What is "smog" and how does it affect air quality?

What is "smog" and how does it affect air quality?

Terry Tamminen (Author & Environmental Policy Advisor) gives expert video advice on: Is there a correlation between smog and human disease? and more...

Smog was a term that was first coined in the late 1800s in England when researchers observed a combination of smoke and fog -- smog. Since then, we've understood that the smoke from smog doesn't always need a lot of moisture, doesn't need the fog part. In a modern American city, or anywhere else around the globe, the smog is caused mostly by emissions from motorized vehicles, although certainly some of it is caused by emissions from power plants and other things that burn fossil fuels.