Oxides of sulfur, small particles, traces of heavy metals, polycyclic aromides . . . it's all there!  

(Not much oxides of nitrogen though.)  

Yes the switch to diesel received universal accolades for being clean!  

This locomotive never burned wood, and could not.  The tip-off is the smoke stack, which is so small and short it is almost invisible.  Wood burners require large, fat stacks that hold the screens that filter out the burning embers--without which you would be setting grass and forest fires all along your route as you chugged merrily along.  

The thick smoke shows the fire in the box has been freshly stoked.  As the coals burn down the smoke they put out can decline nearly to invisibility (in a photo like this.  It never really falls to nothing.)  

The Fates are kind.