Air Quality

"Remember when atmospheric contaminants were romantically called stardust?" (5).

When Lane Olinghouse uttered this statement, he was refering to the worsening problem of air pollution. The air quality of various areas, especially cities like Houston, has dramatically decreased, mostly due to industrialization and the use of automobiles. With that decrease came an increase in health risks and government spending to reduce pollution. In order to determine how to solve this problem, there must be ways to test and treat the air in the city. But more importantly, the causes of air pollution have to be determined, so that people can take action to help reduce and solve this problem

The most effective way of determining the quality of an area's air is by determining the acidity of its rain. The air quality and acidity of rain in a region are directly proportional. Acidity of rain, when measured properly, can usually determine an area's risk of contaminated air. There have been many stories of "acid rain" contaminating an area's lakes or corroding statues. But what exactly is acid rain? Simply, it's overly acidic precipitation, or rain that is harmfully acidic. (4) Normal rainwater is slightly acidic and has a pH of around 5.6. Caused by carbon dioxide from the air dissolved by rain water, slightly acidic normal rain is useful in dissolving minerals so they can be absorbed by plants. Rain only becomes harmfully acidic, or acid rain, when there is too much CO2 or other chemicals in the air. (4) These chemicals are the stem of all air pollution.

Sulfur dioxide, SO2, and nitrogen oxides, NO, make up most of the acids in acid rain. They are released in the burning of fossil fuels such as coal or petroleum, which give off smoke. This smoke is released into the surrounding air and bonds with the water molecules around it, forming acid rain. Half of the SO2 and NO in the atmosphere are also natural. They can be released from volcanoes, swamps, lightning, or rotting organic materials. (4) But it is the other half, the manmade pollutants, that cause the most damage. When we burn fossil fuels, we release the gasses into our atmosphere, causing the normally harmless amounts of SO2 and NO to double and become hazardous to the environment. Yearly, mankind adds about 100 million metric tons of SO2 and 35 million tons of NO to the atmosphere. (4) These substances alone are enough to cause serious problems, but the burning of hydrocarbons creates the largest and most harmful pollutant: ozone. Hydrocarbons are unburned or partially burned gasoline vapors that are toxic when released into the air. When they react with the NO's already in the air, they form ground level ozone. (1) Although ozone in the upper atmosphere, or stratosphere, is beneficial by blocking the sun's harmful rays, it is destructive in the lower atmosphere. Ozone can have lasting health effects, but most people are only affected by it during day-long exposure. During the day, ozone levels become ten times higher than normal in urban areas, causing problems for people who spent a lot of time outside daily. (5) Although ozone is generally caused from large emissions of hydrocarbons and nitrogen oxides, such as from industries, normal people are responsible for large amounts of ozone also. In Baltimore, motorboats and lawnmowers alone contribute more ozone than all of industry put together. (3)

In Houston, a similar problem exists due to the frequent use of automobiles. The Environmental Protection Agency, or EPA, sets ozone laws with a margin of safety just below the "threshold at which people begin to suffer adverse effects." (3) Ozone levels are rated from good to dangerous, with anything below moderate being harmful. But despite these laws most large metropolitan areas, including Houston, fall short of federal ozone standards. It is estimated that 60% of Americans live in an area that fails to meet one or more federal air quality standards. (2) Houston usually falls into the "good" category, although in 1993 we had twenty-two "moderate" days. Just the other day there were ozone warnings at the end of the ten o'clock news. Yet reducing ozone in Houston will remain a difficult problem because of Houstonians' dependence on automobiles, the leading producers of hydrocarbons. (7) This ozone that is produced in Houston also affects its surrounding areas. Wind can carry ozone from one city to another, and even from one state to another. Most of the SO2 and NO produced from industries is carried up to 620 miles from its source. (4) Yet probably the most harmful aspect of ozone is that it is the most frequently occurring substance in smog. (6)

Smog is a haze made up of thousands of different pollutants, the most common being ozone. It is otherwise known as "dirty fog" and its name is taken from smoke fog. Aerosols also make up large portions of smog. Yet smog is a problem especially in Houston because smog needs high temperatures to develop. When temperatures are in the mid-eighties F or higher and there is little wind, the present ozone and other pollutants will mix with natural fog already in the air to form smog. Although Houston doesn't have as significant a smog problem as Los Angeles or Mexico City, it is still considered to be unsafe to be outside during high potential smog days. (5) In general, the hotter the temperature is outside, the higher the chances of smog forming if there are enough pollutants. (1)

The direct consequences of exposure to smog are unknown, although air pollution has been found to be very hazardous to human health. When people breath unclean air, pollutants come into direct contact with their lungs. Polluted air can burn eyes, irritate throats, and affect breathing. Some chemicals can cause adverse health effects if released in large quantities over long periods of time. (7) One study has shown that it takes childrens' lungs as much time to recover from breathing polluted air as they have been breathing the air. Researchers at the University of California estimate that the use of gasoline and diesel fuel in the United States alone may cause up to 30,000 deaths every year. (1) Air pollution has been known to cause cancer, birth defects, brain damage, and damage to the nervous and respiratory systems. This is compounded by the fact that the average adult breathes about ten cubic meters of air per day. (7)

In Texas, there are four metropolitan areas which continuously exceed national standards for ozone levels: Houston, Dallas/Ft. Worth, El Paso, and Beamont/Port Arthur. Of those Houston has the unsafest levels of ozone and contaminate air. The causes of this pollution are spread citywide. Houston releases 1,370 tons of nitrogen oxides per day. 74% are from industrial, and 26% are from cars. Houston also emits 4,045 tons of carbon monoxide per day, of which 68% is industrial. The other 32% also comes from cars. In 1990, Houston vehicles traveled a total of about 38 million miles. (7) Add to that the gasoline burned each mile and Houston's pollution problem is evident. Yet most air pollution is still industrial. Large industries produce 41% of harmful emissions in the city, while small industries produce 20%. Of those industries, chemical industries release the most toxins into the air, followed closely by petroleum refining industries. Houston Lighting & Power gave off 99,215.6 tons of pollutants in 1993. Industries that burn coal release SO2, NO and CO2. Petroleum and gas burning releases CO2, and natural gas burning releases NO and CO2. All together, Harris County released 42,526,385 pounds of toxins into the air in 1993. (7)

The best way to measure the air quality in Houston is by measuring the acidity of the rain. One way of doing this is called titration. Titration is a test in which the acid is neutralized with a known base with an indicator present. The indicator then reveals the strength of the acid. (4) The average pH of Houston is 5.07 and the lowest it has recently been is 4.62. (7) In order to observe the effects of air pollution, the best places to measure the acidity of rain would be in industrialized and non-industrialized areas.


1. Bernards, Neal. The Environmental Crisis. San Diego: Greenhaven Press, Inc., 1991.

2. Buchdahl, Joe. "Health Effects of Urban Air Pollution." Air Quality Information Resources. 15 Feb. 1996.

3. Krupnick, Adam J. and J.W. Anderson. "Revising the Ozone Standard." Online. 17 October 1999. Available WWW: .

4. McCormic, John. Acid Rain. New York: Gloucester Press, 1986.

5. Miller, Christina G. And Louise A. Berry. Air Alert. New York: Antheneum Books, 1996.

6. "Spare The Air Homepage." Online. 17 October 1999. Available WWW: .

7. Texas Environmental Almanac. Austin: Texas Center For Policy Studies, 1995.

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