Related Clues:

• Not quite a fog
• Exhaust issue
• Cause of some urban coughs
• Thick haze
• Air woe watched by the EPA
• Visibility obstructer
• Urban health problem
• Freeway byproduct
• 'Gorillas in the ___'
• Spray-can output
• London weather
• Navigation problem
• ___ of war
• Gentle spray
• Air quality concern