Photochemical smog consists mainly of what?
carbon
acid
oxygen
ozone
Secondary pollutants form from primary pollutants. Many occur as part of photochemical smog . This type of smog is seen as a brown haze in the air. Photochemical smog forms when certain pollutants have a chemical reaction in the presence of sunlight. Photochemical smog consists mainly of ozone (O 3 ). Ozone near the ground is a pollutant ( Figure below ). This ozone is harmful to humans and other living things. However, ozone in the stratosphere protects Earth from the Sun's harmful ultraviolet radiation.