Southern California smog worsens for second straight year despite reduced emissions

LOS ANGELES - For decades, Southern California has waged a slow but successful war on smog. Through vehicle emissions rules, clean-fuel standards and other tough measures, officials have lifted the choking pall of air pollution that once shrouded Los Angeles, bringing clearer skies and healthier lungs.

But now, progress appears to be faltering. Smog has gotten worse for the second straight year, even though emissions are on the decline.

That apparent disconnect is forcing regulators to explain why air quality in the nation's worst-polluted region is dipping.

Ozone, the harmful gas in smog that inflames the lungs and triggers asthma attacks and other health problems, has violated federal health standards 145 days this year across Los Angeles, Orange, Riverside and San Bernardino counties, air monitoring data show. That's up from 132 ozone violation days last year and 113 in 2015.

The South Coast Air