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Do Sodium Benzoate and Vitamin C react to form carcinogenic benzene?

Sodium Benzoate and Vitamin CAn intriguing query from an individual who calls themselves simply B.


I’ve been looking around online on topics related to Sodium Benzoate and Vitamin C as I have read that when these two ingredients are mixed it can form Benzene which is a known carcinogen. I’ve been looking for a good Vitamin C serum for a while now but most of the ones I encounter contain Sodium Benzoate.
What are your thoughts on this? Are the amounts of Vitamin C and Sodium Benzoate so small it would not react to create Benzene and if it was formed would it be harmful?
Thank you!

This is an interesting one.  The story about benzoic acid being converted into benzene was one that started in the soft drinks industry.  Benzoic acid has been used in soft drinks which also contain vitamin C, and benzene has been found in them. The reaction where benzoic acid is broken down into benzene is one that you find in the organic chemistry textbooks.  What the text books also reveal is the optimum conditions for the reaction to occur. These are a long way from what you find in soft drinks, and the levels of benzene found were extremely low. The trouble with molecules is they are very small and there are lots of them.  So even though the chances of forming benzene are low with billions of molecules around some of them manage to react even though the conditions for the reaction are not very favourable.  Even that doesn’t seem to be the whole story because when the UK’s FSA investigated they found that not all the drinks that theoretically could have contained benzene actually contained it.  So either there is another factor that is needed to promote the reaction that we haven’t identified yet, or the benzene was actually coming from some other source altogether.

In most cosmetic products the conditions would be even less favourable. And you don’t eat them.  So on the whole I don’t think there is much risk of benzene actually being created in cosmetic products, or of it doing any harm if it were.  It would be much less exposure than you probably get to benzene when you fill your car with petrol. So I think this is a non issue really, but I enjoyed getting my old chemistry book out.

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