Smog is an intense air pollution which is made by the combination of smoke and fog it’s a thick grey haze that covers the atmosphere. Smoke from burning coal, home stove, industrial smoke altogether combines with the moisture in the air. The yellowish smog is different from the normal smog.
Volatile organic compound (VOCs) and nitrogen oxide VOC are compounds that easily become vapors and may contain elements such as carbon, oxygen, hydrogen, chlorine and Sulphur. Some are naturally produced by plants and animals but other comes from manmade sources like solvents, paints, glues and petroleum.
Meanwhile the incomplete combustion of gas in motor vehicle releases Nitrogen oxide that’s gives the yellowish color to the smog. VOCs and Nitrogen oxide reacts with sunlight to produce secondary pollutants called the PANs and triphosphorous or ground level ozone. PANs and Ozone cause eye irritation and damage lung tissue both are key ingredient in photochemical smog.