"Smog could worsen across the United States in the coming decades as climate change boosts summer temperatures and makes ozone levels more difficult to control, a new study says.

Americans can expect the number of days with unhealthful air to rise 70 percent by midcentury unless emissions of smog-forming pollutants are slashed, according to a study led by the federally funded National Center for Atmospheric Research in Boulder, Colo.

Higher temperatures accelerate the formation of lung-searing ozone, the main ingredient of smog, and could set back decades of improvements in air quality, the study says. "It will hinder our progress," said Gabriele Pfister, a scientist at the center and lead author of the study published last week.

Regulators, however, could keep the warming climate from degrading air quality if they adopt stringent emissions controls, the research showed."

Tony Barboza reports for the Los Angeles Times May 12, 2014. [2]