Fossil fuels are coal,oil and natural gas. They are not themselves photochemical smog. That is a complex mixture caused by the action of sunlight on air containing substances released when fuels burn. Thus it is connected to fossil fuels, but it is not the same thing.
Photochemical smog
Photochemical smog can occur most anywhere. London-type smog comes from factories and the burning of coal and fossil fuels, where photochemical smog comes from hydrocarbons and nitrogen oxides mixing with sunlight.
Photochemical smog
New Zeland is famous for its photochemical smog.
Photochemical smog is a type of smog made when hydrocarbons and nitrogen oxides mix with sunlight.
Photochemical smog is caused by the action on chemicals of sunlight.
photochemical smog is formed by a complex process . photochemical smog irritates breathing passages, plants, and damage rubber,plants,and some plastics
photochemical
photochemical smog
There are two major types of smog: photochemical and industrial smog. Photochemical smog is created through a reaction by which air pollutants are struck by sunlight, and form particulate matter and tropospheric ozone. The air pollutants that are most responsible for this type of smog are nitrogen oxides (NOx) and volatile organic compounds (VOCs). Photochemical is especially a problem in areas with many cars, coal-burning power plants, and the right weather conditions. Los Angeles, CA is a city that often has to deal with photochemical smog.
http://www.wisegeek.com/what-is-photochemical-smog.htm Best I could do for you but .
Nitrous Oxide