Benzene Soda

Sodium benzoate (E211) is a public health issue that has been bubbling for fifteen years and could soon come to a head and have the fizzy drinks industry frothing at the mouth.

Sodium benzoate is a preservative added to carbonated beverages, but those drinks that also have added citric or ascorbic acid (vitamin C, E300) can be susceptible to the formation of benzene as a degradation product. At least that’s the theory.

The US Food & Drugs Administration (FDA) was aware of this issue in the 1990s and alerted manufacturers who were then meant to introduce a “quick fix” to prevent this carcinogenic degradant from forming in amounts above safety levels. However, there have been hundreds of new susceptible beverages brought to market the world over since by smaller manufacturers as well as the well-known ones and seemingly the benzene message has been lost in the intervening time.

Germany’s food watchdog, BfR, and the UK’s Food Standards Agency are currently testing drinks to see whether benzene levels are above WHO recommendations. Other countries are also on the alert. The renewed concern follows the FDA’s re-opening of an investigation, closed for 15 years, into benzene in soft drinks.

You can read more details of this at industry newsletter Beverage Daily

Some studies have shown that levels of benzene are present at five times the WHO’s limit for drinking water contamination and can occur in bottled soft drinks exposed to heat and light especially.

In acid conditions, benzoate is converted to benzoic acid (the active antimicrobial form, benzoate is added as a preservative for a reason after all) and it is thought that it interacts with hydroxyl radicals released by the ascorbic acid (better known as vitamin C) reaction with iron or copper ions in the water. These hydroxyl can decarboxylate benzoic acid, releasing carbon dioxide and leaving benzene behind. But, at what rates this occurs is not clear.

Moreover, leaving out the ascorbic or citric acid from soft drinks would be the simple solution and avoiding benzoate as a preservative in foods that contain these acids naturally would offer an end to the “problem”.

However, the issue brings to the fore once again the issue of acceptable risk. Sodium benzoate is present in soft drinks only in very small amounts and even if degradation were complete, the risk to someone drinking it is tiny. To have the same exposure as lab animals used to demonstrate carcinogenicity would mean a person having to drink 10,000 bottles of benzoate-containing soda.

Still, such minor details will not stop the media from jumping on this as the next big scare story despite the fact that it’s been around for years as public chemophobia.

22 thoughts on “Benzene Soda”

  1. Well Jonathan, I’m sure my response to another reader did not come up to your exacting standards. I thought I answered her quite well, to be honest. Anyway, I’m running a blog here, not a homework help service. It’s not a straightforward matter to test for benzene, it’s an organic molecule, not a simple metal ion, for instance, you need specialist equipment. If there’s a local lab that is interested in helping out students then you may have some success in persuading them to do the tests for you, but how would that be *your* science fair project?

  2. I’m hoping for a better answer than the one you gave Amanda in November 2006. I am wanting to do a science fair project on the levels of benzene in sodas exposed to heat which contain acsorbic acid and sodium benzoate. My school has said if I can find a way to test for benzene, they will approve it. Please let me know of ways that I can test it myself, or places that I can send samples to for testing.

  3. It’s odd, this post got a lot of interest at the time of writing (February 2006) but has suddenly received renewed interest in May 2008, having been read more than 3200 times already (it’s May 13 right now). As far as I am aware there have been no significant developments on this, but am willing to stand corrected if any new research has come to light that I have overlooked. If you know of any, feel free to comment and bring us up to date.



  4. Dear Sciencebase or other guys/gals-

    Have a newborn with bad colic. Do not wish to expose to Benzene via Mylicon Drops. Researching issue of Citric acid vs Ascorbic acid as converting agent. Your comments re Citric not a converter are of great relevence to me as the Baby product uses Citric, not Ascorbic.

    Science base was to follow up on issue. Would you please update STAT! Anybody else? I prerfer her to get her benzene via our great Houston airand not in the Formula! Adopted baby .Breast feeding not possible so bottle colic has arrived. Seriously any help stat would be great. These drops work so hopefully there has been some reseach establishing a distinction in Citric v Ascorbic. HELP. Need sleep. Thanks

  5. Anonymous, I have absolutely no idea what point you are trying to make. Your original reference to chocolate and cocaine is bizarre, no one was under the illusion that cocoa and coca are the same! I removed your offensive reference to the causes of blindness. But, I would like to understand what pertinence this item has to the truly worrying trend for drinking gallons of carbonated acidic beverages. I’m not at all worried about trace amounts of benzene in these drinks, it is the relatively vast quantities of sugar, the phosphoric or carbonic acid content and the effect long-term consumption could have on teeth, obesity, and bone density that concerns me.

  6. Remember when mom said don’t eat dirt – the latest on that was it develops a stronger immune system so it is ok, no harm in eating dirt. Coffee will stunt growth, not so said scientists. Eating or drinking chocolate is as addictive as cocaine…

  7. Well, it’s not the testing for it that would be too dangerous. If you have a sample containing benzene, then it represents an intrinsic risk factor regardless of whether you’re testing it or not, but that risk depends on actual dose.

    I’d recommend finding an alternative science fair project:

    Of course, you must consider dose and possible routes of exposure when discussing any sample as to whether it’s dangerous or not. Benzene is an aromatic hydrocarbon occurring naturally in crude oil and many other substances and is present in petrol (gas) because of this and because it is formed during oil refining. The quantities in soda and other fizzy drinks mentioned in this post are tiny compared to the levels in petrol.

    As such, you’re going to struggle to do a science fair project to determine benzene in soda, without proper analytical lab equipment. On the other hand, you would be wise not to take a sample of petroleum into class to test even though the levels of benzene might be more accessible. Regardless of the long-term risks of cancer from exposure to benzene, it smells strongly, is poisonous, and flammable. Steer clear.

