Fact Check

Did Pepsi 'Admit' Their Sodas Contain Cancer-Causing Ingredients?

Viral stories rehash a legal tussle between Pepsi and the Center for Environmental Health, but they mischaracterize that battle’s outcome.

Published Feb 26, 2018

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Pepsi admitted that their soda contains cancer-causing ingredients.

In 2016, the one-stop paranoia and supplement shop “Natural News” web site published an article, headlined “Pepsi Admits Its Soda Contains Cancer-Causing Ingredients,” that discussed a legal battle between the environmental health watchdog Center for Environmental Health (CEH) and PepsiCo which took place between 2011 and 2015. Clickbait websites have aggregated that story and ensured its continued virality by sharing it on highly followed Facebook accounts such as “March Against Monsanto.”

The 2016 Natural News article documented the Center for Environmental Health’s effort to uncover levels of a chemical called 4-Methylimidazole (4-MEI) in cola products that were higher than the legal limits imposed by the state of California's Proposition 65. 4-MEI is not directly added to colas, but it is a byproduct of processes that produce the caramel coloring that is typically added to such soft drinks: "4-methylimidazole (4-MEI) is a chemical compound that is not directly added to food; rather it is formed as a byproduct in some foods and beverages during the normal cooking process. [4-MEI] forms as a trace impurity during the manufacturing of certain types of caramel coloring ... that are used to color cola-type beverages and other foods."

To understand the legal challenge from the Center for Environmental Health and the claims made about this case by Natural News, though, one need first understand the regulatory history that culminated in efforts to reduce the chemical’s occurrence in soda.

Is 4-Methylimidazole a Carcinogen?

A number of international, national, and state or local governmental agencies evaluate the safety and possible carcinogenicity of various food or cosmetic products, and they don’t always reach the same conclusions. The first group that raised specific alarm about the carcinogenic potential of 4-MEI was the U.S. National Toxicology Program (NTP), which released a study in 2007 suggesting that massively high doses of 4-MEI may have given male and female mice lung cancer and may have given female rats Leukemia.

The state of California has some of the strictest laws in the world regarding required warnings about chemicals that may produce carcinogenic or reproductive harm. This situation is due to Proposition 65, also called the Safe Drinking Water and Toxic Enforcement Act, which since 1986 has mandated the publication of a list of chemicals that are “known to the State of California to cause cancer or reproductive toxicity” and imposed labeling requirements on any product sold in California that includes relevant concentrations of these chemicals.

When the 2007 National Toxicology Program study was published, the state of California was given their first legal rationale to include 4-MEI in the Proposition 65 list, because the National Toxicology Program is one of the organizations the act defines as a valid arbiter of carcinogenicity. In January 2011, after a period of review, 4-MEI was indeed added to California’s Proposition 65 list.

While the National Toxicology Program and the State of California consider 4-MEI a potential carcinogen, the U.S. Food and Drug Administration (FDA) and the European Food Safety Authority (EFSA) are far less concerned with it as a potential cancer risk in food products. In 2011, the EFSA re-evaluated 4-MEI and other byproducts of caramel color processing, finding that the levels Europeans were exposed to through food consumption were far lower than those that would raise any plausible carcinogenicity concerns.

Currently, the FDA’s position on 4-MEI is that the National Toxicology Program study showing harm in rodents had limited relevance to humans, because it was performed on laboratory animals exposed to levels of 4-MEI higher than any human would reasonably be exposed to: "Based on the available information, FDA has no reason to believe that there is any immediate or short-term danger presented by 4-MEI at the levels expected in food from the use of caramel coloring."

However, the State of California, basing their decision on numbers derived from those animal studies, ruled that any product containing levels of 4-MEI exceeding a certain concentration would have to be labeled as a potential carcinogen.

Did Pepsi “Admit” That Their Products Contain “Cancer-Causing Ingredients”?

