What is smog and how can it be prevented? © Getty Images

What is smog and how can it be prevented?

A combination of the words ‘smoke’ and ‘fog’, the term emerged around a century ago to describe the dense, choking mix of gases and soot that was becoming common in big cities.

Asked by: Samuel Lennox, Reading

Advertisement

A combination of the words ‘smoke’ and ‘fog’, the term emerged around a century ago to describe the dense, choking mix of gases and soot that was becoming common in big cities. Back then, smog was generated by coal-burning homes and factories spewing out a potentially lethal cocktail of ozone and oxides of carbon, sulphur and nitrogen. The Great Smog of London in 1952 killed over 4,000 people.

Today, houses and factories have been replaced by traffic as the principal cause of smog. Last March, driving restrictions were imposed in Paris, which suffers worse than other European capitals because of the popularity of cars running on cheap but dirty diesel. The problem is especially severe in sunny weather, when the sunlight interacts with pollution to produce a noxious ‘photochemical’ smog.

Yet the world leader in smog production is China. The pollution from its quarter of a billion cars has been implicated in around three million pollution-linked deaths each year, with China’s own scientists describing Beijing as “close to uninhabitable”. In May, the Chinese government announced it was going to attempt to control smog by curbing car use in Beijing, and by scrapping over five million old, heavily-polluting cars.


Advertisement

Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.