Climates wise Hanoi is probably comparable to Shanghai. Seems that more factories have relocated from China to Vietnam, specifically outside of Hanoi. Hence when comparing the airs between the two cities, people in Hanoi should be shocked. See below:
Remember, readings inside homes and apartments will be higher than outside.
Below is the same reading currently in Shanghai. I have not turned on my air purifier in the living room yet so it equals the air quality outside. My bedroom has an air purifier on all night.
Again many in Shanghai are surprised the air quality has been lower but many think it is due to the factories being moved to Vietnam.
Below are readings in the region. Seoul gets high pollution at times and Fukuoka should get affected as well by the pollution in China.
I short, Hanoi is now very polluted.
I am trying to figure out ways to bring the affordable filters to Vietnam which can be cheap to ship. I just need to find a suitable fan in Vietnam.
I will keep you all updated.