Benzene, a known carcinogen, has been found in a number of soft drinks at concentrations far in excess of the legal limit for drinking water. Various regulatory agencies around the world have set upper limits for benzene in drinking water between 1 and 10 parts per billion (ppb). However, recent tests by an independent New York laboratory found benzene concentrations several times higher than 10 ppb. In the 1990s, Perrier sparkling water was recalled when benzene was found at concentrations lower than those reported for the soft drinks, but no recall was ordered this time for the offending drinks.

It has been known for at least 15 years that that sodium benzoate (a preservative) and ascorbic acid can react in drinks to form benzene. The formation of benzene can easily be prevented by not adding sodium benzoate to drinks that contain ascorbic acid.

Comment: In the past, the soft drink industry was successful at keeping benzene out of beverages. However, according to an industry spokesman, "there are a lot of new companies, a lot of new brands, and things have changed." It's like the old Steve Martin routine:
Judge: "Didn't you know it is against the law to rob a bank?"
Defendant: "Yes, your honor, I did, but I forgot."
Almost makes you want to stop drinking sugary, acidic, artificially colored drinks.

Mercer C. Soft drinks industry pledges to tackle benzene in drinks. http://www.beveragedaily.com/news/ng.asp?n=66084-benzene-soft-drinks-aba. Accessed April 5, 2006.