Why are components that are naturally found in air be considered air pollutants?

It is because components of air like carbon dioxide can be considered as a pollutant when the concentration of these gases is larger than the normal range due to human activity like the burning of fossil fuel. At a higher concentration, even the naturally occurring gases may have an undesirable effect on the environment. The high level of carbon dioxide can cause an increase in the earth's temperature.

the cost of mining is extremely low compared to the money earned from mining, creating income to improve the environment.