Pea soup fog

Pea soup fog (also known as a pea souper, black fog or killer fog) is a very thick and often yellowish, greenish or blackish fog caused by air pollution that contains soot particulates and the poisonous gas sulphur dioxide. This very thick smog occurs in cities and is derived from the smoke given off by the burning of soft coal for home heating and in industrial processes. Smog of this intensity is often lethal to vulnerable people such as the elderly, the very young (infants) and those with respiratory problems. The result of these phenomena was commonly known as a London particular or London fog; in a reversal of the idiom, "London particular" became the name for a thick pea and ham soup. From as early as the 13th century, air pollution became increasingly prevalent, and a predominant perception in the 13th century was that sea-coal smoke would affect one's health. From the mid-17th century, in British cities, especially London, the incidence of ill-health was attributed to coal smoke from both domestic and industrial chimneys combining with the mists and fogs of the Thames Valley. Luke Howard, a pioneer in urban climate studies, published The Climate of London in 1818–1820, in which he uses the term "city fog" and describes the heat island effect which concentrated the accumulation of smog over the city. In 1880, Francis Albert Rollo Russell, son of the former Prime Minister Lord John Russell, published a leaflet that blamed home hearth smoke, rather than factories' smoke, for damaging the city's important buildings, depriving vegetation of sunlight, and increasing the expense and effort of laundering clothes. Furthermore, he charged the "perpetually present" sulphurous smoke with increasing bronchitis and other respiratory diseases. More than 2,000 Londoners had "literally choked to death", he wrote, on account of "a want of carefulness in preventing smoke in our domestic fires" which emitted coal smoke from "more than a million chimneys" that, when combined with the prolonged fogs of late January and early February 1880, fatally aggravated pre-existing lung conditions and was "more fatal than the slaughter of many a great battle".