Cities are places of concentrated human activity and, if not checked, human can and do produce a lot of air pollutants from chimney in homes and factories and form car exhausts.
These pollutants are Sulfur based gases and small Carbon particles. They can mix with natural fog/mist to form smog because they make the fog denser and dirtier.
Also in good weather the particles and gasses react with sunlight to form a photochemical smog which hangs like a haze over the cities.
Both types of smog are very harmful to human health - THEY KILL PEOPLE - and can be prevented by using catalytic converters on cars and insisting all fuels used in cities are smokeless and that factories scrub their exhaust fumes of pollutants before exhausting them to the air.
This was a lesson learned in Europe during the Industrial revolution. Sadly the developing world does not seem to be learning form these experiences.
smog is air pollution it is smoke caused by factories
Smog is made up of various pollutants produced in cities. These pollutants can include carbon dioxide, ozone, methane, and other harmful gases.
Photo chemical smog
sunny cities
smog
The hazy clouds that hang over some cities is called smog
cities are affected by smog
smog
The smog mainly hits cities. This shows that cities create more pollution.
Unfortunately,all the major cities of the world are affected by smog.
in cities and industrialised areas are highly polluted with smog
Smog
The word is "smog", a pollutant mix common to many cities worldwide. Smog was a primary reason for research into catalytic converters for automobiles.
Smog abatement means reducing the amount or intensity of smog.