the smoke in london smog came primarily from
Smog Coal fires, used to heat individual buildings or in a power-producing plant, can emit significant clouds of smoke that contributes to smog. Air pollution from this source has been reported in England since the Middle Ages.[3][4] London, in particular, was notorious up through the mid-20th century for its coal-caused smogs, which were nicknamed 'pea-soupers.' Air pollution of this type is still a problem in areas that generate significant smoke from burning coal. The emissions from coal combustions are one of the main causes of air pollution in China.[5] Especially during autumn and winter when coal-fired heating ramps up, the amount of produced smoke forces some Chinese cities to close down roads, schools or airports. One prominent example for this was China's Northeastern city Harbin in 2013.