The city of London faced a climatic disaster in 1952 known by the name of “Great Smog of London”. A severe case of air pollution resulting from excessive burning of coal by the industries and citizens shut down the city for 4 days as clouds of smog engulfed the city air which was cleared off by an anticyclone. The smog was caused due to accumulation of air borne particles mostly arising from coal burning by huge industries and partly by citizens. The smog lasted from Friday 5 December to Tuesday 9 December 1952. The smog caused thousands of deaths in London, as the situation was exacerbated by outbreak of diseases and viruses.
During the four days between the 4 and 8 December 1952 smoke measurements taken at the National Gallery in London suggested that the PM 10 concentration reached 14 mg/m3 [that’s 14 milligrams/m3, or 14,000 micrograms/cubic meter!, averaging time not specified] which was 56 times the level normally experienced at the time…” [And easily 100 times as high as levels normally seen in the US today]
City of London during the Great London Smog, 1952
Picture Source: Google
Nepal also faced a similar climate catastrophe in the March of 2021. The country was engulfed with smoke released from countless forest fires raging across different parts of the country apparently all at once. The forest fires are believed to have raged due to very dry conditions across the country which ignited the accumulated dry organic wastes on the forest floor. The resulting smog completely blocked the sunlight across many places of the country making the weather cold and dark for a period of two weeks. Government decided to shut down schools and workplaces for the time being. During the smog, the air quality deteriorated too low and the capital city Kathmandu was declared the most polluted city of the world.
Kathmandu’s PM 2.5 levels reached a maximum of 363 micrograms per cubic meter on Tuesday. The World Health Organization considers anything above 25 to be unsafe. 
Both cases of air pollution had similar causes and consequences on the places although no deaths was reported in Nepal. Health of the people was severely compromised in both cases. These events profoundly impacted the people as they shouted for reforms in the system of the nations.
Nepal Air Pollution, March 2021
Picture Source: Google
MOHP Nepal issued emergency and closed all organizations of the country requesting all the citizens to stay inside their houses and avoid direct contact with the smog. No casualty of death was recorded in Nepal.
This satellite image, acquired by one of the Copernicus Sentinel-2 satellites on March 28, shows the region near Kathmandu engulfed in smoke.
Events like these pose a serious threat to the human health exacerbating the health condition of people with COPD, Asthma and other respiratory diseases.
Table: Air quality of Different cities of Nepal during the Smog in March, 2021