Shortness of breath is something doctors report as a more and more common symptom of city dwellers.
Not reported on the news because nobody -- apparently you included -- cares, but I've been to doctors lately, and they complained that the lung and heart doctors are overbooked lately while the others have a normal load.
Generally, it takes a lot of pollution to counter the positive health effects of active commuting. It was a while since I did the research, but someone estimated that you need to cycle for more than sixteen hours per day for the pollution to outweigh the cardio benefits in the 90th percentile of cities ordered by pollution. There was no city for which any mount of cycling would have made you worse off.
Granted, walking is probably slightly lower in intensity, but still.
So yeah we gave up and just go eat out. :|
So not only is the air bad, the walkable places are few and far between, strongly discouraging people to even go where the better air is or, as you said, just have the cardio from walking/cycling to improve your health.
It’s been 15 years I commute daily by bike and worry about the side effect on my lungs… sometimes the road stinks so much, especially when too much trafic jam. Trying to slow my pace to breathe « less deep » but not a fun things to do.
Likely the same extended lifespan that's been prevalent in Japan over the past century of smoking, diesel and construction (along with the occasional nuclear catastrophe). Humans are apparently more ruggedized than they look on paper.