I'm aware of quite a bit of emissions data being collected on rocket stoves, showing that they are much, much cleaner than almost all stoves out in the world today. Peter van der Berg (sp?) has the equipment and has brought it to multiple innovator's events at Wheaton Labs.
Now, I don't think you can remove the toxicity produced when burning toxic wood, at least not elemental toxicity like arsenic or lead. . . . A well built rocket mass heater is incinerating the fuel, not just burning it, so most hydrocarbon toxins would be wiped out, but elements are elements, at least until you put them in the nucleus of a star, or something similar.