Possibly related: regularly encountered concentrations of ultrafine particles (UFP) have been found to reduce or even eliminate exercise-induced release of brain-derived neurotrophic factor (BDNF) [1] [2], a response which is believed to play a key role in the neurological and psychological benefits of exercise. I suspect that this is just one branch of a larger causal web and that UFP or other correlated pollution may also be reducing some of the broader endocrine/metabolic benefits of exercise.
To the best of my knowledge, UFP levels are not routinely reported or regulated. I think this is because they pass through most filters. IIRC, some kind of multi-stage filter with a liquid medium has to be used to get an accurate count.
I don't doubt you're right but I also worry that concern over each vector for bad air could easily make us neurotic.
Many problems of this sort (e.g. wood naturally contains formaldehyde) are likely solved using plant life.
So; the solution could be cheap and affordable. I realize this seems like homespun vaguely natural medicine (no chemicals!) advocacy but this is not that.
There's a nice NASA study on the subject in my comment below.
To the best of my knowledge, UFP levels are not routinely reported or regulated. I think this is because they pass through most filters. IIRC, some kind of multi-stage filter with a liquid medium has to be used to get an accurate count.
[1] https://www.ncbi.nlm.nih.gov/pubmed/22867973
[2] https://www.ncbi.nlm.nih.gov/pubmed/21708224