Clean Air -- California's Success and Future Challenges

This page last reviewed September 19, 2008.

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Speaking Notes Slide 3

Historical Slide : Temperature Inversion Layer Over LA

Speaking Notes : Pollutants from Industrialization

Historical Events


Meuse Valley, Belgium - 60 Dead and Thousands Sick


Los Angeles, California - Visibility 3 Blocks, Numerous Complaints, Watery Eyes,
Nausea and Respiratory Discomfort


Donora, Pennslyvania - 20 People and 1,000's of Animals Dead, 6,000 Ill


London, England - Killer Fog 4,000 Dead

As you can see, pollutants accumulate. What traps the pollutants is what is called a "temperature inversion" -- warm air above cooler air. So imagine a pot (i.e., a valley surrounded by mountains), add ingredients (pollutants from cars and industry), put a lid on it (temperature inversion), and turn on the heat (UV light from the sun) and you get bad air. Even with the start of controls early in the 20th Century, the build up of pollutants from industrialization led to significant public heath events. In 1930, the Meuse Valley of Belgium was our first recorded air pollution disaster. A temperature inversion trapping industrial pollutants resulted in 60 dead and thousands sick from exposure to industrial air emissions. Several other events throughout history also document loss of life and various ailments, as the result of air pollution. In 1943, California recorded its first such event.

(Note: Add information where you feel appropriate.)

  • 1948 - Donora, Pennslyvania - 20 People, Numerous Animals Dead, 6000 Sick
  • 1952 - London England - 4,000 Dead

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