As if we needed one, there’s yet another reason to avoid soda and soft drinks. Last week, Consumer Reports announced that it had found potentially carcinogenic levels of 4-methyllimidazole (4-MeI) in eight out of the 12 popular brands of soft drinks that it tested.

Caramel coloring is the most common coloring found in food and beverages such as beer, baked goods, and soft drinks. Of the four types of caramel coloring in use, only the two that are manufactured with ammonia compounds can contain 4-MeI. This chemical byproduct has been recognized as a possible human carcinogen by the International Agency for Research on Cancer and has been associated with the development of cancer in lab animals.

“There is no reason why consumers need to be exposed to this avoidable and unnecessary risk that can stem from coloring food and beverages brown,” stated Dr. Urvashi Rangan, a toxicologist and Executive Director of the Consumer Reports Food Safety and Sustainability Center.

Consumer Reports purchased and tested 81 containers of popular soft drink brands from five manufacturers in California and New York, from April to September 2013. An additional 29 samples of brands that had initially tested above 29 micrograms of 4-MeI per can or bottle were purchased and tested in December 2013.

The 12 brands tested were: Sprite, Diet Coke, Coke Zero, Coca-Cola, Dr. Pepper, 365 Everyday Value Dr. Snap, Brisk Ice Tea, A&W Root Beer, Pepsi, Diet Pepsi, Pepsi One, and Malta Goya.

During each round of testing, samples of Pepsi One and Malta Goya, purchased numerous times in both locations, exceeded 29 micrograms of 4-MeI per can or bottle. Malta Goya’s test results were particularly troublesome with levels regularly exceeding 300 micrograms of 4-MeI in a single container.

Although there are no federal limits on caramel coloring in food and drink, California’s Proposition 65 requires a warning label on any product that would expose consumers to more than 29 micrograms of 4-MeI in a day. In California, neither Pepsi One nor Malta Goya carried the warning label.

“We do not directly produce Goya Malta nor its ingredients and was unaware of the level of 4-MeI found in our products and the proper labeling required in the state of California based on Prop. 65. We rely on our suppliers to provide us with pertinent information and guidelines to make our products safe and of the highest quality,” Goya said via a written statement last week to Take Part.

“We are in the process of re-examining the ingredients used to produce Goya Malta, and our intent is to meet the standard requirements of our products and resolve the issue immediately,” continued the statement.

According to TakePart, a Goya representative asked for a retraction of the company’s statement the next day, asserting the Consumer Reports testing was inaccurate. The retraction was refused.

In a statement to the Los Angeles Times, PepsiCo Inc., which manufactures Pepsi One, a diet soft drink, says it is in the process of lowering the levels of caramel coloring in its products to meet California’s regulations. “All of our products are in full compliance with the law. When the regulatory requirements changed in California, PepsiCo moved immediately to meet the new requirements, and all of our products in California are below the California threshold,” PepsiCo told the paper.

However, PepsiCo’s assertion that it is currently meeting California Proposition 65 requirements may not be accurate. According to Consumer Reports, PepsiCo believes no warning label is required for Pepsi One, even when the amount of 4-MeI in a single can exceeds 29 micrograms, because Proposition 65 is based on per day exposure.

To calculate per day exposure, PepsiCo used the government’s National Health and Nutrition Examination Survey (NHANES) consumption data and concluded that average daily consumption of diet soda is less than a third of a 12-ounce can.

“We believe [Consumer Reports] conclusion is factually incorrect and reflects a serious misunderstanding of Prop 65’s requirements,” the company said to Take Part. “The highest amount of 4-MEI reported in Pepsi One equates to less than 14 mcg in the amount consumed per day by the average consumer.”

However, NHANES raw consumption data includes children, who are occasional soda drinkers, and consumers who drink it infrequently. NHANES averages them all into a single consumer consumption rate, which may not accurately reflect the habits of the average diet soda drinker.

While testing the 12 brands, Consumer Reports made a different assumption based on the NHANES data–that a consumer would drink a 12 ounce single serving of soda in one sitting.

Transcending the debate over daily consumption rates, Michael Jacobson, the Center for Science in the Public Interest’s (CSPI) Executive Director, wonders why there needs to be any caramel coloring in soft drinks at all.  “Government, industry, and academic scientists agree that if a chemical causes cancer in animals it should be presumed to cause cancer in humans, as well,” said Jacobson. “It’s a purely cosmetic ingredient. The world would not end if soda companies simply stopped using it.”

Based on its test results, Consumer Reports has petitioned the U.S. Food and Drug Administration (FDA) to create a federal standard for 4-MeI in food and drink.  It also has asked the FDA to immediately require manufacturers to list the type of caramel coloring they use on their ingredient lists so consumers can make an informed choice.

Consumer Reports also said it notified the California state attorney general about samples purchased in California that, on average, exceeded 29 micrograms of 4-MeI, so an investigation could be initiated to see whether Proposition 65 was violated.

This is not the first time that worrisome levels of 4-MeI in soft drinks have been brought to the attention of the FDA. In 2012, CSPI sent a letter to the FDA Commissioner requesting her to take action after estimating that the amount of 4-MeI found in Coke and Pepsi products they tested could be responsible for approximately 15,000 cancers yearly in the U.S. Shortly after CSPI’s test results were made public, Coca Cola switched to a low-4MeI formula, which is reflected in the new testing data compiled by Consumer Reports.

According to the Daily Mail, Coca-Cola subsequently promised to reduce levels of 4-MeI in drinks sold around the world. However, Pepsi did not make a similar promise, which outraged food reformers in the United Kingdom.

Some of the other findings from Consumer Reports’ testing included:

• Only one product tested, Sprite, which was tested as a control because it is clear and doesn’t use caramel color, had no significant level of 4-MeI.
• 4-MeI levels varied widely between the coasts, in some brands. For example, in New York, 12 ounces of Diet Pepsi was found to have an average 4-MeI level of 182.7 micrograms in the first round of testing, while the average level in California was 30.5 micrograms.
• In the second round of testing in New York, average 4-MeI levels in two brands, dropped dramatically–Pepsi from 174.4 to 32.4 and Diet Pepsi from 182.7 to 33.5–indicating that Pepsi may be working to cut 4-MeI levels permanently.
• Coca-Cola products that were tested had the lowest levels of 4-MeI. On average, Coke, Diet Coke, and Coke Zero tested under 5 micrograms per can.
• Whole Foods’ Dr. Snap brand has a “natural” label, but was found to contain 4-MeI, which is artificial.

Jacobson pointed out that there has been major progress over the past three years in reducing 4-MeI in soft drinks, but that the FDA needs to act to bring levels down further. “The FDA should test a wide variety of products, including ones aimed at ethnic populations,” said Jacobson.

The FDA continues to maintain that there is no immediate or short-term danger presented by 4-MeI. However, in response to the Consumer Reports testing, the FDA said in a statement that it would be reviewing “all available data on the safety of 4-methylimidazole (4-MeI)” and that it “has no reason to believe that 4-MeI, at the levels expected in food from the use of caramel colors, poses a health risk to consumers.”