It's cost billions of dollars and dozens of lives.

In countries where diesels are popular, the extra ozone pollution could add up.

The pope is likely to preach about climate change and economics when he is in the U.S.

Cities in India have air that's four times deadlier than Beijing's.

Agency is forbidden from taking costs into account when writing rules like one proposed this week that would lower amount of smog-causing ozone allowed in the air.

The U.S. and China are drawing a line in the sand on greenhouse gas emissions.

Why reducing acid in rain is just the first step in recovery.

Fabien Cousteau will spend 31 days living in an underwater laboratory