None whatsoever! The smoke ring is caused by the nitrates created by burning wood. This will even happen with a very clean burning fire with no visible smoke at all. A 'smoke' ring also can be artificially created using Morton's Tender Quick or some other tenderizer containing nitrates.
Mister Bob, Pitmaster - Bob's Hogs. KCBS CBJ #31759 - IMBAS Certified MOINK Baller