The caramel coloring in your favorite soda is once again being scrutinized by the FDA. According to NBC News, the FDA is taking another look into the chemical 4-MeI, a carcinogenic byproduct produced in the manufacturing of caramel color, after a Consumer Reports test found higher than expected levels in sodas across the country.

Consumer Reports partnered with the Johns Hopkins Center for a Livable Future to test samples of various soda brands, including Pepsi, Coke, and Malta Goya, in California and New York for 4-MeI levels twice over the course of 2013. The study used a California measure to test the sodas: the state requires manufacturers to label any products that could expose consumers to more than 29 micrograms of 4-MeI per day, as that's the level the California Office of Environmental Health Hazard Assessment has determined to pose a one in 100,000 risk of cancer.

Pepsi delivered on its promise to lower 4-MeI levels in soda

The first test showed soda purchased in California had average levels around or below 29 micrograms per can, but the New York samples of the same brands reported much higher 4-MeI levels. However in the second test, soda samples from New York had reduced levels of 4-MeI — a can of Pepsi from the New York area averaged 174 micrograms in the first test and only 32 micrograms in the second. Overall, Coca-Cola came out on top, with its Coke, Diet Coke, and Coke Zero sodas coming in with under 5 micrograms each per can. Pepsi and Malta Goya had higher levels of 4-MeI in their sodas, but in the second test, Pepsi did bring that number down significantly as it promised to do in 2013. The same can't be said for Malta Goya — in both tests its 4-MeI levels were well above 300 micrograms, which is more than 10 times the acceptable limit.

The fact that the 4-MeI levels came down across the board is a sign of change, even if a small one. The evidence supporting the carcinogenic effects of 4-MeI date back to 2007, when the National Toxicology Program, a branch of the US Department of Health and Human Services, reported that the substance caused cancer in mice. And in 2011, the International Agency for Research on Cancer said the chemical could be "possibly carcinogenic to humans." Still there are no federal limits for the amount of 4-MeI in foods, but Consumer Reports is calling on the FDA to set one. The FDA continues to report that there is no reason to believe the compound is unsafe as used, but the agency will look into it further.