Source: National Oceanic and Atmospheric Administration Global Surface Temperature Anomalies, National Climatic Data Center, Asheville, NC January 10, 2000.

Why do we care about air pollution?

Put simply, because it's nasty stuff. Air pollution causes short- and long-term damage to both human health and the health of our ecosystem. While some pollutants are localized and affect only one geographic area, air pollution is global in its scope. Air pollution does not respect geographical boundaries such as city limits, state lines, and national borders. Rather, what we do in our homes and neighborhoods affects not only our own communities but also communities as far away as South America and Asia. It's really just nasty, nasty stuff.

World Climate Changes

For many years we have been inundated with statistics, research, and information on the ill effects of global warming and greenhouse gases. Scientists agree that world sea and land temperatures have increased over the past century, ("Throw away those bulky winter coats and space heaters, Jeremiah, it's 1º warmer!" ) but they often disagree on the specific causes. Whatever the cause, however, it is clear that these global warming trends threaten human health and the lives and habitats of different plant and animal species. Current scientific evidence shows that warmer oceans mean a decrease in oceanic plant and animal life, and that warmer air temperatures could expand the habitat of various infectious diseases, influence where we are able to live, and impact on where food can be grown. In order to be prepared for these potential effects, we need to know how much the planet is warming, how long it has been warming, and the cause of these warming trends. The answers to these questions will provide us with a basis for making long-term policy decisions about such issues as pollution control, water resource management, and agricultural planning. And no, you can not throw away your space heater yet!

Source: "What is Global Warming" National Geophysical Data Center, NOAA.

Global warming is believed to be a result of human pollutants that increase the "greenhouse effect", a term that reflects the similarity between the heating of the earth and the workings of a greenhouse. In a greenhouse, solar radiation penetrates the glass covering, but much of the outgoing infrared radiation does not penetrate the glass; it is absorbed and turned into heat. Thus, warmth is trapped beneath the glass dome. As a result, the interior of the greenhouse is warmer than the outdoor temperature. The earth's surface is heated in a similar manner. Our clear atmosphere acts as the glass dome. As the sun's rays pass through the atmosphere, the earth's surface is warmed. The surface emits some infrared radiation back into the atmosphere. Natural "greenhouse gases", such as water vapor, carbon dioxide, and other gases, trap the infrared radiation, creating heat, and warming the lower atmosphere. Under ordinary natural environmental conditions, the greenhouse effect maintains the earth's average temperature at roughly 60°F. Without this natural warming process, the earth's average temperatures would be closer to 0°F.1 While the greenhouse effect is necessary for ecosystem survival, too much global warming over a long period of time is detrimental to life on earth.

Source: "Global Warming, Climate" U.S. Environmental Protection Agency

As early as 1896, a Swedish chemist named Syante Arrhenius predicted a link between rising atmospheric CO2 and potential climatic temperature increases. More recent studies have proved that since the Industrial Revolution, humans are accountable for higher distributions of many greenhouse gases that absorb heat including chlorofluorocarbons (CFCs), carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4), and ground-level ozone (O3). Scientists generally agree that the burning of fossil fuels to run automobiles, heat buildings, and power factories has increased levels of various gases. When compared to pre-industrial times, CO2 emissions have increased 30%, methane levels more than doubled, and N2O levels have risen about 15%.2 The increase in these gases has caused the earth's atmosphere to trap and absorb more heat than in previous times.

Ozone Depletion

You may have heard people talking about the relationship between air pollution and ozone (O3) in our atmosphere. The most common claim is that man-made pollutants are destroying the ozone layer. Well, there are two basic reasons for this claim: 1) Man-made pollutants are destroying the ozone layer, and 2) Man-made pollutants in fact are destroying the ozone layer. Really. No fooling.

Five atmospheric layers surround the earth: the troposphere, the stratosphere, the mesosphere, the thermosphere, and the exosphere. Ozone exists in the two layers closest to the earth's surface. Chemicals released into our air either deplete ozone in the stratosphere, where we need it, or create ozone in the troposphere, where it is detrimental to human health.

Source: NOAA Aeronomy Laboratory, 2000

The troposphere is the layer closest to the earth's surface. The weather we experience all occurs within this layer. In the troposphere, ground-level (or "bad") ozone is created when NOX and VOCs are released into the air and exposed to sunlight. This ozone is considered an air pollutant, and it plays an important role in the formation of smog. It is bad for human health and causes a variety of cardiovascular and respiratory problems, as well as reducing our visibility on smoggy days. This ozone also acts as a greenhouse gas contributing to global warming. Human activity, particularly automobile use and industrial processing, has contributed to increased ground-level ozone.

The upper-atmospheric (or "good") ozone layer lies roughly 6-30 miles above the earth's surface in the stratosphere. This ozone occurs naturally and is essential to human life, for it acts as a protective shield blocking harmful UVB rays from the earth's surface. Think of it as an enormous pair of sunglasses-just a tad smaller than the ones that the eye doctor gives you after dilating your eyes. Ultraviolet radiation is considered harmful to human, animal, and plant life because it can enter cells and destroy the deoxyribonucleic acid (DNA) in our systems. Laboratory and epidemiological studies link the increase in UVB exposure to cataracts, impaired immune systems, and skin cancers.

