Clear skies dawned over London on December 5, 1952. A wintry cold snap had gripped the British capital for weeks, and as Londoners awoke, coal fireplaces were stoked in homes and businesses across the city to take the chill from the early morning air. Because of economic necessity, most higher-grade hard coal was exported, so Londoners were forced to burn lower-grade coal high in sulfur. At this same time. London was hit by a thermal inversion, in which a layer of warm air settles over a layer of cooler air that lies near the ground. The warm air holds down the cool air and prevents pollutants from rising and scattering.
Later in the morning, the fog began to roll in. Londoners paid no attention, since fog was not unusual in a city famous for its cool, misty weather, however , within a few hours, the fog began to turn a sickly shade of yellowish brown as it mixed with thousands of tons of soot pumped into the air by London’s factory smokestacks, chimneys and automobiles. Adding to the toxic brew were the exhausts from the smoky, diesel-fueled buses which had recently replaced the city’s electric tram system.
The temperature inversion prevented London’s sulfurous coal smoke from rising, and there was no wind to disperse the soot-laden smog. The noxious, 30-mile-wide air mass, teeming with acrid sulfur particles, reeked like rotten eggs and continued to thicken throughout the night, and reducing visibility to near zero.
Some drivers abandoned their cars; still others had a passenger walk five yards ahead with a flashlight. By 2pm next day, London was practically in total darkness, and many people decided to stay inside. However, yellow tendrils of the poisonous fog began to seep into homes, and by Dec 7, the weakest members of London’s population began to succumb. These included the young, the old, and those who already sufffered with with respiratory problems. Symptoms included nausea, hacking cough, and bluish skin caused by oxygen deprivation.
On Dec 9th, conditions finally changed and the smog began to blow away. By that time, though, there were so many deaths that there was a ten-day waiting period for burials. Officials estimated that some 4000 people died as a direct result of the killer smog, and around another 3000 succumbed later, usually from respiratory complications.
The 1952 killer fog is still considered the worst air pollution event in European history, and eventually it led to the passage of the Clean Air Act in 1956.