I have a bio-chem degree and most everything is touched by organic solvents these days. It is all about using the cleanest solvents and taking your time to remove all contaminants from the final product.
Most of us city dwellers are breathing car exhaust and tire dust that is much more toxic than most BHO. My whole house air filter is covered with a quater inch of black dust after six months.
I would still rather be smoking Matt's full melt bubble though
Here is an update of the Malawi Gold:
Cheers,
Mo