What is the difference between yoga and health when combining a cigarette

Arianna wants to teach her friend Leo how to do yoga. However, Leo is smoking and says he will only do it if he does not have to put down his cigarette.  The starting position is downward dog, which requires consistent inhaling and exhaling with both hands on the ground. In order to be in proper position Leo needs to hold the cigarette with his mouth and inhale cigarette smoke instead of oxygen.

Question: considering the circumstances, would it be more or less detrimental to Leo’s health to continue doing yoga?