When the state of California added the compound 4-methylimidazole, also known as 4-MI or 4-MEI, to its list of known carcinogens in 2011, it created a problem for the soda industry.

The caramel color they used to give colas that distinctive, brown hue contained levels of 4-MI that would have warranted a cancer warning label on every can sold in the state.

And this wasn't the industry's only challenge. The Center for Science in the Public Interest petitioned the U.S. Food and Drug Administration to ban ammonia-sulfite caramel color. It's a request the CSPI repeated this week after finding 4-MI in samples of Coke and Pepsi.

"This is nothing more than CSPI scare tactics, and their claims are outrageous," writes the American Beverage Association in a statement released to the media.

"The science simply does not show that 4-MEI foods or beverages is a threat to human health," the statement continues.

And the FDA seems to agree.

FDA spokesman Douglas Karas wrote in a statement that the FDA is currently reviewing the CSPI petition, but "it is important to understand that a consumer would have to consume well over a thousand cans of soda a day to reach the doses administered in the studies that have shown links to cancer in rodents."

But in order to meet the requirements of California law — and avoid cancer warning labels on cans — soda manufacturers have come up with a solution: switch to a new, low 4-MI formulation of caramel coloring. Coca-Cola tells The Salt they've already begun the change.

"The company did make the decision to ask its caramel suppliers to make the necessary manufacturing process modifications to meet the requirement of the State of California," Diana Garza Ciarlante, a Coca-Cola spokeswoman, wrote in an email.

Garza Ciarlante says caramel coloring in all Coke products has always been safe.

"The fact is that the body of science about 4-MEI in foods or beverages does not support the erroneous allegations that CSPI would like the public to believe," she writes. Outside of California, no regulatory agency concerned with protecting the public's health has stated that 4-MI is a human carcinogen.

"Caramel color is now — and has always been — safe and harmless" says Ted Nixon, CEO of D.D. Williamson, the world's largest supplier of caramel color.

He explained that in order to modify the caramel color to reduce the levels of 4-MI, he sent his scientists back to the drawing board to change the manufacturing process.

"We did have to change these various inputs of temperature, pressure and the various ingredients we're using in order to change [4-MI concentrations]," Nixon says.

And Nixon says he'll be able to meet the demand of all of his soda clients, in rolling out this modified caramel color in products nationwide, and worldwide.

Coke says it will expand the use of the low-4-MI caramel color nationally, though Garza Ciarlante says it's important to note that the modifications will not change Coca-Cola products.

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