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.
Photo chemical smog
smog
cities are affected by smog
The hazy clouds that hang over some cities is called smog
Unfortunately,all the major cities of the world are affected by smog.
in cities and industrialised areas are highly polluted with smog
That is known as smog, a mixture of pollutants, primarily from vehicle emissions and industrial activity, that can create a visible haze over urban areas.
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
London-type smog typically forms when particles in coal smoke react with sunlight and humidity to create a harmful mix of pollutants like sulfur dioxide and nitrogen oxides. This type of smog, also known as sulfur smog, was prevalent in industrial cities like London before clean air regulations were enforced.
Smog abatement means reducing the amount or intensity of smog.
I don't think smoggish is a word, but smog is?