Thanks for raising this; it was a question of mine, too.  I believe there have been studies linking industrial/motor noise with chronic/continuous release of stress hormones (cortisol, adrenaline) which, of course, leads to chronic inflammation and the havoc that wreaks on the human organism: neurological, immune, circulatory, etc...
There are many kinds of pollution that affect us and other organisms/systems.  We would be wise to consider them all.