US proposes stricter ozone limits

The US Environmental Protection Agency announced plans Wednesday to strengthen emission regulations for ozone, a smog-causing pollutant blamed for respiratory ailments affecting millions of Americans.

But the measures prompted immediate criticism from Republicans and industry groups, who said they would be too costly, without much benefit.

Recent scientific studies, the EPA said, show current standards leave too much harmful smog in the air.

Exposure at those levels, and at levels below the current maximum, "can pose serious threats to public health," including causing asthma and other lung diseases and can even be linked to death from respiratory and cardiovascular causes, the agency said.

"Bringing ozone pollution standards in line with the latest science will clean up our air, improve access to crucial air quality information, and protect those most at-risk," EPA Administrator Gina McCarthy said in a statement.