The pieces to the puzzle had fallen into place. Ozone has a bleach-like smell, and it destroys plants and rubber products. Los Angeles had plenty of cars to supply nitrogen oxides and VOCs. And the famous California sunshine was the perfect catalyst for the chemical reactions that form ozone.
One piece of the puzzle was still missing: Why did Los Angeles have more of this kind of smog than other major cities? The answer was a matter of geography and topography. Los Angeles is surrounded by mountains, which trap VOCs and nitrogen oxides in the valleys where people live and breathe. By the early 1940s, Los Angeles had all of the ingredients for catastrophic smog events, which plagued the city for more than half a century.
Taming the culprits of smog
Haagy’s findings were published in 1950, and his fellow researchers confirmed in 1955 that ozone from VOCs and nitrogen oxides was at the root of the Los Angeles smog. But when gasoline and cars were identified as the primary pieces of the smog puzzle, researchers pointed a finger at our beloved automobiles, a fundamental part of the American dream.
It took years of politics, policy, and innovation to reduce the emissions of VOCs and nitrogen oxides that make ozone. Enforcement of local laws was difficult because air pollution does not heed city and country borders. Regulations to reduce air pollution quickly became a state, as well as a national, issue and eventually led to the Clean Air Act, passed by Congress in 1970.
While legislators were writing regulations, the petroleum and auto industries were innovating. Oil companies reformulated gasoline to burn more efficiently, reducing the amount of unburned VOCs in car exhaust. Gas stations put sleeves on gas pump nozzles, reducing the amount of VOCs evaporating from gasoline.
Regulations prompted the automobile industry to make more fuel-efficient cars and to develop catalytic converters that reduced the amount of nitrogen oxides and VOCs—along with carbon monoxide—released from cars. Similar technologies, such as selective catalytic reduction devices, were designed to reduce the amount of nitrogen oxides released from power plants.
Tracking puzzle pieces from space
Air pollution is not just confined to Southern California; it is produced wherever people burn fuel for energy. It is dispersed by the wind over long distances, across state and country borders. So, to monitor concentrations and distributions of pollutants, we need a global view. In 2004, NASA launched several remote sensing instruments onboard the Aura satellite that can observe the air quality of the entire planet in just 24 hours.