Answer:
The main cause of smog in the urban areas of London historically was the burning of coal for heating and industrial purposes. This type of smog, known as "London smog" or "pea-souper fog," was prevalent in the 19th and early 20th centuries. It occurred when coal smoke combined with fog, creating a thick, choking mixture of pollutants that severely reduced visibility and had harmful health effects.
The specific mechanism involves the release of sulfur dioxide (SO2) and particulate matter from the combustion of coal. These pollutants would mix with moisture in the air, forming sulfuric acid droplets and fine particulate matter. When these combined with natural fog, the result was a dense and toxic smog.
In response to the severe health and environmental impacts of London smog, the UK implemented various measures to reduce coal burning, including the Clean Air Acts in the mid-20th century. These measures helped transition the city away from coal as a primary source of heating and energy, leading to significant improvements in air quality.
Today, London and many other urban areas face air quality challenges primarily associated with traffic emissions, including nitrogen oxides (NOx) and particulate matter from vehicle exhaust. While coal burning is no longer a major source of smog in London, modern smog or air quality issues are often linked to vehicle emissions and other industrial sources.
Culled from AI