Feb 14 2014

Eating Yoga Mats

This is the worst example of pseudoscientific fearmongering I have seen in a while, and that’s saying something.

Vani Hari, a blogger known as “food babe,” has started a petition to get Subway to remove use of the chemical azodicarbonamide from their breads. She writes:

Azodicarbonamide is the same chemical used to make yoga mats, shoe soles, and other rubbery objects. It’s not supposed to be food or even eaten for that matter. And it’s definitely not “fresh”.

This, of course, is utter nonsense – that is, the notion that because a chemical has multiple uses, included in non-food items, that it is not “supposed” to be eaten. Azodicarbonamide (ADA) is used as a blowing agent in the formation of certain rubbers and sealants. It is used, for example, in sealing the tops of baby food containers, but also in the production of certain plastics and rubbers. It is also used as a bleaching agent for bread, giving it a softer and fluffier quality. None of this says anything about it’s safety at the levels used.

Hari then gives us a scary list of items that suggest ADA is dangerous. It reminds me of the “dihydrogen monoxide” parody. It shows that pseudoscience is often self-parody. She goes on:

  • The World Health Organization (1) has linked it to respiratory issues, allergies and asthma.
  • The U.K. Health And Safety Executive has recognized azodicarbonamide as a potential cause of asthma. (4)

 Here is what the WHO actually says:

“Case reports and epidemiological studies in humans have produced abundant evidence that azodicarbonamide can induce asthma, other respiratory symptoms, and skin sensitization in exposed workers. “

In exposed workers – people working in factories where ADA is used as a blowing agents and who therefore might get direct exposure to the aerosolized chemical. This has absolutely no relevance for the risks of its use in making bread. The referenced UK health report states:

Evidence that azodicarbonamide can induce asthma in humans has been found from bronchial challenge studies with symptomatic individuals and from health evaluations of employees at workplaces where azodicarbonamide is manufactured or used.

So if you have asthma, don’t breath it in. She continues:

  • When a truck carrying azodicarbonamide overturned on a Chicago highway in 2001, it prompted city officials to issue the highest hazardous materials alert and evacuate people within a half mile radius! Many of the people on the scene complained of burning eyes and skin irritation as a result. (3)

Again – exposure to large amounts of the pure chemical is not the same as being exposed to tiny amounts in food. The same caution would be appropriate for a spill of any concentrated pure chemical found in food.

  • When azodicarbonamide is heated, there are studies that show it is linked to tumor development and cancer. (5)

She is referring to a breakdown product, semicarbazide (SEM). Here is a review of the safety of this chemical from ADA use in baby food jars:

SEM shows limited genotoxicity in vitro that is largely prevented by the presence of mammalian metabolic enzymes. Negative results were found in vivo in DNA alkaline elution, unscheduled DNA synthesis and micronucleus assays. This pattern is in contrast to the genotoxic hydrazines that also have been shown to cause tumours. Carcinogenicity studies of SEM are of limited quality, show a questionable weak effect in mice at high doses, which are not relevant to human exposure at trace levels, and show no effect in the rat. The IARC has assigned SEM as Group 3, ‘Not classifiable as to its carcinogenicity to humans’. Based on estimates of exposure to infants consuming baby foods (with the assumption of SEM levels at the 95th percentile of 20 ng g(-1) in all of the consumed ‘ready-to-eat’ foods) compared with a no observed adverse effect level (NOAEL) in developmental toxicity studies, the margin of safety is more than 21 000.

An apparently more responsble food blog, Food Insight, also notes:

As of Feb. 10, 2014, SEM is listed by the International Agency for Research on Cancer as “not classifiable as to its carcinogenicity to humans.” SEM does not appear on California’s Proposition 65 list of “Chemicals Known to the State to Cause Cancer or Reproductive Toxicity.” The National Toxicology Program’s “12th Report on Carcinogens” does not list SEM either as a “Known Human Carcinogen” or a “Reasonably Anticipated Human Carcinogen.”

The evidence shows that ADA and SEM, at the levels consumed in food, are negligible and pose no human health risk.

But, Hari adds:

  • Not only is this ingredient banned in Europe and Australia, but you also get fined 450,000 dollars if you get caught using it in Singapore and can serve 15 years in prison (2).

If you read her own references, specifically the UK report, you will find:

On the basis that azodicarbonamide is a human asthmagen and that the concentrations required to induce asthma in a non-sensitive individual or to provoke a response in a sensitive individual are unknown, it is concluded that there is a risk to human health under present occupational exposure conditions. The level of risk is uncertain; hence, exposure levels should be reduced as much as possible.

In other words – ADA is banned because of the risk of exposed workers directly to the pure gas, not based on any risk in food.


Hari the food babe has created a classic piece of pseudoscientific scaremongering, worthy of dihydrogen monoxide. She has collected a group of factoids that superficially appear scary, but do not relate to the risk of ADA as used in bread. They are designed to mislead and to stoke fears based upon scientific misunderstanding.

She also pulls the common scam of linking to references to support her claims, but not fairly representing what those references actually say.

Unfortunately, it appears that Subway is caving to this petition. I can’t blame them. It’s easy to fearmonger, especially about food, and more difficult to reassure customers with sober scientific facts. They have to think of their business bottom line.

But this essentially means that any blogger can hold any corporation hostage by simply grossly misrepresenting the scientific facts. It is unfortunate – it’s similar to caving into terrorism. I would hope, rather, that the food babe would be exposed for what she is, and that corporations would fight back against these nonsensical attacks.

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