Elana44 asks…I’ve recently heard that sodium benzoate when met with ascorbic acid (vitamin C) can lead to cancer and damage DNA. Is it true?
The Left Brain responds:
September must be national benzene month. Last week the Right Brain blogged about benzyl benzoate making fragrances smell like vinyl. And today I get to field a toxicology question. So today’s post is for all you benzoate boosters out there.
Why is sodium benzoate in my cosmetics and can it really form benzene?
Sodium benzoate is a preservative that helps protect your creams and lotions from micro-organisms. This story has it roots back in 2005 or so when trace amounts of benzene where discovered in a variety of soft drinks. Benzene is a found in a variety of petrochemical products (like emissions from burning coal and oil, gasoline service stations, and motor vehicle exhaust) and in cigarette smoke. In this case the benzene was apparently being generated by the decarboxylation of the benzoate by ascorbic acid. This was of concern because benzene has been linked to several types of cancer.
The FDA investigated and found that most of the soft drinks had less benzene than is allowed in water. (The FDA sets limits for water but not other beverages.) The limit for water is 10 parts per billion (ppb). (Remember we’re all exposed to chemicals that at low levels are perfectly safe – the dose makes the poison, as they say.) The soft drink manufacturers that were exceeding the 10ppb decided to reformulate their products and those have now dropped to much lower levels. So for now, there doesn’t appear to be any concern for soft drinks. But what about cosmetics?
Definitive data is needed
Vitamin C lotions certainly can contain sodium benzoate. But since no one’ published data we don’t know if these cosmetics undergo the same reaction that occurs in beverages. Since we know that sugar inhibits the creation of benzene, it’s possible that similar ingredients in cosmetics (like sorbitol) could have the same effect.
Since no one has done a definitive study on cosmetics (that I’m aware of) we don’t know what the benzene levels are. (Perhaps individual manufacturers have tested some of their own products. If they have it would be nice if they would share that data.) It’s difficult to guess, but it seems doubtful there’s much to worry about. We know that the pH has to be below 2 for benzene formation to occur and not many cosmetic products are in that ranges. Even if small amounts are formed, there’s less risk to you than if you were ingesting the same amount (because it won’t all penetrate your skin.)
The Beauty Brains bottom line
Ok, lots of info here but what to do? It looks like that even under the worst conditions (with the highest level of benzene directly ingested into your body) the risk of cancer is still low compared to environmental exposure to this chemical. If you don’t find that reassuring enough then I see only one other option. Your only choice for true peace of mind is to avoid Vitamin C products that contain sodium or other benzoates. Fortunately this is easy enough to do by reading the ingredient list. (PS, yes, that’s Vitamin C Barbie in today’s picture.)