Emissions may be down, but you might not know it considering Southern California smog has worsened for the second year in a row. So far this year, 145 days have violated federal health standards for ozone levels.
Ozone comes about when pollution chemicals bake in warm air. The particles from the process have been known to cause health complications.
Air health experts contend that the past two years have been unusually warm, resulting in more harmful ozone than in recent years.
"You have these weather patterns that settle in. You get these multi-day episodes of heavy smog when you get high heat and stagnant air," LA Times reporter Tony Barboza explains to Take Two.
"We've clamped down so much that we're seeing what you would call 'diminishing returns' as time goes on after many years of progress battling smog."