The Dangers of Photochemical Smog

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This essay investigates a chemical issue faced in society today of a social or environmental nature. By exploring two different perspectives of the issue conclusions are formed based on the collated information using appropriate chemical terms where necessary (e.g. chemical equations).

In recent times largely populated cities are becoming increasingly susceptible to photochemical smog. Toxic grey fog is produced by transport, factories and other high pollution producing industries which are concentrated in one particular area. This essay highlights how pollution is produced, reduced and what we can do.

Photochemical smog is the result of primary and secondary pollutants, such as carbon monoxide (CO), nitric oxide (NO), ozone (O3) and sulphuric acid (H2SO4), concentrated in one area. These pollutants are toxic to humans and other organisms, reducing oxygen levels in the air. Extended exposure can lead to irritation of the eyes and respiratory system and even death.

Primary pollutants are molecules that are directly emitted into the atmosphere (Morton, B. Essen. Wrkbk.). Transportation, a common producer of primary pollutants, is proportionally the reason why large cities, such as Milan (Italy), Mexico City (Mexico) and Linfen (China), experience a haze during the day (http: (2)). In a car’s internal combustion chamber reactions taking place create energy. If oxygen supply is limited incomplete combustion occurs, less energy is released, and unwanted molecules form. Examples of primary pollutants are carbon monoxide, carbon (fine particle soot) and unburnt hydrocarbons.

The combustion of cyclohexane, a fuel constitute used in cars:

C6H12(l) + 9O2(g)  6CO2(g) + 6H2O(l) ∆H = -3916 kJ mol -1

Incomplete com...

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...bove equations of CO and NO removal). This is why plants are important in the removal of carbon dioxide in the environment to restore higher oxygen levels. The process plants use to remove carbon dioxide to be replaced with oxygen and energy (carbohydrates) for their growth is called photosynthesis. Cities can produce much needed oxygen by planting trees within a close proximity.

Photosynthesis in plants:

nH2O + nCO2  (CH2O)n + nO2

(Stanley, R. Discovering Chem.)

The complex environmental issue of photochemical smog is on the increase as towns and cities are always growing. This essay explained that primary and secondary pollutants, mainly produced through cars, are responsible. It also explored ways at which primary pollution can be reduced. This issue can only be resolved if everyone works together to stop it. So what will you do?
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