Among the large cities, there are six megacities (population above 10 million people), 12 extra-large cities (population of 5 10 million), 21 Type I large cities (population of 3 5 million), and 164 Type II large cities (population of 1 3 million) [1].
The air quality challenge of megacities (population >10 million) has received considerable attention.The 20 megacities in this data set account for ∼15% of the total city population (300 million people) and have a population-weighted mean iF of 83 ppm (IQR = 48 94 ppm, range 25 260 ppm).
It will really impact megacities, populations and water availability".
When Yun Jae Lee's family left Seoul, South Korea, one of the world's glittering megacities, with population of more than 10 million, it was to Whangarei, the small Northland city with a population of 50,000, that they moved.
The number of "megacities"—with populations in the tens of millions may grow to several hundred by the middle of the 21st century.
By that year, business consultant McKinsey and Co predicts, there will be 68 Indian cities of more than a million people, 13 with more than 4 million and six megacities with populations of 10 million or more.
Urbanisation which took place over a period of several decades in Europe and North America is happening in just a few years in East Asia, which already contains eight megacities (with populations above 10 million) and 123 cities with between one and 10 million people.
By 2015, there will be 21 megacities with populations over 10 million, according to UN estimates.
The situation is even worse in megacities, whose populations are greater than 10 million.
Mumbai's problems are characteristic of a new breed of fast growing megacities where populations are measured not just in millions, but in tens of millions and growing rapidly.
The Metropolitan Region of Santiago de Chile (MRS) is a typical Latin American megacity, showing population growth over the last years as well as a rising standard of living, associated with an increase of the gross domestic product (GDP) from US$10,000 to US$14,000 per capita in about 10 years.
