I dont know the number but its something ridic, like in the double digits, of wood burning homes left in UT.
I just looked it up...something like 43 (as of 2014- I am sure it is less, since we've aggressively gone after converting those people.). Yes, its a problem but it sure not our biggest problem.
The solution is: 1) Cars/trucks. 2) Buildings. Period. That accounts for about 75% of all the particulates in the air.