Related Clues:

• L.A. issue
• Exhaust issue
• Cause of some urban coughs
• Corrosive stuff from the sky*
• Air woe watched by the EPA
• Visibility obstructer
• Urban health problem
• Freeway byproduct
• Air quality concern
• Beijing problem
• Air condition
• Air that makes you go [cough, cough]
• Air problem
• Target of clean air laws
• Unhealthful skyline obscurer