releasing less damaging kinds of energy. Without enough ozone, the effectiveness of the filter decreases and more ultraviolet radiation reaches the earth. The culprits destroying the stratospheric ozone are chemicals known as chlorofluorocarbons (CFCs) and halons, which are produced and released into the atmosphere by human activity. These substances are very stable and remain unchanged in the air for as long as a century. Other threats to the upper ozone come from chemicals found in certain degreasers, adhesives, dyes, pesticides and fungicides.
During their long lifetime, the CFCs and halons drift up to the stratosphere where they are exposed to high-intensity ultraviolet radiation and break apart. CFCs release highly reactive atoms of chlorine; halons release bromine atoms. The chlorine and bromine atoms are voracious in breaking up ozone and tying up oxygen atoms that might form new ozone. Scientists estimate that a single chlorine atom can destroy up to 100,000 ozone molecules before the chlorine is finally captured by a reaction with hydrogen. One bromine atom can destroy nearly 10 times as much ozone as a chlorine atom.
Even if production of CFCs and halons ceased tomorrow, the full destructive effect on the ozone shield would still be felt years into the future. Even now, releases over the past several decades of the long-lived chemicals are making their way up toward the stratosphere. Worldwide CFC and halon production peaked in 1974 at nearly a million tons per year, declined slightly during the later 1970s, then by the late 1980s had again increased to near the million ton mark. Beginning in 1987, scores of nations, including the United States, entered into international agreements to reduce the production of ozone-depleting chemicals. Without these changes--and a substantial reduction in greenhouse gas emissions--scientists project that stratospheric ozone could be depleted by between five and nine percent during the next century, with an accompanying increase in ultraviolet exposure at the earth's surface of 10 to 18 percent.
Downstairs, Ozone Excess
While the stratospheric ozone layer is being depleted, the atmosphere near ground level has the opposite problem--ozone buildup near major population centers, and the transport of that ozone to other areas.
Near the earth's surface, small amounts of ozone are continuously created and destroyed in ongoing natural cycles. When nitrogen oxides (pollutants formed from the burning of fossil fuels) are added to the air, more ozone is created but then is quickly destroyed again.
The balance of ozone creation and destruction shifts drastically, however, when hydrocarbons are added to the atmospheric mix. Hydrocarbons--vapors from solvents, gasoline, dry cleaning fluids and hundreds of other common substances--actually add to the creation phase of the ozone cycle, while circumventing the destruction phase. Summer heat and the increase in sunlight intensity speed the rate of these chemical reactions, triggering rapid formation of ozone. This is why ozone "health advisories" often are issued during the summer, but never during the winter.
Ozone can have an adverse effect on the human body. High ozone concentrations irritate nasal, throat and bronchial tissues. Ozone attacks certain components of the body's defense system, raising concerns about the effects of ozone exposure on the human immune system. High concentrations of ozone can also harm forests, thereby altering wildlife habitats, lowering crop yields and damaging materials such as rubber, plastics, synthetic fibers, dyes and paints.
While ozone formation occurs most commonly over cities with large numbers of industries, power plants and vehicles, ozone pollution is also found in remote locations--deep in the Maine woods, in rural Vermont and on top of New York's Whiteface Mountain. This occurs because hydrocarbons, nitrogen oxides and ozone itself are carried by the wind many hundreds of miles from their city origins, polluting rural areas. In large urban areas, ozone mixes with other pollutants to create the air pollution condition known as smog. Smog reduces visibility and irritates and inflames eye tissues. Unusually hot and dry weather fosters smog production.
Motor vehicles produce both nitrogen oxides and hydrocarbons. The nitrogen oxides are created when fuel is burned and hydrocarbons are emitted when fuels fail to burn completely and when gas tanks are filled. In 2008, there were 255,917,664 vehicles registered nationwide, compared with "just" 215,496,003 vehicles in 1998, and 193,057,376 vehicles in 1990. The number of trucks alone increased by 16 percent between 1998 and 2008, and nearly 25% from 1990 to 1998 . Lawn mowers, chain saws, power boats and snowmobiles are other sources of pollution derived from petroleum sources. Hydrocarbons also evaporate from paint and protective coatings and from some solvents used in printing and industrial processes. Industry and electric power producers belch out millions of tons of emissions each year, including vast amounts of nitrogen oxides. Worldwide consumption of fossil fuels, a major source of nitrogen oxides, increased almost 20% just from 1990 to 2005 and show no signs of slowing down, as countries like China and India continue their rapid industrialization.
Lifestyle Changes Required
Eliminating ground-level ozone pollution and healing the protective stratospheric ozone shield will mean changes in the materials used in consumer products; in fuels that power cars and tools; in engineering designs for cleaner, more efficient fuel combustion; in energy sources that power factories and homes, and in our individual lifestyles.
An ozone-healthy world will require these changes on both a societal and individual level:
- Replacing CFCs and halons with chemicals that do not destroy stratospheric ozone;
- Using solvents and paints that contain fewer pollutants and fuels that burn cleaner;
- Finding substitutes for fossil fuels, including energy sources such as solar, nuclear, hydroelectric and wind power;
- Modifying individual habits by cutting out unnecessary driving and making more use of mass transit systems and car pooling.
New York State has been a leader addressing ozone issues. As early as 1976, two years before federal action, New York State warned aerosol spray can users of the potential danger of CFC discharges to the air. By 1989, New York and other eastern states were curbing CFC production and use and developing more efficient fuels; actions that were later championed by federal agencies. New York State continues to press for controls on air pollution through its active participation in a number of regional and national organizations. To help control ground-level ozone pollution, New York State requires that low volatility gasoline be marketed during the summer months. For the New York City metropolitan area, New York State requires that gasoline vapors be recovered during the refueling of vehicles as well as during the loading of gasoline storage tanks at service stations, and that vehicles be inspected annually to insure that tailpipe emissions meet established standards. New York State has also joined with other states to adopt tougher motor vehicle emissions standards for hydrocarbons, nitrogen oxides and carbon monoxide.
What You Can Do
Most upstairs ozone solutions require international solutions. But you can help by making sure that a trained specialist removes the Freon (which contains CFCs) before discarding refrigerators, air conditioners, and cars with air conditioners. Check with your local recycling or solid waste department for assistance.
There is much more you can do to reduce downstairs ozone, especially when there is an "ozone health advisory."
Curtail the use of oil-based paints, solvents and other products that evaporate easily or give off fumes. Instead of lighter fluid, ignite grills with electricity or chimney type starter fuels. Limit yard chores that use gasoline-powered equipment.
ON THE ROAD: Limit driving, rideshare, carpool, use public transportation, walk or bicycle. Combine errands in one trip. If you must refuel, do it after dusk. Keep your vehicle well-tuned.
FOR RIDESHARING INFORMATION: Contact your local NYS Department of Transportation Office.
FOR INFORMATION: From May-September, call the Ozone Hotline 1-800-535-1345.