Just to put your mind to rest, I think, the water the public water company delivers to your faucet is permitted to have 5ppm of benzene. The big soda companies do not put sodium benzoate and ascorbic acid in the same can and even if they did the odds are it would have nomore benzene than the water coming out of the tap.
According to Wikipedia, sodium benzoate is found naturally in cranberries, prunes, greengage plums, cinnamon, ripe cloves, and apples. So if an apple a day keeps the doctor away, then how many sodas does it take to keep the doctor away?
This is from Wiki:
“The International Programme on Chemical Safety found no adverse effects in humans at doses of 647-825 mg/kg of body weight per day.”
Now, how much is in soda?