Related Clues:

• Pollution portmanteau
• Clean air hurdle
• Possible cause of heavy breathing
• Visibility obstacle
• City haze
• L.A.'s haze
• Sight inhibitor, often
• L.A. issue
• Exhaust issue
• Cause of some urban coughs
• Air woe watched by the EPA
• Visibility obstructer
• Urban health problem
• Freeway byproduct
• Air quality concern