The Center for Environmental Health revealed in the public on July 4 that Pepsi products still contain a cancer-causing chemical called 4-methylimidazole, or 4-MEI. This chemical was banned in Calif. since last year.

While the Pepsi sold in Calif. had been modified in compliance to the state provisions, those sold outside the state still have high amounts of 4-MEI. Coca-Cola has removed the chemical in their sodas and used a different substance instead to color there drinks.

Pepsi responded to the allegations and said that they were already working on modifying their manufacturing process by coordinating with their coloring suppliers. The soda maker promised that by 2014, all their products sold in the U.S will have a reduced amount of 4-MEI.

In a statement released on Friday afternoon as stated in Bloomberg, the company explained, “We strongly refute any claim that any product we sell anywhere is unsafe. The safety of our products is PepsiCo’s top priority, and we abide by the regulatory guidelines everywhere we do business. While we meet the strict FDA guidelines, when the regulatory requirements changed in California PepsiCo moved immediately to meet the new requirements and, in order to maintain a harmonized supply chain, globally committed to rolling out the changes across the rest of the U.S. and internationally.”

4-MEI is a chemical that produces the caramel coloring found in colas, soy sauces, beers, breads, and coffee. Last year, Calif. passed a state law called Proposition 65 requiring manufacturers to label any toxic substances present in their product. A study published in 2007 funded by the National Toxicology Program confirmed that constant exposure to 4-MEI may cause lung cancer based on an experiment conducted on female mice.

The U.S Food and Drug Administration did not immediately supported the provision because a person may need to drink a thousand cans of sodas a day in order reach the doses given to the female mice. The American Beverage Association also conducted their test and showed that 4-MEI was not a harmful substance. However, the FDA is reviewing whether this substance needs to be regulated.