  8. I need to do a science fair project and I’m looking for a procedure for testing benzene levels. Is there some place I should look to find it? or is it something that is extremely dangerous and expensive to test for?

  9. Sophia, thank you for pointing that out. That’s my concern too. The drink you mentioned is very very popular among ppl from HK. It’s such a great homeotherapy (I think) to suppress the growth of a cold!

    Thanks to Sciencebase for the prompt reply that definitely relieves my worry! :)

  10. No. There is only a tiny, tiny amount of benzoate added to any drink or food product in the first place. This stuff is expensive, manufacturers add the bare minimum to give the effect they’re after. Even if the amount of benzene in a drink exceeds the WHO drinking water limit by a factor of ten, you’d still have to somehow drink several thousand sodas to ingest a toxic quantity and even then it would not be a single dose, so very unlikely to have any harmful effects at all.

  11. Just for your information, in Hong Kong there is a special drink, made by boiling cola with slices of lemon and ginger. It is a lay method for treating colds. So, would this drink contain relatively higher level of benzene because it was mentioned that heat can speed up the reaction between vitamin C and sodium benzoate?

  12. What an amazingly anarchistic comment! I don’t think.

    It does raise an interesting point, however. Had you ingested enough benzene to “taste” it, it is rather unlikely you would want to brag about the experience, the hospital visit, the putative liver damage, the brooding cancer cells. The presence of the tiny quantities of benzene thought to potentially form in sodas is just so small that the taste is simply not detectable within the milieu of other ingredients, particularly the drink’s flavourings. In fact, even at the height of the benzene in bottled water fiasco of the late 1980s/early 1990s no one could honestly say they could taste the benzene in those curvy green bottles.

    Moreover, your posting inspires another thought. A blog comment can last forever, not just for high school, so it is just as well you kept yourself semi-anonymous, as employers often Google job applicants these days. I suspect having read your comment here, most employers would be inclined to fold your resume sheet neatly into a paper plane and launched it into the office wastepaper basket. N’est ce pas?

    Hey, why not submit a humorous and detailed riposte to my response, but this time post your full name and address. You never know they might be looking for comedy script writers.

  13. Threshold limits … from ‘Probability Theory: The Logic of Science’ by E T Jaynes (the book was once in the public domain). Preface xxv – xxvi

    “A common error, when judging the effects of radioactivity or the toxicity of some susbtance, is to assume a linear response model without threshold (ie without a dose rate below which there is no ill effect). Presumably there is no threshold effect for cumulative poisons like heavy metal ions (mercury, lead), which are eliminated only very slowly, if at all. But for virtually every organic substance (such as saccharin or cyclamates), the existence of a finite metabolic rate means that there must exist a finite threshold dose rate, below which the substance is decomposed, eliminated, or chemically altered so rapidly that it causes no ill effects. If this were not true, the human race could never have survived to the present time, in view of all the things we have been eating.

    Indeed, every mouthful of food you and I have ever taken contained many billions of kinds of complex molecules whose structure and physiological effects have never been determined – and many millions of which would be toxic or fatal in large doses. We cannot doubt that we are daily ingesting thousands of substances that are far more dangerous than saccharin [or benzene?] – but in amounts that are safe, because they are far below the various thresholds of toxicity. At present, there are hardly any substance, except some common drugs, for which we actually know the threshold.”

    Are the safety limits of benzene based upon threshold limits? And, how does this vary among populations?

  14. I realise citric and ascorbic acid are different compounds (ascorbic acid being more familiar a vitamin C, the antiscurvy, a-scorbic factor). You may be right on the point about citric acid not releasing hydroxyl radicals. I will double check.

  15. As a point of clarification, citric acid and ascorbic acid are different compounds. It appears as though only ascorbic acid (vitamin C) produces the hydroxyl radicals that can decarboxylate benzoic acid, forming benzene. As far as I can tell, drinks containing citric acid and sodium or potassium benzoate have not been shown to produce benzene.

  16. Excellent article regarding Benzene in soda. While drinking 10000 sodas might be pretty extreme for us to imagine, there are lots of other sources of benzene. Just recentally there have been a number of studies that have found benzene contamination from utility plants in Indiana, as well as a plume of 50,000 gallons of gasoline in Pennsylvania. As a result I have posted more information in regards to the benzene and soda story here: and more regarding the gasoline spill in Pennsylvania:

  17. Note that WH0 standard for drinking water is 10 ppb.

    The EPA standard for drinkingw after is 5 ppb.

    The EU standard is now 1 ppb (though once was 10 ppb).

    The global recall of Perrier occurred when it tested in the 11-18 ppb range.

    Coca-Cola soft drinks recalled in France and Belgium in 1999 after benzene was found at comparable levels.

    In Belgium the benzene was due to contaminated carbon dioxide, which is a separate issue.

    In 1998, there was a massive recall in Great Britain due to benzene contamination, again thought due to contaminated carbon dioxide.

    It is primarily a matter of quality assurance and candor with consumers. If a product contains benzene, it should be disclosed to consumers so that they can make an informed beverage choice.

    The retailers polled in the 1990s felt there should be a recall whenever the level for drinking water was exceeded because that it is what consumers would expect.

    The cancer risk is long term — but many consumers might prefer to drink a beverage that does not contain benzene in it. There is no need to use the ingredients that lead to the benzene — the companies use the sodium benzoate in order to “cold-fill” the products, which is cheaper for them.

    I’ve uploaded the FDA and internal documents at

    The effect is greatest upon exposure to heat and light.

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