Urban atmosphere London smog

Approximately half of the world s population now lives in urban areas, and half of these people suffer an atmosphere containing harmful amounts of substances such as sulfur dioxide, ozone, and particulate matter. Approximately 4000 people died from lung and heart conditions during a London smog episode in December 1952. Globally, around 50% of cases of chronic respiratory illness are now connected with ah pollution. The most... 

We saw in Section 3.6.1 that the acid-laden smoke particles in the London atmosphere caused great harm to human health in the past. Pollutants in the atmosphere still cause concern because of their effect on human health, although today we need to consider a wider range of potentially harmful trace substances. The photochemical smog encountered ever more widely in modern cities gives urban atmospheres that are unlike the smoky air of cities in the past. Petrol as a fuel, unlike coal, produces little smoke. 

Here we should compare the visibility decrease due to particulates concentration in urban air, so called London smog, with a similar atmospheric phenomenon, Los Angeles photochemical smog. 

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