At this point, {TAIL ~ diesel exhaust emissions B} are also being treated for {HEAD ~ nitrogen oxide contaminants} 
At this point , { TAIL ~ diesel exhaust emissions B } are also being treated for { HEAD ~ nitrogen oxide contaminants }
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD