Question

Smog is a combination of?

Answer 1

Hint: This term is related to a type of air pollution. Actually, this is fog which gets mixed with air pollutants under certain circumstances to form smog. This is a very potent source of air pollution and is very harmful for us. It is often formed out of primary ($CO_2$, $SO_2$, $NO_x$, hydrocarbons) and secondary air pollutants (ozone, PAN).

Complete answer:
Smog is typically opaque and dark fog having dust, water vapor, gases and chemical pollutants. Smog is basically of two types:
Photochemical smog: It is formed in traffic-congested cities where warm conditions and intense solar radiation are present. It mainly consists of O3, PAN and $NO_x$. It is called brown air and grey air when solar radiation is intense and lesser respectively.
London smog: This is also known as classical smog. It occurs at low temperatures and contains H2S and $SO_2$. It has a reduced environment and is dark brown. This type of smog only consists of primary pollutants and secondary pollutants have no role in it.

Note:
One important concept to note down here is of primary and secondary pollutants. Primary pollutants are the ones that are emitted directly from the sources. Secondary pollutants are formed by reactions of primary pollutants with each other. E.g., Ozone, PAN. PAN inhibits ETS and damages chloroplast.
Now some people may get confused with the term ozone, since many of us know that ozone is present in the atmosphere that protects us from harmful UV rays. It is important for us to note that ozone is of two types: Good Ozone and Bad Ozone. The ozone present in the stratosphere is ‘good’ for us. But the ozone formed by pollutants at ground level is very bad for our health. Bad ozone corrodes the heritage building surface and damages marble statues and causes numerous respiratory disorders.