What's the difference between London smog and Los Angeles smog?

London smog is primarily caused by coal combustion, resulting in a sulphurous smog, while Los Angeles smog is photochemical, caused by vehicle emissions.

London smog, also known as "pea soup fog," is a type of smog that was prevalent in London, particularly during the 19th and early 20th centuries. It was caused by the burning of large amounts of coal within the city. This released sulphur dioxide and smoke particles into the air, which combined with the city's naturally damp, foggy conditions to create a thick, yellowish-black smog. This type of smog is also known as industrial or grey smog. It is characterised by high concentrations of sulphur dioxide, particulate matter, and a variety of other pollutants. The Great Smog of 1952 in London is a well-known example of this type of pollution, which resulted in thousands of premature deaths and led to significant changes in environmental policy. The impact of this pollution on health and the environment has led to significant changes in air quality management, as discussed in Impact of Pollution.

On the other hand, Los Angeles smog, also known as photochemical smog, is a different type of air pollution. It is primarily caused by vehicle emissions, which release nitrogen oxides and volatile organic compounds into the atmosphere. These pollutants react in the presence of sunlight to form secondary pollutants, including ground-level ozone and particulate matter. This type of smog is also known as summer or brown smog, due to its tendency to occur during warm, sunny weather and its brownish hue. It is characterised by high concentrations of ozone, nitrogen dioxide, and a variety of other pollutants. The smog in Los Angeles is a significant environmental issue, contributing to poor air quality and health problems for the city's residents. For more details on the pollutants involved, see Types of Pollution and Nitrogen Oxides and VOCs.

IB ESS Tutor Summary: London smog, caused by coal burning, produced a sulphurous, dense fog notable in history for its severe health impacts. In contrast, Los Angeles smog, driven by vehicle emissions and sunlight, forms a brownish photochemical smog associated with high ozone levels. Both types of smog have prompted major environmental and health policy changes.