Pepsi-Cola is still using a caramel coloring containing a chemical linked to cancer in rodents more than a year after publically pledging to eliminate it, according to the environmental watchdog group Center for Environmental Health (CEH).

Last March, both Coca Cola and PepsiCo stated they would change their caramel coloring products nationwide as a result of a California law, called Proposition 65, requiring labels on products with 4-methylimidazole, or 4-MeI.

According to CEH, independent testing shows that Coke has largely reformulated while the chemical was found in all 10 Pepsi products from outside California.

Specifically, lab tests found little or no 4-MeI in nine out of 10 Coke products, but showed high levels of 4-MeI in all 10 Pepsi products. All told, the tests show that outside of California, Pepsi contains four to more than eight times more of the chemical than is currently allowed in California.

"This shows how California's Proposition 65 law can make products safer for all Californians, and in some cases for all Americans," Michael Green, executive director of CEH, said in a press release. "We applaud Coke for taking this health protective action for consumers nationwide. Pepsi's delay is inexplicable. We urge the company to take swift action to provide all Americans with the same safer product they're selling in California."

Industrial production of caramel coloring creates 4-MeI as a by-product, but processing changes can reduce or eliminate production of the chemical without altering the coloring, according to CEH.

According to Fox News, Pepsi said its caramel coloring suppliers are currently changing these manufacturing prcoesses in order to cut the amount of 4-MeI in its caramel and that while that process has been completed for California products, this will not be the case for the rest of the country until Feb. 2014.

California added 4-MeI to the state list of chemicals known to cause cancer after the National Toxicology Program found evidence of carcinogenicity of the chemical in animal studies back in 2007. However, the Food and Drug Administration has said that a consumer would ahve to drink more than 1,000 cans of soda a day to reach the doses adminstered in rodents that went on to develop cancer.