Question

Any kind of substance released into the air from natural or human sources — discharge of gases, liquid droplets or solid particles, is called ............... .

Hint:

Tip: Anything harmful added to air → pollutant!

Answer 1

A pollutant is an environmental contaminant that causes harm.
Atmospheric discharges of gases, vapors, dust, liquid droplets, or solid particles degrade air quality.
These substances can originate from natural events such as volcanic eruptions and dust storms, or from human activities including vehicle emissions, industrial processes, and the combustion of fossil fuels.
Examples of pollutants are CO₂, SO₂, NOx, particulate matter, and hydrocarbons.
They are contributing factors to smog, acid rain, respiratory illnesses, and global warming.
While "residue" and "by-products" are broad terms, they are classified as pollutants when introduced into the air and negatively impacting the environment.
Consequently, the appropriate term is pollutant.