Comparing pollution levels between the two megacities, home to a combined 29 million people, seems natural given their iconic status representing Asia's opportunity and growth. They both have gone through breakneck economic development that has transformed their landscapes within a generation, raising living standards but also spewing out loads of pollution.
Decades of policies that favored economic decisions over environmental concerns have taken their toll. Cars now represent the middle-class dream for thousands digging out of poverty, and decades of booming construction has kicked up countless clouds of dust.