We are many who will run in the sunset zone for being in shape or wasting the stress of the day. We have often had to ingest in our runs the orange hollines of a bus or car when our lungs asked for clean and fresh air.
We had the intuition of what could not be good for health. This has now been cited in a study conducted in the US. And those who run in contaminated environments capture the harmful effects of dirty air at the same level as smokers.
Therefore, we will have to take into account where we are running, if we want the sport to be good.