Population, population density, automobiles, and lingering effects of recent poverty. London's metro population peaked around 9 million right around 1940, alth

Population, population density, automobiles, and lingering effects of recent poverty. London's metro population peaked around 9 million right around 1940, although it's back up to similar numbers. The population of manhattan peaked around 2.3 million in the 1920s. The population of Beijing, Guangzhou, or Shanghai are all about 20 million plus. There were fewer automobiles in London even in the mid 20th century than there are in the big Chinese cities today (there are over 5 million cars in Beijing alone). Many of those automobiles are either diesel powered trucks, buses, and cars or 2-stroke scooters and motorcycles, all of them highly polluting. Add to that the heavy reliance on coal for home heating and cooking and you have the pollution nightmare that is now quite evident. The population of the entirety of the UK was only 50 million in 1950, and the population of the US in 1950 was only 150 million. Today in China nearly 50 million people live in Guangzhao alone, and over 100 million people live in the top 4 largest municipalities, within an area that is in total similar in size to Los Angeles county. And the pollution contribution from the population of more than a billion who often live near the major cities is also not inconsequential.