What are the harmful effects of photochemical smog and how can they be controlled ?

The common components of photochemical smog are ozone, nitric oxide, acrolein,formaldehyde and peroxyacetyl nitrate ($PAN$).

Photochemical smog causes serious health problems. Both ozone and $PAN$ act as powerful eye irritants.

Ozone and nitric oxide irritate the nose and throat and their high concentration causes headache, chest pain, dryness of the throat, cough and difficulty in breathing.

Photochemical smog leads to cracking of rubber and extensive damage to plant life. It also causes corrosion of metals, stones, building materials, rubber and painted surfaces.

Many techniques are used to control the formation of photochemical smog. Some of the techniques are as follows :

If we control the primary precursors of photochemical smog, such as NO $_{2}$ and hydrocarbons, the secondary precursors such as ozone and $PAN$, the photochemical smog will automatically be reduced. Catalytic converters are used in the automobiles, which prevent the release of nitrogen oxide and hydrocarbons to the atmosphere.

Certain plants e.g., Pinus, Juniparus, Quercus, Pyrus and Vitis can metabolise nitrogen oxide and therefore, their plantation could help in this matter.