WNC
I remember your astute comments from the original running of this piece. I agree that air quality would be the next step of such an analysis but is beyond my ken. Also, EIA and other energy sources don't have county by county data though the forest service does - but imagine the amount of work that would be! (How many counties are there in the US??? Im guessing 2500??)

In the biggest norwegian cities it is estimated that around half of the PM10 is because of wood burning. http://www.ssb.no/svoveln/main.html (these two in english http://www.ssb.no/english/magazine/art-2003-09-15-01-en.html http://www.ssb.no/english/magazine/art-2005-01-19-01-en.html may be of interest aswell)