The Killer Smogs
On the night of December 1, 1930, a dense fog moved over the Meuse Valley, in Belgium. Many factories in the valley poured smoke and fumes into the foggy air. This created a dark smog of smoke and fog combined. People in the valley began to cough and train for breath. The smog remained for four days. During that time, thousands of people became ill. The hospitals were filled with patients. Sixty people died. Most of them were older persons with heart and lung problems. Finally, a heavy rain washed away the smog. Scientists studied the causes of the disaster. They concluded that the illnesses and deaths were caused by chemicals in the smog.
The first reported event of this kind in the United States happened in Donora, a factory town in a valley near Pittsburgh. In 1948, a killer smog made half of the population sick, there were 17 deaths. Again, older people with lung or heart diseases were hit hardest.
London, England, has always been known for its "black fogs." In the winter of 1952, a milky white fog rolled into the city. It soon turned into black smog as the smoke of the city poured into the air. It was so hard to see that people had to walk in front of the buses to guide them. In this way, the most serious air pollution disaster in history began. When it was over, more than 4,000 people had been killed by the thick black smog.
New York City has had several London-type smogs since 1950. Each time, there were from 100 to 400 deaths caused by the smog. Although these smogs were not as deadly as London's, New York City has the worst air pollution problem in the United States.
In all the killer smogs, factories and homes poured smoke and fumes into the air from the furnaces. The chemical fumes combined with the water droplets in the fog to form harmful substances. These substances caused the illness of those who breathed the polluted air.
Usually, such harmful fumes rise into the upper air and are blown away by the wind. But sometimes there is an unusual weather condition called a temperature inversion. A layer of cold air remains near the ground as smoke and fumes pour into it. This is covered by an upper layer of warm air that acts like a lid. It prevents the polluted cooler air from rising. The harmful fumes pile up and make people ill. The smog may be so thick that airports are closed and chains of collisions occur on the highways.
Another type of smog occurs in Los Angeles. Here the weather may be clear and sunny. But stinging eyes and dry coughs show that harmful chemicals fill the air. The smog is due to invisible gases, mostly from automobile exhaust. Because these chemicals are changed by the sun high up in the air, Los Angeles smog is called photochemical smog. It contains automobile exhaust fumes and nitrogen oxides changed by the sun's rays. Added to these are sulfur dioxide and other fumes from factories and oil refineries. Photochemical smog is found in many large cities all over the world.
Killer smogs don't happen very often, fortunately. But in many large cities, a combination of automobile exhaust fumes, home furnace smoke, and factory waste gases pours into the air. This may also happen in the suburbs, or out in the country, where large factories have been built. A number of harmful substances have been found in the air there. When these substances are breathed in day after day, the health of the population is affected.