BenzeneA recent ruling by a Nigerian high court judge has sparked a round of online discussion about the safety of certain soft drinks. The ruling actually only affects the Nigerian Bottling Company (NBC) and their manufacturing of certain Coca-Cola products, Fanta and Sprite. Before I get to the court case, here is the background science.

Benzene in soft drinks

Benzene is a known carcinogen. Long term exposure increases the risk of certain cancers, such as leukemia and myeloma. It is therefore the goal of regulatory and health agencies to minimize human exposure to benzene to levels that carry an insignificant risk.

The World Health Organization reports:

Because of the unequivocal evidence of the carcinogenicity of benzene in humans and laboratory animals and its documented chromosomal effects, quantitative risk extrapolation was used to estimate lifetime cancer risks. Based on a risk estimate using data on leukaemia from epidemiological studies involving inhalation exposure, it was calculated that a drinking water concentration of 1 µg/litre was associated with an excess lifetime cancer risk of 10-6 (10 µg/litre is associated with an excess lifetime risk of 10-5 and 100 µg/litre with an excess lifetime risk of 10-4) (15).

A “µg/litre” is a microgram per liter, which is equal to one part per billion (ppb). So regular exposure to benzene in 1 ppb had an increased lifetime risk of cancer of 10-6, which is one addition case per million people.

We are exposed to benzene in gasoline fumes, tobacco smoke, fumes from other products that contain benzene, and a small amount gets into our food and water. Smokers have 3-6 times the exposure to benzene than non-smokers. The WHO also reports that the amount from drinking water is a small overall contribution:

Exposure to benzene may vary considerably. For nonsmokers, the estimated average daily intake is 200–450 µg/day. The estimated contribution from food is 180 µg/day but, as information on benzene levels in food is very scanty, this background level should be considered only as an approximate reference point. For smokers, the intake levels are increased by a factor of 2–3 (urban areas) or 2–6 (rural areas). The levels commonly found in drinking-water are minimal compared with the intake from food and air (3).

Benzene is not directly added to soft drinks, although there may be a tiny amount from the water used to manufacture the drinks. However, benzene can form from a combination of benzoic acid, which is added as a preservative, and ascorbic acid (vitamin C). This reaction is increased by heat and light and inhibited by sugar and EDTA.
So, how much benzene gets into soft drinks and how much is allowed? The various regulatory agencies around the world limit benzene from 1 to 10 ppb. At one ppb, if you drank one liter of the soft drink you would consume 1 microgram of benzene. In one review of 28 soft drink products the mean benzene levels detected were 0.45 ppb. In that survey two citrus fruit-based drinks (so they contained benzoic acid and ascorbic acid) exceeded 1ppb.
Another survey of 199 soft drinks found:

The vast majority of beverages sampled contained either no detectable benzene or levels below the U.S. Environmental Protection Agency’s drinking water limit of 5 ng/g. Beverages found to contain 5 ng/g benzene or more were reformulated by the manufacturers. The amount of benzene found in the reformulated beverages ranged from none detected to 1.1 ng/g. [1 ng/g is also equal to 1 ppb – SN]

Soft drinks therefore have a very low level of benzene, with the vast majority being lower than the legal limit, but a few having just above the more stringent limits. Now, let’s put this level of exposure into context. Again, 1 ppb would give you one microgram from a liter of soft drink. Let’s use a high estimate of 5 micrograms per day from soft drinks, assuming someone drinks 5 liters a day of a soft drink at the limit of 1ppb.

The WHO, as stated above, estimates that the average person is exposed to 250-400 micrograms of benzene per day. You will inhale 32 micrograms when you fill up your car, and 40 micrograms from driving for one hour. Smokers inhale 2-7 thousand micrograms a day, and passive exposure to smoke contributes an estimated 50 micrograms per day.

Total contribution from food and water is estimated at between 1 and 3 micrograms per day, which is a small contribution to overall exposure.

The Nigerian case

The recent court case decision (the case itself was filed 10 years ago and took this long to get a decision) dealt with a lawsuit from an exporter. They attempted to export Fanta and Sprite bottled in Nigeria by the NBC to the UK. The product was tested on import into the UK and found to exceed their limit on benzoic acid (note – this refers to benzoic acid, not benzene):

The UK standards limit benzoic acid in soft drinks to a maximum of 150 mg/kg. Both Fanta and Sprite have benzoic levels of 200 mg/kg which is lower than the Nigerian regulatory limit of 250 mg/kg when combined with ascorbic acid and 300 mg/kg without ascorbic acid and also lower than the 600 mg/kg international limit set by Codex.

So the product was compliant with Nigerian and international limits, but over the stricter limit for the UK. The case focused on whether or not the NBC and the Nigerian regulatory agency (National Agency For Food and Drug Administration and Control – NAFDAC) was negligent in allowing these higher limits. NBC claimed that they bottle soft drinks for local distribution and comply with local regulations, and their product is not intended to export. The judge, apparently, did not buy this argument:

In her judgment, Justice Oyebanji said: “It is imperative to state that the knowledge of the Nigeria Bottling Company that the products were to be exported is immaterial to its being fit for human consumption. The court is in absolute agreement with the learned counsel for the claimants that soft drinks manufactured by Nigeria bottling company ought to be fit for human consumption irrespective of color or creed.

“It is manifest that NAFDAC has been grossly irresponsible in its regulatory duties to the consumers of Fanta and Sprite manufactured by Nigeria Bottling Company. In my respective view, NAFDAC has failed the citizens of this great nation by its certification as satisfactory for human consumption products, which in the United Kingdom failed sample test for human consumption, and which become poisonous in the presence of Ascorbic Acid ordinarily known as Vitamin C, which can be freely taken by the unsuspecting public with the company’s Fanta or Sprite.”

I’m no legal scholar, but that seems like a massive overreaction to me. It sounds like the judge had a political point to make. They are claiming that these products are poisonous and not fit for human consumption because they contain 200 mg/kg of benzoic acid, when the international limit is 600 mg/kg, but the UK’s limit is 150. Further, all the evidence suggests that even at the higher limit the amount of resulting benzene would be well below safety limits and an insignificant contribution to overall benzene exposure.

As always, the dose makes the poison. And, when considering overall exposure, individual sources should be put into the proper context of how much they contribute. Benzoic acid and resulting benzene from soft drinks is a non-issue. Overall the levels are extremely low, and are a minor contributor to overall benzene exposure. The Nigerian court decision has more to do with political maneuvering than the actual science.

Posted by Steven Novella

Founder and currently Executive Editor of Science-Based Medicine Steven Novella, MD is an academic clinical neurologist at the Yale University School of Medicine. He is also the president and co-founder of the New England Skeptical Society, the host and producer of the popular weekly science podcast, The Skeptics’ Guide to the Universe, and the author of the NeuroLogicaBlog, a daily blog that covers news and issues in neuroscience, but also general science, scientific skepticism, philosophy of science, critical thinking, and the intersection of science with the media and society. Dr. Novella also contributes every Sunday to The Rogues Gallery, the official blog of the SGU.