Three main sources contribute to upper-atmospheric ozone depletion: human activity, natural sources, and volcanic eruptions. It is estimated that human activity is responsible for roughly 75-85% of the ozone damage.3 Chemicals including chlorofluorocarbons (CFCs), halons, and other ozone depleting substances like those used in coolants, fire extinguishers, and solvents all contribute to ozone erosion. In September 2000, the ozone hole was the largest on record.4 See, man-made pollutants are destroying the ozone layer. Or so we hear.

Acid Rain

Air pollution is a major factor in the formation of acid rain. Pollutants that contribute to acid rain mainly come from the burning of fossil fuels. When SO2 and NOX are released into the atmosphere they react with oxygen and water to produce harmful acidic compounds often referred to as acidic deposition or acid rain. Acidic compositions fall to the earth's surface in both dry and wet form; thus the term "acid rain" is a bit misleading. Roughly 10-50% of these particles are scattered on buildings, cars, plants, and other objects in a dry form. The remaining deposition occurs when acidic particles mix with rain, snow, or fog and fall to the earth's surface. But let's not quibble over semantics. Both dry and wet deposition of acids are equally harmful to the ecosystem and human structures.

Acid rain attacks sensitive water bodies, specifically those that are surrounded by soils that lack the "buffering capacity" to neutralize the acidic compounds. Many regions in the US have sensitive soils, including the Adirondacks, the mid-Appalachian highlands, the upper Midwest, and the high elevations in the West.5 In these areas, forests and water bodies have been degraded and destroyed.

Acidic concentrations in water are measured by pH levels. The pH scale ranges from 0 to 14, with 7 being the neutral point. Values of pH above 7 represent alkaline or basic soils or liquids; measurements less than 7 indicate an excess of hydrogen ions, meaning the sample is acidic.6 Pure rainwater generally has a pH of 5.6. Ecosystems do not appear to be disturbed by this level of acidity. When pH levels drop below 5, most aquatic life begins to falter. The reproductive rate of fish is one of the first indicators of high acidity in water. Newly hatched fish often will not survive in regions with pH levels lower than 5, and if they do survive they are often deformed. Similar effects have been seen in insects, frogs, salamanders, clams, and crayfish.7 Since the 1950s, a number of regions around the world have shown higher acidic levels in their waterways. In the 1970s, 50% of the lakes above 2000 feet in the Adirondack Mountains of New York were found to have pH levels below 5.8 Fish do not like acid rain.

Smoky Mountain National Park on clear and hazy days. Source: The National Park Service Visibility Monitoring Program

Acid rain also contributes to tree damage, particularly at high elevations. Clouds with high acidic concentrations tend to linger at higher elevations, causing leaf damage. Consequently, trees become more susceptible to injury and disease. Soils with high acid compounds also strip away vital soil nutrients critical for plant growth. Plants do not like acid rain. Our surroundings are being visually degraded by acid rain. In the eastern U.S., sulfate particles account for more than 50% of visibility problems.9 Our national parks are affected by reduced visibility, as visitors are unable to see across mountain ranges and valleys on high-pollution days. People do not like acid rain.

Acidic particles also contribute to the corrosion and discoloration of metals, stone, and paint. Over time, these particles have damaged national monuments and historic buildings, causing aesthetic as well as economic damage. Large sums of money are spent annually to clean and repair objects that are being attacked by acid rain. Buildings and monuments do not like acid rain.

In 1990, the Acid Rain Program was implemented under the Clean Air Act. The legislation seeks to reduce both SO2 and NOX. The program mandates that by 2010, annual SO2 emissions must decrease by 10 million tons from 1980 levels. NOX must be reduced by 2 million tons from 1980 levels by the year 2000. Since the implementation of EPA's acid rain program, there have been dramatic reductions (10 - 25%) in sulfates deposited in many of the most acid-sensitive ecosystems located in the northeastern United States.10 You see, nobody likes acid rain, not even politicians.

1. "About Global Warming." The Environment Site. http://environmentsite.com/global.htm (1 Dec. 2000).
2. Clean Air Council. "Global Warming." http://www.cleanair.org/globalwarming/science.html (20 Nov. 2000).
3. Busman, Joelle, and Cary Belen. "The Ozone Layer: important components of ozone education." http://www.umich.edu/~gs265/society/ozone.htm (22 Nov. 2000).
4. "Ozone hole larger but improvements to come", United Press International, October 15, 2000.
5. "Environmental Effects of Acid Rain." United States Environmental Protection Agency, April 1999. http://www.emp.gov/acidrain/effects/envben.html. (30 Oct. 2000).
6. Ristinen, Robert A., and Jack Kraushaar. Energy and the Environment, New York: John Wiley & Sons, Inc.. 1999. p. 315.
7. Ibid. p. 317.
8. Ibid. p.. 317.
9. "Environmental Effects of Acid Rain." United States Environmental Protection Agency.
10. "Latest Findings on National Air Quality." United States Environmental Protection Agency, Office of Air Quality Planning and Standards, August 2000. http://www.epa.gov/aritrends/ (15 Oct. 2000).