Dirty air

Air pollution, in the form of smoke, has been in existence throughout antiquity. The onset of the industrial revolution in the 17th century heralded a more lethal form of air pollution as man-induced emissions increased. In London, for example, episodes of stagnant smoke combined with dense fog became more frequent, causing severe health problems such as pulmonary disease and heart failure. More recently, in Los Angeles, US, in the late 1940s and early 1950s, a dense haze, later referred to as a photochemical smog, was observed. These smogs caused eye irritation, sore throats, asthma and other respiratory problems. Here we take a look the primary and secondary air pollutants responsible for these combustion and photochemical smogs.