After 4-MEI was added to the Proposition 65 list, the Center for Environmental Health sampled cola products from California for compliance with that regulation and found that a number of Pepsi and Coca-Cola products contained levels of 4-MEI exceeding the allowable limits established by California’s Proposition 65. The CEH filed a legal complaint on 23 February 2012, whereupon both Coca-Cola and Pepsi announced their intent to bring 4-MEI levels in the sodas into compliance with California law, as reported in a 9 March 2012 Reuters article:

Coca-Cola Co and PepsiCo Inc are making changes to the production of an ingredient in their namesake colas to avoid the need to label the packages with a cancer warning.

The change is meant to reduce the amount of a chemical called 4-methylimidazole, or [4-MEI], which in January was added to the list of chemicals covered by California’s Safe Drinking Water and Toxic Enforcement Act of 1986, also known as Proposition 65 ... Both companies said they started in California, and would expand the use of the reduced [4-MEI] caramel coloring over time.

Subsequent to this announcement, the CEH once again tested a variety of colas from California and elsewhere around the country, finding that both Pepsi and Coca-Cola were now compliant in California, but that Pepsi had not changed their soft drink formulations outside of that state. As a result, the CEH continued their legal efforts against PepsiCo.

On 17 September 2015, lawyers for PepsiCo and the CEH settled their dispute when they signed a consent judgement described thusly by the CEH:

Under the settlement, finalized in Superior Court in Alameda County, Pepsi will require its ingredient suppliers to meet strict limits on the 4-MEI levels, which CEH found at high levels in 2012 in some colas made by Pepsi and other major companies. The settlement also requires Pepsi to test its cola products to ensure that the 4-MEI levels remain below the required level, and allows CEH to request further testing of Pepsi’s products.

Although this agreement represented a major legal victory for the CEH (which was also awarded financial damages for their legal and scientific fees), it actually represented (legally, at least) the exact opposite of Pepsi's “admitting its soda contains cancer-causing ingredients” as stated in viral headlines. This is clear in the section of the judgement labeled “NO ADMISSIONS”, which stipulates that PepsiCo never violated any law and that they were not required to admit or accept 4-MEI’s classification as a carcinogen:

By executing this Consent Judgment and agreeing to provide the relief and remedies specified herein, [PepsiCo] does not admit (a) that it has violated, or threatened to violate Proposition 65 ... or any other law or legal duty; or (b) that the chemical 4-MEI in [their colas] or in other foods or beverages poses any risk to human health or requires any disclosure or warning to consumers.

The CEH was able to pressure PepsiCo into imposing strict guidelines on the manufacturing of the caramel color they use and to make a legal commitment to have 4-MEI levels in their soda regularly tested. They did not however, compel PepsiCo to admit, as claimed, that their sodas “contain cancer-causing ingredients.”


Z., Isabelle.   “Pepsi Admits Its Soda Contains Cancer-Causing Ingredients.”     Natural News.   15 September 2016.

U.S. Food and Drug Administration.   "Questions & Answers on Caramel Coloring and 4-MEI"     Accessed 26 February 2018.

National Toxicology Program.   "NTP Technical Report on the Toxicology and Carcinogenesis Studies of 4-Methylimidazole in F344/N Rats and B6C3F1 Mice."     January 2007.

American Cancer Society.   "Cancer Warning Labels Based on California’s Proposition 65."     Accessed 26 February 2018.

California Environmental Protection Agency.   "Chemical Meeting the Criteria for Listing as Causing Cancer Via the Authoritative Bodies Mechanism: 4-Methylimidazole."     March 2009.

California Environmental Protection Agency.   "No Significant Risk Level (NSRL) for the Proposition 65 Carcinogen 4-Methylimidazole."     October 2011.

EFSA ANS Panel.   “Scientific Opinion on the Re-Evaluation of Caramel Colours (E 150 a,b,c,d) as Food Additives.”     EFSA Journal.   8 March 2011.

Geller, Martinne.   “Coke, Pepsi Make Changes to Avoid Cancer Warning.”     Reuters.   9 March 2012.

Center for Environmental Health.   "One Year Later, Pepsi Still Contains Cancer-Causing Food Coloring."     3 July 2013.

Center for Environmental Health.   "Pepsi Agrees to Limit on Caramel Coloring Chemical in Colas."     17 September 2015.

Alex Kasprak is an investigative journalist and science writer reporting on scientific misinformation, online fraud, and financial crime.

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