Coca-Cola and PepsiCo are making changes to the formulas of caramel colour used in sodas in order to avoid a cancer warning label in compliance with a California law.
The companies have already implemented the changes in drinks sold in California and will expand the alterations across the US to streamline their manufacturing processes.
The additive being lowered is a compound called 4-methylimidazole (4-MI or 4-MEI).
California recently added 4-MI to its list of carcinogens, after high levels of the compound were linked to tumours in rodents, even though studies did not show a similar effect in humans.
The American Beverage Association, a US trade organisation that represents the beverage industry, said that its member companies will continue to use the caramel colouring, but changes were made to comply with California's new regulation.
Coca-Cola and PepsiCo represent almost 90% of the soda market, according to non-alcoholic beverage industry tracker Beverage Digest.
Coca-Cola representative Diana Garza-Ciarlante told the Associated Press news agency that the company has asked its suppliers of caramel colouring to change the manufacturing process to lower the chemical 4-MI.
"While we believe that there is no public health risk that justifies any such change, we did ask our caramel suppliers to take this step so that our products would not be subject to the requirement of a scientifically unfounded warning," Garza-Ciarlante added.
In February, the Center for Science in the Public Interest (CSPI), a consumer advocacy group focusing on nutritional education and awareness, filed a petition with the US Food and Drug Administration (FDA) to ban the use of the caramel colouring compound.
A FDA spokesman said that the petition is being evaluated, but noted that an individual would have to consume more than 1,000 cans of soda a day to reach the same dose of the cancer-causing compound administrated in the studies to the lab mice and rats.
Image: The caramel colour used in sodas contains a compound called 4-methylimidazole, which was linked to tumours in rodents, even though similar effects in humans have not been proved. Photo:The Coca Cola Company