Environmental Issue Air Pollution and Human Health

Caution: the air you breathe may be hazardous to your health. It may even kill you—especially if you have heart or respiratory problems. Two major human sources of air pollution are motor vehicle exhaust and industrial emissions. The exhaust pipes on our cars and the smokestacks on factories spew oxides of sulfur, nitrogen, and carbon; a mixture of hydrocarbons; and many particulates (such as soot and smoke) into the air. In the atmosphere, sulfur dioxide and nitrogen dioxide dissolve in water vapor and form an aerosol of strong acids—sulfuric acid and nitric acid, respectively. On the one hand, some of this aerosol may drift upward, forming acidic clouds that can be blown hundreds of miles by the winds and then fall as acid rain. On the other hand, the acidic aerosol may remain close to its source as a component of the haze created by air pollution. In addition, sunlight can cause hydrocarbons and nitrogen dioxide to react with one another and form a mix of hundreds of substances called photochemical smog. The most harmful component of photochemical smog is ozone, which attacks cells and tissues, irritates the respiratory system, damages plants, and even erodes rubber. Paradoxically, the ozone that is so damaging when it is found at ground level in photochemical smog is the same compound that is beneficial in the upper layers of the atmosphere, where it prevents much of the sun’s ultraviolet radiation from reaching Earth’s surface. Unfortunately, the ozone found in smog does not make its way to the ozone layer of the upper atmosphere, because it is converted to oxygen within a few days.

When we breathe polluted air, the respiratory system is, not surprisingly, the first to be affected. As air containing toxic substances fills the lungs, cells lining the airways and those within the lungs are injured. Damaged cells release histamine, which causes nearby capillaries to widen and become more permeable to fluid. As a result, fluid leaks from the capillaries and accumulates within the tissues. Even a brief exposure to oxides of sulfur (5 parts per million, or ppm, for a few minutes), oxides of nitrogen (2 ppm for 10 minutes), or ozone leads to fluid accumulation, increased mucus production, and muscle spasms (intense involuntary contractions) in the bronchioles. These effects obstruct airflow and reduce gas exchange. Long-term irritation of bronchi by pollutants is a cause of chronic bronchitis and emphysema. The process begins when irritation causes fluid accumulation that, in turn, stimulates mucus production and coughing. The cough and mucus, signs of chronic bronchitis, irritate the lungs even more. As the bronchitis continues, the air passageways become narrower, trapping air in the lungs. When the increased pressure accompanying a cough causes the overinflated alveoli to rupture, emphysema begins.

With so many documented health consequences of air pollution, you may wonder why the world’s great minds haven’t developed the technology to solve the problem. In fact, they have. But, unfortunately, air pollution is not just a scientific problem; it is also a social, political, and economic problem. The technology to prevent air pollution is available. For example, scrubbers can remove 90% of the particulate matter and sulfur dioxide from industrial smokestacks. However, the technology is costly.

Questions to Consider

1.     □ Are you willing to pay more for goods and services, such as food, clothing, and transportation, to offset the cost of air pollution–reducing technology? How much more are you willing to pay for low-sulfur fuels, for instance?

2.     □ Some of the strategies for improving air quality are likely to impose a certain amount of inconvenience. Are you willing to carpool, take a bus, or—better yet—walk instead of drive to improve the air quality in your community?