Despite California's strict laws requiring that foods containing cancer-causing chemicals be labeled with warnings, a new investigation from Consumer Reports has discovered worrisome levels of a potential carcinogen in Pepsi One and other sodas.

The independent nonprofit consumer safety group tested 110 samples of the sweet, bubbly drinks purchased at various stores between April and September 2013 and found that several surpassed what California has deemed a safe threshold.

In 2011, when California added a caramel coloring known as 4-methylimidazole (4-MEI) to its known-carcinogen list (and a court upheld the state’s right to do so), many soda companies scrambled to ensure their products complied with the state law establishing a daily limit of 29 micrograms. By law, products with more of the carcinogen must carry a label warning consumers.

A Pepsi One sample purchased in Ventura, Calif., in July came in at 49 micrograms, the investigation found. Ten other Pepsi One samples from California stores tested above the state’s threshold.

In a statement, PepsiCo accused Consumer Reports of being wrong about its measures of per-day consumption.

“We believe their conclusion is factually incorrect and reflects a serious misunderstanding of Prop 65’s requirements,” read the company statement. “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.”

“Per day” is the key phrase there. Pepsi takes the federal government’s National Health and Nutrition Examination Survey—which provides raw data on a variety of consumption habits across a wide demographic, including children who may drink soda occasionally and consumers who drink it infrequently—and averages them all into the overall consumption rate.

Consumer Reports' testing assumes that in a typical sitting, an individual drinks one 12 oz. can, or 1 serving, as the nutrition label says. Pepsi prefers to go by the survey's national average.

"Based on NHANES data, the average amount of diet soda consumed by those who drink it is approximately 100 ml per day, or less than a third of a 12 oz can," wrote Pepsi spokesperson Aurora Gonzalez in an email.

By that calculation, a typical diet soda drinker may only have one can over the course of a few days, and therefore, Pepsi believes it is in compliance with California law.

PepsiCo adds that it has voluntarily applied the same standards to the rest of the country. Indeed, Consumer Reports samples show that for some Pepsi products, the levels of 4-MEI declined over the testing period. Samples of regular Pepsi purchased in the New York area averaged 174 micrograms during the first round of testing in April; the average dipped to 32 micrograms by July.

Though it may be the most well recognized, Pepsi didn't have the beverage with the highest numbers of the additive. In two samples of Malta Goya , levels detected were 13 times California's threshold, with 392 micrograms per serving.

Related "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," said Goya in a written statement issued Wednesday afternoon.

According to Goya, caramel colors, including 4-MEI, are listed as Generally Regarded as Safe by the FDA—a claim Consumer Reports refutes.

"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.

On Thursday morning, a Goya representative contacted TakePart to ask for a retraction of the company's statement, saying the Consumer Reports official report was inaccurate. TakePart declined.

While the Pepsi One and Malta Goya numbers were above the California per-day guideline, the companies aren't required to reformulate if they want to keep selling the same soda—they just need to label the products to comply with state law. There are no federal limits on the caramel coloring, despite a two-year government study done by the National Toxicology Program that found it to be carcinogenic. The beverage industry says the color additive is safe.

On Tuesday, Consumer Reports asked the California Attorney General’s Office to further investigate. State prosecutors did not respond to interview requests.

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Consumer Reports says the study isn’t large enough for it to recommend one brand over another—but it was clear that Coca-Cola products fared far better than its cola rival's in the data the study did gather. Coke, Diet Coke, and Coke Zero consistently came in under five micrograms, whether they were purchased inside or outside California.

The FDA told TakePart that it appreciated the work done by Consumer Reports and said it was testing a variety of foods for 4-MEI, including sodas, and reviewing new safety data on the chemical.

“Currently, the FDA 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,” said FDA spokesperson Juli S. Putnam.

But Dr. Urvashi Rangan, a toxicologist and executive director of Consumer Reports' Food Safety and Sustainability Center, warned of serious risk.

"One serving will put you at an increased risk level. This is being manufactured into products, so there’s something we can do about it,” Rangan said.

It’s important to differentiate between caramel the coloring and caramel the flavoring, Rangan added, because the soda industry says the color additive is a Generally Regarded as Safe ingredient. Rangan says not so fast: The GRAS listing is for caramel flavoring—not caramel color.

“What we’re looking at is caramel color—a lot of people are confused by that. The color makers link to it. The American Beverage Association says it’s GRAS. All of that is not correct. No color additives are considered GRAS. That is an FDA policy,” said Rangan.

Consumer Reports believes the issue is so important that it is calling on the FDA to set standards, and for the coloring to be eliminated from so-called natural sodas such as Whole Foods’ Dr. Snap.

“What is an artificial color doing in a product that’s labeled natural? We’re asking the FDA to disallow that,” said Rangan. “This isn’t limited to colas. Soups, broths, soy sauces, coffee drinks, pumpernickel bread, all have caramel coloring. The fact is, the International Agency for Research on Cancer classified 4-MEI as a possible human carcinogen."

Which is why the investigative group is also calling on the FDA to improve ingredient labeling. Not all caramel coloring is controversial. There are four types of caramel coloring, but ingredient panels on products don’t differentiate among them. A listing of “caramel color” or “artificial ingredients” means consumers are unable to determine whether the product they’re consuming contains the controversial 4-MEI or another class of caramel coloring.

“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,” said Rangan.