from what I understand, it is. There have been a few really good posts on the topic in the last year - I can't tell ya exactly, but it isn't really the smoke, but the heat causing a reaction with a chemical or chemicals in the rub. I'm sure someone will post a better explanation.
IMBAS Certified MOINK Ball maker and IMBAS Sgt. At Arms.
And now, brethren, I commend you to God, and to the word of his grace, which is able to build you up, and to give you an inheritance among all them which are sanctified. [Acts 20:32 KJV]