Two types of caramel coloring used in some sodas and foods contain two carcinogens and should be banned, according to the nonprofit Center for Science in the Public Interest (CSPI). The caramel coloring used in some sodas is manufactured via a chemical reaction between sugars, ammonia, and sulfates. These reactions produce the two carcinogens: 2-methylimidazole (2-MEI) and 4-methylimidazole (4-MEI), he says. These chemicals have been shown to cause cancer in mice and rats. Representatives from the beverage industry and from the Coca-Cola Company reject the claims that the additives are dangerous, and Coca-Cola notes in a statement that 4-MEI "forms normally in the ‘browning reaction’ while cooking, even in one’s own kitchen." Jacobson says that 2-MEI and 4-MEI "are not potent carcinogens, but it is totally inappropriate to accept any risk from artificial coloring that has no nutritional or preservative value." Natural alternatives -- including dark colorings from beets or carrots -- do exist, he says. Alternatively, the soda industry could market clear colas. The FDA will now review the petition.