16 Reasons to Avoid Soda - What Happens to Your Body When You Drink Soda

Benzene: 
Benzene is a possible cancer causing substance that is found in small levels in some types of soda. It has been linked to leukemia. (8) Benzene levels in bottled water are monitored and regulated. But levels in soda are only monitored informally, which means the exact levels may not be known. Benzene forms due to the presence of benzoate salts, which are used as a preservative, and ascorbic acid, which is in certain carbonated soft drinks.