National Geographic : 1970 Dec
The massive struggle to clean our air began so recently that victory seems far off. But we have taken an im portant step-we realize we must do something. In the frequently quoted words of Pogo, Walt Kelly's cartoon possum, "We have met the enemy, and he is us." One by one, the factory smokestacks stop gushing noxious smoke and gases-for it is easier to regulate one factory than it is to depollute ten thousand automobiles. But here in the United States, motor vehicles contribute nearly half our air pollution. A hundred and nine mil lion exhausts spout carbon monoxide, oxides of nitrogen, lead, and a variety of hydrocarbons. Tetraethyl lead, an additive to most gasolines, is an acknowledged poison, although experts disagree on the long-term effects of small amounts of lead in the human body. Primitive man carried about two milligrams of lead in his bones. Today's city dweller carries 50 to 100 times that amount-up to one-third of what many doctors consider dangerous. While legislators frame stringent new laws, manufac turers redouble their efforts to develop more efficient emission-control devices and less harmful fuels. What else can be done to reduce automobile pollution? Increased use of car pools and mass transit would help, say environmentalists. So, perhaps, would engines of more modest horsepower. Others feel such talk is defeat ist, except as a short-term measure, and look to new technological advances for the answer. Gasoline isn't the only fuel available. In San Fran cisco, I rode in an unusual car. Its engine burned pro pane, which gives off few pollutants. At least thirty col leges and a number of industrial firms are trying to develop low-pollution engines powered by steam, elec tricity, or natural gas (page 762).* Jet Planes Spew Tons of Water No type of air pollution is more evident than the dark streaks trailing jet airliners. By 1973 this jet smoke will virtually be gone, for airlines are modifying their engines. But jets also spew less visible pollutants. And another contribution to environmental change is, strangely, water vapor. Burn a ton of jet fuel, and you produce 11/4 tons of water; the hydrogen in the fuel combines with oxygen from the atmosphere. Some meteorologists think this has resulted in an increase in cloud cover-and a corresponding reduction in the amount of solar energy reaching the earth-since jet aircraft began to fly in the 1940's. The increase thus far has been estimated at as high as 10 percent, but no one yet knows whether it will prove harmful, nor has the effect on the world's rainfall been determined. The much-discussed supersonic transport raises fur ther important questions. Public controversy has focused on two points-economics and broken windows. But (Continued on page 753) *See "The Coming Revolution in Transportation," by Fredric C. Appel, in the September 1969 GEOGRAPHIC. 748 Like a canary in a coal mine, vege tation reacts with greater sensitivity to bad air than does man. Ozone, a toxic component of photochemical smog, severely damages half the ponderosa pines in the San Bernardino National Forest, 60 miles east of Los Angeles, ac cording to Dr. Paul R. Miller (far right), U. S. Forest Service pathologist. Ozone injured needles turn a mottled yellow, then brown (right). The weakened pines fall prey to pine-bark beetles, whose tunnels girdle the inner surface of the bark, killing the tree. Close-up of polluted air: Particles spewed from factories and automobiles, enlarged 20,000 times, speckle this photomicrograph of Los Angeles smog. The average-one billion particles per cubic foot of air-is ten times the con centration on clear days. Engineers designing control devices use such samples to understand their problem. Average particle density has not in creased appreciably in 15 years, but the area afflicted by smog has spread.